Prof. Samuel G. Paikowsky

Transcription

1 Drilled Deep Foundations Spring 2014 Lecture 2 - SUBSURFACE EXPLORATION AND SOIL PARAMETERS Prof. Samuel G. Paikowsky Geotechnical Engineering Research Laboratory University of Massachusetts Lowell USA Drilled Deep Foundations Spring 2014 Lecture 2 Part II Subsurface Explorations and Design Parameters Prof. Samuel G. Paikowsky Geotechnical Engineering Research Laboratory University of Massachusetts Lowell USA 2 1

2 Lecture Subjects Soil Origin and Deposition (Basic Review) N.E. Geology (Basic Review) Subsurface Exploration In-Situ Testing Design Parameters Drilled Deep Foundations Samuel Paikowsky 3 of 235 OBJECTIVES OF SUBSURFACE EXPLORATION Three General Objectives for Subsurface Exploration: 1. Define Soil and Rock Stratigraphy and Structure within Proposed Construction Zone of Influence. 2. Obtain Groundwater Data. - Level at Time of Testing. - Seasonal Fluctuations. 3. Determine Engineering Properties of Subsurface Materials for Use in Foundation Design. - Collect samples for laboratory testing. - Determine insitu engineering properties. Photograph courtesy of Drilled Deep Foundations Samuel Paikowsky 4 of 235 2

3 Subsurface Exploration PLANNING Subsurface Exploration Plan: Function of - Type and Critical Nature of Structure - Foundation Loads - Topographical Information - Site Geology (Soil and Rock Formations) - Location of Bedrock 1.5 m core to confirm >3 m core required for foundations on rock - Engineer s Experience - Project Requirements USACE EM There are no hard and fast rules stating the number and depth of samples for a particular geotechnical investigation. ASTM D420-98(2003) Standard Guide to Site Characterization for Engineering, Design, and Construction Purposes Consequences of Poor Subsurface Explorations (photographs courtesy of NHI 13231) Drilled Deep Foundations Samuel Paikowsky 5of 235 Subsurface Exploration PLANNING IBC (2009) Section (8 th Edition of MSBC) The scope of the soil investigation including the number and types of borings or soundings, the equipment used to drill and sample, the in-situ testing equipment and the laboratory testing program shall be determined by a registered design professional. YOU WILL NEED 1 BORING TO 100 ft TO DETERMINE SEISMIC SITE CLASSIFICATION FOR IBC 2006 Are Soil Explorations as Costly as the Repair? (Photographs courtesy of Drilled Deep Foundations Samuel Paikowsky 6 of 235 3

4 Subsurface Exploration PLANNING Photograph courtesy of TTU Center for Multidisciplinary Research in Transportation ( The Massachusetts State Building Code (7 th Edition) 780 CMR FOUNDATION AND SOILS INVESTIGATIONS Borings, Sampling and Testing. The scope of the subsurface exploration, including the number and types of borings, soundings or test pits, the equipment used to drill and sample, the in-situ testing equipment and the laboratory testing program, shall be determined by a registered design professional Drilled Deep Foundations Samuel Paikowsky 7 of 235 Subsurface Explorations Although the foundations are usually hidden from sight when the structure is complete, their performance has a profound effect on the overall performance of the structure. Karl Terzaghi (1951) ( ) has said: On account of the fact that there is no glory attached to the foundations, and that the sources of success or failure are hidden deep in the ground, building foundations have always been treated as step-children, and their acts of revenge for the lack of attention can be very embarrassing. Pisa Tower (From "Soil Mechanics" by Lamb & Whitman (1969), Chapter 14, p. 201) Drilled Deep Foundations Samuel Paikowsky 8 of 235 4

5 Subsurface Explorations Pisa Tower ( "Soil Mechanics" by Lamb & Whitman (1969), Chapter 14, p. 201) Drilled Deep Foundations Samuel Paikowsky 9 of 235 Subsurface Explorations Drilled Deep Foundations Samuel Paikowsky 5

6 Subsurface Explorations Drilled Deep Foundations Samuel Paikowsky 11 of 235 Subsurface Explorations Background Investigation of the underground conditions at a site is prerequisite to the economical design of the substructure elements. The cost of site exploration ranges between 0.5 to 1% of the total construction cost and it s elimination compared to the risk of subsequent damage and safety is false economy. The required knowledge depends on the structure type, which can be divided into 3 categories: Drilled Deep Foundations Samuel Paikowsky 12 of 235 6

7 Subsurface Explorations I) Main function is interaction with the surrounding ground Shallow Not to Scale Sheet pile Gravity Deep Foundations Tunnel (liner) Retaining Walls Main interest: Load - deformation relations of the loaded interfaces Soil - Structure interaction Drilled Deep Foundations Samuel Paikowsky 13 of 235 Subsurface Explorations I) Structures constructed from earth: highway fills and approach embankments, earth and rockfill dams, backfill behind walls Approach Embankment Dam Main interest: Properties of the construction material to determine the action of the earth structure itself and soil-structure interaction Drilled Deep Foundations Samuel Paikowsky 14 of 235 7

8 Subsurface Explorations Background (cont d.) III) Structures of natural earth and rocks, e.g., natural slopes Main interest: Knowledge of the properties of the natural materials in the natural state Drilled Deep Foundations Samuel Paikowsky 15 of 235 Subsurface Explorations Type of Subsurface Information Required for Design 1. Dimensions Areal extend, depth and thickness of each identifiable soil stratum within a depth, which depends on the structures size and nature as well as type of predominant soil. 2. Rock Depth to top of rock and character of the rock 3. Groundwater Location, fluctuation, possible artesian pressures and the flow regime 4. Engineering Properties In situ properties of the soil and/or rock such as permeability, compressibility, and shear strength Drilled Deep Foundations Samuel Paikowsky 16 of 235 8

9 Subsurface Explorations Obtaining Subsurface Information Two broad categories for exploration methods: Direct Method and Indirect Method Indirect Methods: Geologic mapping Aerial photography Topographic map interpretation Existing data - geological reports, maps, etc. Hydrological information by US Corps. of Eng. - soils surveys, etc. Highway Dept. Manuals Records of flow, etc. Websites: Google Maps and satellite options, Google Earth Typical conditions, e.g. the reference E.G. Johnson, Geotechnical Characteristics of the Boston Area, Civil Engineering Practice, Journal of BSCE section ASCE, vol. 4, no. 1, Spring 1989, pp Drilled Deep Foundations Samuel Paikowsky 17 of 235 Subsurface Explorations Obtaining Subsurface Information (cont d.) Two broad categories for exploration methods: Direct Method and Indirect Method Direct Methods: Field reconnaissance including examination of exposed materials in natural and man-made exposures Sounding and probing and in-situ monitoring during and after construction Borings, test pits, trenches, shafts obtaining representative disturbed and/or undisturbed samples of in-situ material Simple field tests - SPT and CPT for correlations with engineering properties Field tests - vane shear test, seepage and water pressure, plate bearing test, pile load test. Measuring directly the engineering properties of the in-situ materials Drilled Deep Foundations Samuel Paikowsky 18 of 235 9

10 Subsurface Explorations Subsurface Explorations 10

11 Subsurface Explorations Drilled Deep Foundations Samuel Paikowsky Subsurface Explorations 11

12 Subsurface Explorations Mass Building Code Section Foundation Investigations (p.23 of Review & Codes Class Notes, Volume 1) Where required: Boring, tests, drill holes, core borings or any combination shall be required for all structures except the following, unless specifically required by the building official: 1. One and two family dwellings and their accessory buildings; 2. Structures less than 35,000 cubic feet in gross volume; and 3. Structures used for agricultural purposes. The borings, test, pits or other soil investigations shall be adequate in number and depth and so located to accurately define the nature of any subsurface material necessary for the support of the structure. When it is proposed to support the structure directly on bedrock, the code official shall require core borings to be made into the rock, or shall require other satisfactory evidence to prove that the structure shall be adequately founded on bedrock Drilled Deep Foundations Samuel Paikowsky 23 of 235 Subsurface Explorations Mass Building Code Section Foundation Investigations (p.23 of Review & Codes Class Notes, Volume 1) Soil samples and boring reports: Samples of the strata penetrated in test borings or test pits, representing the natural disposition and conditions at the site, shall be available for examination by the code official. Wash or bucket samples shall not be accepted. Duplicate copies of the results obtained from all borings and of all test results or other pertinent soil data, shall be filed with the code official Note: Previous code specifically used the language of borings plotted to a true relative elevation and to scale Drilled Deep Foundations Samuel Paikowsky 24 of

13 Subsurface Explorations GENERAL SUBSURFACE INVESTIGATION METHODS METHOD Abbrv. ASTM SAMPLING MAX. DEPTH (ft) Hand Auger Borings HAB D a D (06) Yes Test/Excavation Pits TP None Yes Soil Test Borings STB D420-98(03) D a D (06) Yes Typ (w/difficulty) Limits of equipment (Typ. 20 ft) ~ 300 ft (dependent of various factors) D420-98(2003) Standard Guide to Site Characterization for Engineering, Design, and Construction Purposes Green Near Surface : Red Near and Deep Drilled Deep Foundations Samuel Paikowsky 25 of 235 Subsurface Explorations HAND AUGER BORINGS (HAB) Requires Manual Labor. Typical Depths up to 6 to 8 ft. Standard Diameter: 3¼ in (Other Diameters Available). Allows for soil samples (disturbed) to be collected for classification and laboratory testing (if desired). Typical HAB Cross-Section Figure courtesy of WPC Engineering Inc. Two Man Operation Photograph courtesy of Drilled Deep Foundations Samuel Paikowsky 26 of

14 Subsurface Explorations TEST/EXCAVATION PITS (TP) Photographs courtesy of photos.orr.noaa.gov, & Requires Appropriate Construction Equipment (e.g. backhoe). Typical Depths up to 20 ft (limited by equipment). Pit size determined by needs. Allows for soil samples (disturbed) to be collected for classification and laboratory testing (if desired). Allows for greater examination of insitu soils by geotechnical engineers and engineering technicians Drilled Deep Foundations Samuel Paikowsky 27 of 235 Subsurface Explorations SOIL TEST BORING (STB) RIGS Failing Truck Mounted Rig CME750 All-Terrain Rig Photographs courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 28 of

15 Subsurface Explorations SOIL TEST BORING (STB) RIGS MoDOT Track Mounted Rig Water Boring from Barge for Bridge Crossing Wireline Rig for Kaolin Mines Macon, GA Photographs courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 29 of 235 Subsurface Explorations SOIL TEST BORING (STB) RIGS Near Shore Water Boring Using a Jack-up Barge Photograph courtesy of Drilled Deep Foundations Samuel Paikowsky 30 of

16 Subsurface Explorations Planning the Exploration Program A. General 1. Methods are applicable for any structure or development. The difference is in the scope and detail. 2. Our focus is on exploration for buildings and structures where the cost per unit area is high = compact site. (In this class we refer mostly to shallow foundations). 3. Our aim is to obtain maximum amount of information at minimum cost. General rule of thumb, cost of exploration is.5 to 1.0% of total construction cost. o Lower for large project, homogeneous subsurface o Higher for smaller project, highly varied subsurface Drilled Deep Foundations Samuel Paikowsky 31 of 235 Subsurface Explorations Planning the Exploration Program A. General (cont d.) * It is justifiable to spend additional money on explorations and related testing as long as the savings in the construction cost on the basis of the obtained information are significantly greater, i.e., in some cases, no amount of detailed information may change the type, cost, or performance of the foundation. High Subsurface complexity Low lowest large Project size small highest Relative cost of subsurface exploration as a function of project size and subsurface complexity Drilled Deep Foundations Samuel Paikowsky 32 of

17 Subsurface Explorations Planning the Exploration Program (cont d.) B. Steps in Planning a Subsurface Exploration Program 1. Assemble all available information on the structure: dimensions, column spacing, type of structure, use of building, basement requirement, special architectural considerations (e.g., sensitive facade) and loads Approximation of 10 KN/m 2 /floor 1 ton/ m 2 /floor Column spacing 10 stories = 10 ton/m 2 e.g.: spacing = 6x6m, Max column load = 36m 2 x(10 ton/ m 2 ) = 360 tons 2. Assemble all available information on the site utilizing indirect methods, field reconnaissance, and available data from nearby structures, etc Drilled Deep Foundations Samuel Paikowsky 33 of 235 Subsurface Explorations Planning the Exploration Program (cont d.) B. Steps in Planning a Subsurface Exploration Program 3. Preliminary site investigation (usually the only investigation on standard jobs) From Stage 1: Loads concentration From Stage 2: Possible subsurface condition From 1+2 Possible foundation scheme Establish: (i) if the possible foundation requires test pits and/or borings. (ii) the number and depth of the test pits and/or borings 4. Depth and Number of Explorations o Should always include the influence zone of the foundation o One boring, usually the first, should get more data like extending it all the way to the bedrock (also in middle) Drilled Deep Foundations Samuel Paikowsky 34 of

18 Subsurface Explorations Planning the Exploration Program (cont d.) B. Steps in Planning a Subsurface Exploration Program 4. Depth and Number of Explorations Depth of Borings v Rules of Thumb o D (3 to 4) M M - smallest foundation dimension o D (1.5 to 2) smaller dimension of building o D not less than 6m (for very. small building) to 15m D 1 = depth at which = 0.1 q contact q contact Drilled Deep Foundations Samuel Paikowsky 35 of 235 Depth v 0.05 Subsurface Explorations Planning the Exploration Program (cont d.) B. Steps in Planning a Subsurface Exploration Program 4. Depth and Number of Explorations The smaller of D 1 and D 2 is used to approximate the minimum required depth of the boring (unless bedrock is encountered). See Table on page 76 (text): Number of stories and width of building for boring depth. Office Buildings and Hospitals (See equations 2.1, 2.2, 2.3, & 2.4) D b = (10 to 20)S 0.7 where D b (ft.) and S is No. of stories 10 for light steel or narrow concrete building and 20 for heavy steel or wide concrete building Drilled Deep Foundations Samuel Paikowsky 36 of

19 Subsurface Explorations Planning the Exploration Program (cont d.) B. Steps in Planning a Subsurface Exploration Program 4. Depth and Number of Explorations example: S = 1, D b = S = 3, D b = S = 10, D b = Spacing - Table 2.4, pg. 77 (text) Multi-story One-story Highways Subdivisions Dams and Dikes ft ft ft ft ft Lower values relate to complex subsurface and high values relate to homogeneous subsurface Drilled Deep Foundations Samuel Paikowsky 37 of 235 Subsurface Explorations Planning the Exploration Program (cont d.) B. Steps in Planning a Subsurface Exploration Program 4. Depth and Number of Explorations o The minimum is the number of borings that can be made in one drilling day, but try not less than 5 boreholes in the following configuration: Uniform soil less borings and more physical properties Drilled Deep Foundations Samuel Paikowsky 38 of

20 Subsurface Explorations Planning the Exploration Program (cont d.) B. Steps in Planning a Subsurface Exploration Program 5. Obtained Information: Stratification of soil (type and geometry), groundwater table (establish wells and piezometers for monitoring), rock or competent strata, sample recovery, field tests (usually SPT and/or vane tests) Small sites - you should be present to alter requirements based on initial findings, undisturbed samples are not usually obtained. 6. Detailed or Additional site investigation Locating additional borings based on missing information or design requirements Determine the need for additional sampling, especially undisturbed samples Consider construction procedures Drilled Deep Foundations Samuel Paikowsky 39 of 235 Subsurface Explorations Subsurface Test Layout General Guidelines FHWA (NHI ) USACE (Table 2-4 EM ) NAVFAC (DM7.01) Structure Min. # Spacing Min. # Spacing Min. # Spacing Rigid Frame Structure 1 per 230m² 50 ft spacing Low-Load Warehouse Corners Isolated Rigid Ftg < 2500ft² O.C. Isolated Rigid Ftg < 10,00ft² 3 around Per. Houses Subdivisions 1 per 8000m² 200 to 400 ft Houses Individual Lots 1 per lot Bridge Piers 1 (< 30m wide) 2 (> 30m wide) 1 Retaining Walls 1 60 m Roads 2 Lane 60 m 1 per 150 CL Roads Multi Lane 1 per 75 CL Cuts and Embankments 1 60 m Culverts 1 60 to 120 m Levees 6 to 12 m high 230 m Levees 12 to 18 m high 150 m 100 to 200 ft Drilled Deep Foundations Samuel Paikowsky 40 of

21 Subsurface Explorations SUBSURFACE TEST LAYOUT GUIDELINES SCDOT Geotechnical Design Manual (2010) Foundation Type Min. Geotechnical Site Investigation Reference Bridge Pile Foundation Minimum one testing location per bent 1 Table 4-1 Bridge Single Foundation Drilled Shaft Minimum one testing locations per foundation location Table 4-1 Bridge Multiple Foundation Drilled Shaft 2 Minimum two testing locations per bent location Table 4-1 Bridge Shallow Foundation Founded on Soil Minimum three testing locations per bent location Table 4-1 Bridge Shallow Foundation Founded on Rock Minimum two testing locations per bent location Table 4-1 Retaining Wall (within 150 of bridge abutment) Minimum one testing location at least every 75 ft Section Retaining Wall (within 150 of bridge abutment) Minimum one testing location at least every 75 ft Section Embankments Minimum one testing location at least every 500 ft Section Cut Excavations Minimum one test locations every 300 ft along cut area Section Culverts Minimum one testing each end of culvert and at every 100 ft of new crossline culvert 2 Section Sound Barrier Walls Dependant on shallow or deep foundation used 2 Section Misc. Structures (Light poles, overhead signs) Minimum of one test location per foundation location Section NOTES: 1. Spacing between testing locations may be increased, but shall be approved prior to field operations and shall include justification. Spacing may not exceed 100 ft. 2. See SCDOT Geotechnical Manual for additional details. Subsurface Explorations SUBSURFACE TEST DEPTH GUIDELINES Structure FHWA (NHI ) USACE (Table 2-4 EM ) Spread Footings Deep Foundations (Soil) Deep Foundations (Rock) L f 2B, Min. Depth = 2B L f 5B, Min. Depth = 4B 2B < L f < 5B, Extrapolate Min. Depth = 6m below anticipated foundation tip elevation Min. Depth = 3m, 3D, or 2B group below foundation tip Min. Depth = 1½B (4.5m for houses or to unweathered rock) Min. Depth = 1½B of imaginary 2/3 expected pile depth Roadways Min. 2m Min. 3m below finished grade (0.75m into rock) Embankments/Culverts Min. 2x Embankment Height Height of Levee Cuts Min. 5m below cut elevation NOTE: B = Footing Width Drilled Deep Foundations Samuel Paikowsky 42 of

22 Subsurface Explorations SUBSURFACE TEST DEPTH GUIDELINES SCDOT Geotechnical Design Manual (2010) Foundation Type Minimum Depth Reference Deep Foundation Bridge Shallow Foundation Retaining Walls Embankments Cut Excavations Culverts Borings shall extend below the anticipated pile or drilled shaft tip elevation a minimum of 20 ft or a minimum of 4 times the minimum pile group dimension, whichever is deeper. L 2B, Minimum test depth = 2B L 5B, Minimum test depth = 4B 2B L 5B, Minimum test depth = 3B At least 2X wall height beneath the anticipated bearing elevation or to auger refusal, whichever is shallower. At least 2X embankment height beneath the anticipated bearing elevation (i.e. to a depth sufficient to characterize settlement and stability issues) or to auger refusal, whichever is shallower. At least 25 feet below the anticipated bottom depth of the cut or to auger refusal, whichever is shallower. At least 2X the embankment height beneath the anticipated bearing elevation or in accordance with the bridge spread footing criteria, whichever is deeper (or auger refusal) Section Table 4-2 Section Section Section Section Sound Barrier Walls Dependant on shallow or deep foundation used 1 Section Misc. Structures (Light poles, overhead signs) Same depth criteria as specified for the bridge test locations for the same type of foundation. Section NOTES: 1. See SCDOT Geotechnical Manual for additional details Drilled Deep Foundations Samuel Paikowsky 43 of 235 Subsurface Explorations Other Useful Data: - North Arrow - Topographic Information TEST LOCATION PLAN (EXAMPLE) Shows test locations relative to site Symbol key differentiates between test types Project Information Scale Test Location Plan Example (Courtesy of Dr. Edward Hajduk and WPC Inc.) 22

23 Subsurface Explorations EXAMPLE FOR SITE INVESTIGATION PLAN Courtesy of G.Y.A., Ltd Drilled Deep Foundations Samuel Paikowsky 45 of 235 Subsurface Explorations EXAMPLE FOR SITE INVESTIGATION PLAN (cont d.) Courtesy of G.Y.A., Ltd Drilled Deep Foundations Samuel Paikowsky 46 of

24 Subsurface Explorations EXAMPLE FOR SITE INVESTIGATION PLAN (cont d.) Courtesy of G.Y.A., Ltd Drilled Deep Foundations Samuel Paikowsky 47 of 235 Soil Borings Definition A hole drilled in the ground (horizontal, vertically or inclined) for the primary purpose of obtaining samples of the overburden or rock materials present, in order to determine the stratigraphy and/or engineering properties of those materials. The hole may also be used for determination of engineering properties as permeability, shear strength, compressibility, etc. Hollow stem auger used by a truck mounted rig Drilled Deep Foundations Samuel Paikowsky 48 of

25 Soil Borings Equipment Used for Drilling Borings Most common - continuous flight auger: mostly hollow (can be solid) stem augers, (see Figures text pp ) The hollow stem auger consists of: 1) seamless steel tube with a spiral flight to which are attached a finger type cutter head at the lower end and an adapter cap at the top, (see Figures 2.11 and 2.13) ID 2.5 to 6 inches (SPT O.D = 2 inches) 2) a center drill stem composed of drill rods which are attached with a drag bit at the lower end and an adapter at the top Drilled Deep Foundations Samuel Paikowsky 49 of 235 Soil Borings Equipment Used for Drilling Borings continuous flight auger 5ft typ. Inside Diameter 2½ 6 SPT outer Diam. = 2 Sampling Tubes < Drilled Deep Foundations Samuel Paikowsky 25

26 Soil Borings Equipment Used for Drilling Borings The adapters at the top of the drill stem and auger flight are designed to permit advancement of the auger with the plug in place. As the hole is advanced, additional lengths of hollow stem flight and center stem are added as required, each length is usually 5ft. (3 to 6 ft. are possible) The flight acts as a screw conveyer to bring soil to the surface for up to 100m Method applicable in all soils. Difficulties occur in saturated sands under deep hydrostatic pressure where quick conditions at the bottom may destroy the boring Drilled Deep Foundations Samuel Paikowsky 51 of 235 Soil Borings SOIL TEST BORINGS (STB) Hollow Stem Augers (HSA) Continuous hollow flight augers, added in 5 ft increments. Hollow stem augers allow soil sampling without removal. Act as temporary casing to stabilize borehole. Center stem and plug are inserted down the hollow center during boring advance. HSA range from about 6 to 12 inch O.D. with 3 to 8 inch I.D. HSA generally limited to depths < 100 ft. HSA should not be used in loose silts and sands below the GWT. Truck-Mounted Rig with Hollow-Stem Augers HSA outer and inner assembly with stepwise center bit Text & Photographs courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 52 of

27 Soil Borings SOIL TEST BORINGS (STB) Solid Flight Augers Continuous flight augers, added in 5-ft increments. Limited to non-caving soils and depths < 30 ft. Solid flight augers are removed prior to soil sampling, thus laborintensive. Auger diameters from 4 in to 8 in. Front end has finger or fishtail bit to loosen soil. Spoil collects around top of borehole. Solid Auger and Drill Bit Text & Photographs courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 53 of 235 Soil Borings SOIL TEST BORINGS (STB) Solid Flight Augers Photographs courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 54 of

28 Soil Borings SOIL TEST BORINGS (STB) Rotary Wash Borings Rotary wash techniques are best for borings extending below GWT. Rotary wash can achieve great depths > 300+ ft. Drilling bits: Drag bits for clays Roller bits for sand In rotary wash method, borehole is stabilized using either temporary steel casing or drilling fluid. Fluids include water, bentonite or polymer slurry, foam, or Revert that are re-circulated in tub or reservoir at surface. Truck Rig conducting rotary wash boring Text & Photographs courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 55 of 235 Soil Borings SOIL TEST BORINGS (STB) Rotary Wash Borings Schematic (Hvorslev 1948) Photographs courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 56 of

29 Soil Borings SOIL TEST BORINGS (STB) Bucket Auger Borings Bucket auger drills are used for obtaining large disturbed or undisturbed samples. Diameters range from 0.6 m (2 ft) to 1.2 m (4 ft). Increment of 0.3 m to 0.6 m depths (1 to 2 feet). Good for gravelly soils and cobbles. Same rigs used for constructing Drilled Shafts. Setup of rig for Bucket Auger Boring (ASTM D4700) Text and Figure courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 57 of 235 Disturbed Sampling (Most Common) Bulk samples (from auger cuttings or TP excavations). Bucket samples (borrow pits). Drive samples (e.g. split-spoon). Laboratory Tests: Grain size, Atterberg Limits, Specific Gravity, Organic Content, Hydraulic Conductivity (coarse grained), Shear Strength (coarse grained). Most of the disturbed soil samples are obtained through the SPT. Limited use can be made by data obtained through cutting open a clayey sample and testing it with pocket penetrometer and torque vane. Split Spoon Sampler Undisturbed Sampling (ASTM D1587) Push Tubes (e.g. Shelby, Piston, Laval) Rotary & Push (e.g. Denison, Pitcher) Block Samples Laboratory Tests: Consolidation, Hydraulic Thin Wall Samplers Conductivity (cohesive), Shear Strength (cohesive) Text & Photographs courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 58 of

30 from Insitu Testing q Soil Density/Consistency N t (MPa) SANDS COHESIVE SOILS Soil Engineering Property Correlations t (pcf) after Fang et al. (1991) and EM NOTE: 1 MPa = tsf Drilled Deep Foundations Samuel Paikowsky 59 of 235 ( ) V. Loose <30 Loose Medium Dense Dense Very Dense >50 > Very Soft Firm Stiff Very Stiff Hard >30 > NA Soil Engineering Properties Determination Maximum Allowable Shear Strengths (SCDOT, 2010) Drilled Deep Foundations Samuel Paikowsky 60 of

31 Soil Engineering Properties Determination Maximum Allowable Shear Strengths (SCDOT, 2010) Drilled Deep Foundations Samuel Paikowsky 61 of 235 Coefficient of Variation (V) for Geotechnical Properties and Insitu Tests (after Duncan, 2000) Coefficient of Variation: A measure of dispersion of a probability distribution. Measured or Interpreted Parameter V (%) Unit Weight ( ) 3 to 7 Effective Friction Angle ( ') 2 to 13 Undrained Shear Strength (S u ) 13 to 40 Undrained Shear Ratio (S u / ' vo ) 5 to 15 SPT N Value 15 to 45 Electric CPT Tip Resistance (q t ) 5 to 15 after Table 52. FHWA IF Also see Chapter 8 Applying Judgement in Selecting Soil and Rock Properties for Design (FHWA IF ) Drilled Deep Foundations Samuel Paikowsky 62 of

32 Soil Borings Determination of Soil Stratigraphy Figure 9-1. FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 63 of 235 STANDARD PENETRATION TEST (SPT) (ASTM D a) Marking of 6 inch Increments for SPT Test Photograph courtesy of physics.uwstout.edu Very common test worldwide Colonel Gow of Raymond Pile Co. Split-barrel sample driven in borehole. Conducted on 2½ to 5 ft depth intervals. ASTM D1586 guidelines Drop Hammer (140 lbs falling 30 inches) Three increments of 6 inches each; Sum last two increments = SPT N value" (blows/ft) Correlations available with all types of soil engineering properties. Disturbed Soil Samples Collected Text courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 64 of

33 General SPT - Standard Penetration Test Most economic and popular means to obtain subsurface information in the USA Split Spoon Sampler ASTM D (text p. 81, Fig. 2.15). Thick wall sampler O.D = 2 inch, I.D. = 1 3/8 inch (See ASTM D , attached p. 59 of the notes) Using a 140lb. hammer falling 30 to drive a split-barrel sampler 18 inch into the soil. Count the number of blows required to drive the sampler 6 (3 times) The test result, N SPT = number of blows required for the sampler to penetrate the last 12 (from 6 to 18 inch penetration) Drilled Deep Foundations Samuel Paikowsky 65 of 235 SPT - Standard Penetration Test General Example Blows/ Boring WOR Stop test & mark boring log by refusal if: 50 blows required for any 6 15 Obtain 100 blows from the beginning In 10 successive blows, there is no evidence of movement Usually measure distance and number, e.g. 40b/2 meaning 40 blows measured along 2 inches. When the sampler penetrates under its own weight (and rods) mark WOR = weight of rods 10 4 ob / Drilled Deep Foundations Samuel Paikowsky 66 of

34 STANDARD PENETRATION TEST (SPT) (ASTM D a) Split Spoon Dimensions (after ASTM D1586) Typical Setup Figures courtesy of J. David Rogers, Ph.D., P.E., University of Missouri-Rolla & FHWA NHI Course Drilled Deep Foundations Samuel Paikowsky 67 of 235 STANDARD PENETRATION TEST (SPT) (ASTM D a) Figure courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 68 of

35 STANDARD PENETRATION TEST (SPT) (ASTM D a) TEST RESULTS (i.e. BORING LOG) Shows the following: Soil Profile (determined from sampling and boring information) with respect to depth and/or elevation. Groundwater Table (GWT). SPT N Values. Laboratory Test Results (if available). ASTM D Standard Guide for Field Logging of Subsurface Explorations of Soil and Rock Boring Log courtesy of Dr. Edward Hajduk and WPC Engineering Inc Drilled Deep Foundations Samuel Paikowsky 69 of 235 STANDARD PENETRATION TEST (SPT) (ASTM D a) TEST RESULTS (i.e. BORING LOG) Class Project Boring Log (pg1/3) Drilled Deep Foundations Samuel Paikowsky 70 of

36 STANDARD PENETRATION TEST (SPT) (ASTM D a) TEST RESULTS (i.e. BORING LOG) Class Project Boring Log (pg2/3) Drilled Deep Foundations Samuel Paikowsky 71 of 235 STANDARD PENETRATION TEST (SPT) (ASTM D a) TEST RESULTS (i.e. BORING LOG) Class Project Boring Log (pg3/3) Drilled Deep Foundations Samuel Paikowsky 72 of

37 SPT - Standard Penetration Test Factors Affecting the SPT a. Overburden pressure b. Energy approaching the bottom scientific factors c. Driving shoe condition d. Hitting on a stone e. Quick conditions in the hole bottom by too rapid withdrawal of auger or bit plug or from the SPT (liquefaction). f. Differential water level between GWL and the water inside the hollow auger. g. Method of hammer fall Energy production from automatic trip or rope on pulley Note: Factors c to g should be dealt by adequate procedures and inspection Drilled Deep Foundations Samuel Paikowsky 73 of 235 STANDARD PENETRATION TEST (SPT) Factors Affecting SPT (after Kulhawy & Mayne, 1990 & Table 8. FHWA IF ) Cause Inadequate Cleaning of Borehole Effects SPT not made in insitu soil, soil trapped, recovery reduced Influence on N Value Increases Failure to Maintain Adequate Head in Borehole Bottom of borehole may become quick Decreases Careless Measure of Drop Hammer Energy varies Increases Hammer Weight Inaccurate Hammer Energy varies Inc. or Dec. Hammer Strikes Drill Rod Collar Eccentrically Hammer Energy reduced Increases Lack of Hammer Free (ungreased sleeves, stiff rope, more than 2 turns on cathead, incomplete release of drop, etc.) Hammer Energy reduced Increases Sampler Driven Above Bottom of Casing Sampler driven in disturbed soil Inc. Greatly Careless Blow Count Recording Inaccurate Results Inc. or Dec. Use of Non-Standard Sampler Correlations with Std. Sampler Invalid Inc. or Dec. Coarse Gravel or Cobbles in soil Sampler becomes clogged or impeded Increases Use of Bent Drill Rods Inhibited transfer of energy to sampler Increases Drilled Deep Foundations Samuel Paikowsky 74 of

38 CORRECTIONS TO SPT N VALUE N measured = Raw SPT Value from Field Test (ASTM D a) N 60 = Corrected N values corresponding to 60% Energy Efficiency (i.e. The Energy Ratio (ER) = 60% (ASTM D ) Note: 30% < ER < 100% with average ER = 60% in the U.S. N 60 = C E C B C S C R N measured SPT Corrections From Table 9 FHWA IF Factor Term Equipment Variable Correction Energy Ratio C E = ER/60 Donut Hammer Safety Hammer Automatic Hammer Borehole Diameter C B 150 mm mm 200 mm Standard Sampler Sampling Method C S Non-Standard Sampler 3 4 m Rod Length C R 4 6 m 6 10 m > 10 m 0.5 to to to to For Guidance Only. Actual ER values should be measured per ASTM D Drilled Deep Foundations Samuel Paikowsky 75 of 235 SPT - Standard Penetration Test Adjusting the SPT results for Standard Readings 1. Energy m h E in = E p = m g h E in = 63.5Kg 9.807m/sec m = 474.5kN. m =140lb. 2.5ft = 350lb. ft (Joul) E r = efficiency = (input) x 100% = 30% to 80% Drilled Deep Foundations Samuel Paikowsky 76 of

39 SPT - Standard Penetration Test Adjusting the SPT results for Standard Readings 1. Energy (cont d.) Bowles suggests to use 70% Very common in other references, the standard SPT efficiency is considered to be 60% and, hence, N 60 is often used for correlations. E 1 x N 1 = E 2 N 2 N 2 = N 1 e.g. hammer efficiency E 1 = 55% N 1 = 25 N 70 = x 25 N 70 = 20 (19.6) or N 60 = x 25 N 60 = 23 (22.9) Drilled Deep Foundations Samuel Paikowsky 77 of 235 Depth (meters) CORRECTIONS TO SPT N VALUE EXAMPLE OF DATA FROM SAME SITE Donut Safety Measured N-values Sequence ER = 34 (energy ratio) Depth (meters) Corrected N Donut Safety Trend Data from Robertson, et al. (1983), Courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 78 of

40 SPT - Standard Penetration Test Adjusting the SPT results for Standard Readings 2. Overburden Pressure See text pp and attached paper: Overburden Correction Factors for SPT in Sand by Liao & Whitman (ASCE, J. Of Geotechnical Engineering, Sept. 1985, class notes pp ). C N - adjusting factor which is the ratio of SPT at a given effective vertical stress v to a standard stress level vref = 1 tsf = 1kg/cm 2 Say 18 kn/m 3 and no water, t = v 100 kn/m 2 D = 5.5m 15ft. C N = v in tsf or kg/cm 2 (1 tsf = kg/cm 2 ) Drilled Deep Foundations Samuel Paikowsky 79 of 235 SPT - Standard Penetration Test Adjusting the SPT results for Standard Readings 2. Overburden Pressure (cont d.) Or in a general format: C N = (P a / ' vo ) n P a = Atmospheric Pressure (1 atm = 14.7 psi = 2116 psf = 1.06 tsf) ' vo = Insitu Vertical Effective Stress n = 1 (clays) and 0.5 to 0.6 (sands) For stresses of v < 1 tsf the relations proposed by Skempton (1986) can be used (text equations 2.12 & 2.13). C N = v in tsf or kg/cm Drilled Deep Foundations Samuel Paikowsky 80 of

41 SPT - Standard Penetration Test Adjusting the SPT results for Standard Readings 3. Other Corrections are available including hammer type, rod length, sampler (with or without a liner), borehole diameter correction and others. On the whole, the accuracy and necessity of these corrections are questionable and their importance is secondary to the above two controlling factors and a standard procedure 4. The standard blow count to be used for correlations is: N corr = N 60 x C N N 60 = N x X = the energy during test and C N to be used for granular materials Note: N corr is also represented by (N 1 ) 60, N 1 or N Drilled Deep Foundations Samuel Paikowsky 81 of 235 CARE & PRESERVATION OF SOIL SAMPLES Mark and Log samples upon retrieval (ID, type, number, depth, recovery, soil, moisture). Place jar samples in wood or cardboard box. Should be protected from extreme conditions (heat, freezing, drying). Sealed to minimize moisture loss Packed and protected against excessive vibrations and shock. Text and Figures courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 82 of

42 SPT - Standard Penetration Test Correlations between SPT and Soil Parameters The SPT has been used in correlations for unit weight, relative density, angle of internal friction and undrained shear strength. All are empirical correlations with limited accuracy 1. SPT in Clay SPT is not recommended for clays Based on Mayne and Kemper (1988) Table 2.6 (p. 84) S u q u NOTE: N in clay does not require corrections to a standard effective stress (i.e. don t use C N ) Drilled Deep Foundations Samuel Paikowsky 83 of 235 SPT - Standard Penetration Test Correlations between SPT and Soil Parameters 2. SPT in Sand Table 2.8 (p. 87) of the text, simplified relations Table 2.8 Relation between the Corrected (N 1 ) 60 Values and the Relative Density in Sands Approximate relative density, D r,(%) Standard penetration number, (N 1 ) Equations 2.19 to 2.25 for a correlation between relative density and effective overburden stress Equations 2.26, 2.27 and 2.28 for a correlation between standard penetration number and friction angle Drilled Deep Foundations Samuel Paikowsky 84 of

43 SPT - Standard Penetration Test Correlations between SPT and Soil Parameters Some Additional Correlations Relative Density Bowles (1996) D R = / in kpa for O.C.R. sand D R = / C ocr ) Giuliani & Giuliani Nicoll (1982) C OCR = (1 + 2K oocr )/(1 + 2K onc ) D R = / ( ) v in t/m 2 = 10 kpa and N is uncorrected Drilled Deep Foundations Samuel Paikowsky 85 of 235 SPT - Standard Penetration Test Correlations between SPT and Soil Parameters Some Additional Correlations (cont d.) Friction Angle Teng (1962) = (25 o to 30 o ) D R D R in % Paikowsky (1982) = D R for Israeli dune sands Empirical values for, D r, and unit weight of granular soils based on the SPT at about 6m depth and normally consolidated [approximately, = D r ( 2 )] (Bowles, 1996) NOTE: Use N corr SPT values in the table Drilled Deep Foundations Samuel Paikowsky 86 of

44 SPT - Standard Penetration Test Correlations between SPT and Soil Parameters Some Additional Correlations (cont d.) NOTE: Use N corr SPT values in the table Description Very loose Loose Medium Dense Very dense Relative density D r SPT N 70 : fine medium coarse :fine medium coarse ? > 40 > 45 < 50 wet, kn/m * *Excavated soil or material dumped from a truck has a unit weight of 11 to 14 kn/m 3 and must be quite dense to weigh much over 21 kn/m 3. No existing soil has a D r = 0.00 nor a value of Common ranges are from 0.63 to Drilled Deep Foundations Samuel Paikowsky 87 of Paikowsky et al. NCHRP wet, (pcf) Medium (pcf)=1.03n'+109 Dense (pcf)=0.88n'+99 (pcf)=0.72n' Figure 3.1 -N Relationship for Sand (General Condition) Based on Bowles (1996) Loose N 70 ', (blow/ ft) Unit Weight vs. SPT for Sand Drilled Deep Foundations Samuel Paikowsky 88 of

45 SPT - Standard Penetration Test Correlations between SPT and Soil Parameters Some Additional Correlations (cont d.) Correlations of to N Hatanaka, M. & Uchida, A. (1996) Empirical correlation between penetration resistance and internal friction angle of sandy soils (Eq. 2.28) Peck, Hansen and Thornblum (1974) (Wolff, 1989 version) = N (N 60 ) 2 (Eq. 2.26) (Kulhawy and Mayne 1990 version) = Japan Road Association (JRA) (1990 & 1996) "Specifications for highway bridges, Part IV N > 5 and Drilled Deep Foundations Samuel Paikowsky 89 of 235 SPT - Standard Penetration Test N 1 = f HNU = f PHT = f K&M = f JRA = Soil friction angle, f (deg) PHT 1974 (Wolff, 1989) PHT (Kulhawy & Mayne, 1990) Hatanaka & Uchida (1996) SHB, Japan (JRA, 1996) Corrected SPT count, (N 1 ) Drilled Deep Foundations Samuel Paikowsky 90 of

46 Paikowsky et al. NCHRP Report 651 Table 30 Summary of equation correlating internal friction angle ( f ) to corrected (N 1 ) 60 SPT-N value Reference Correlation Equation Equation No. Peck, Hanson and Thornburn as mentioned in Kulhawy and Mayne (1990) (PHT (Kulhawy & Mayne, 1990) ) (100) f 20 N Hatanaka and Uchida (1996) (101) for 3.5 N 30 Peck, Hanson and Thornburn (1974) as mentioned by Wolff (1989) (PHT 1974 (Wolff, 1989)) Mayne et al. (2001) based on data from Hatanaka and Uchida (1996) Specifications for Highway Bridges (SHB) Japan, JRA (1996) exp N f (102) (103) (104) Drilled Deep Foundations Samuel Paikowsky 91 of f N N N 20 f N 15 f 1 60 for N 5 and 45 p a is the atmospheric pressure and v is effective overburden pressure in the same units. For English units, p a = 1 and v is expressed in tsf at the depth N 60 is observed. (N 1 ) 60 is the corrected SPT-N value corrected using the correction given by Liao and Whitman (1986): p (105) a N1 N ' v f Paikowsky et al. NCHRP Report Soil friction angle, f (deg) Corrected SPT count, (N 1 ) 60 PHT 1974 (Wolff, 1989) PHT (Kulhawy & Mayne, 1990) Hatanaka & Uchida (1996) Hatanaka & Uchida (Mayne et al, 2001) SHB, Japan (JRA, 1996) Figure 56. Comparison of various correlations between granular soil friction angle and corrected SPT blow counts (using the overburden correction proposed by Liao and Whitman (1986)) Drilled Deep Foundations Samuel Paikowsky 92 of

47 Gurbuz Thesis Figure 3.2 -N Relationship for Clay, pcf , kn/m Nuncorrected (blow/ft) Legend Key Soil Type Correlations Limit Reference Comment Lean Clay 1.02 N Lean Clay 9.33 LN ( N) Fat Clay 1.35 N Fat Clay LN ( N) Sandy or Silty Clay Silty Clay with stones or rock fragment 1.56 N pcf pcf pcf pcf pcf 1.2 N pcf Well-graded Gravel, Sand, 1.03 N pcf Silt & Clay mixture Organic Clay 1.46 N pcf Organic Silt 1.46 N pcf Terzaghi and Peck (1967), Bardet (1997) Terzaghi and Peck (1967), NAVFAC Design Manual (1986) Valid if the soil mixture is classified as clay, otherwise use the correlation established for sand. 11 Elastic Method 1. AASHTO LRFD Bridge Design Specifications (1998) (cont d.) Table 1. Elastic Constants of Various Soils Modified after U.S. Department of the Navy (1982) and Bowels (1988) (AASHTO Table b-1) Soil Type Typical Range of Values Poisson s Estimating E s from N Young's Modulus Ratio, (dim) (tsf) Soil Type E s (tsf) clay: soft sensitive Silts, sandy silts, slightly cohesive mixtures 4N 1 Medium stiff to stiff (undrained) Clean fine to medium sands & slightly silty sands 7N 1 Very stiff Coarse sands and sand with little gravel 10N 1 Sandy gravel and gravels 12N 1 Loss Silt Sandy gravel and gravels 12N Fine Sand: Estimating E s from S u Loose Soft sensitive clay 400S u -1,000S u Medium dense Medium stiff to stiff clay 1,500S u -2,400S u Dense Very stiff clay 3,000S u -4,000S u Sand: Loose Medium dense Dense Gravel: Estimating Es from q c Loose Medium dense 800-1,000 Sandy Soil 4q c Dense 1,000-2, Notes: N = Standard Penetration Test (SPT) resistance N 1 = SPT corrected for depth S u = undrained shear strength (TSF) q c = cone penetration resistance (TSF) Drilled Deep Foundations Samuel Paikowsky 94 of

48 Young's Modulus, E/P a LOOSE MEDIUM DENSE V.DENSE Recommended for Drilled Shafts Recommended for Driven Piles Driven piles Typical Young s Modulus of Sands (E s ) vs. Blow Count Measured or Corrected N (blows/ft or 305 mm) Legend Key Relations Soil Type Reference Comment General Sources, Es / pa 0.5( N 15) NC Sand N = N see Bowles (1996) 55 Es / pa 70 N NC Sand Denver (1982) N = N 55 USSR N should be estimated as N55, and N Es / pa 150ln( N) NC Sand (See Bowles, 1996) may not be standard blow count USSR N = N55. N may not be the standard Es / pa 220ln( N) NC Sand (See Bowles, 1996) blow count E / p Sands with Kulhawy & Mayne a 5N 60 fines (1990) E / p Clean NC Kulhawy & Mayne a 10N 60 Sand (1990) E / p Clean OC Kulhawy & Mayne a 15N 60 Sand (1990) Recommended by O Neill & Reese (1999) for use with drilled shaft 0.82 Piedmont Using Mayne & ED / pa 22N elastic analysis in cohesionless IGM. Sandy Silts Frost (1989) ED is the modulus measured in the dilatometer test (DMT) E / p Piedmont Mayne & Frost ED is replaced by Es through the a 20.02N Sandy Silts (1989) relation: ED=Es/(1-2 ), & =0.3. EPMT is the modulus measured in the 0.66 pressuremeter test (PMT), and is EPMT / pa 9.08N Sand Ohya, et al (1982) often presumed to be roughly equivalent to Young s modulus E. Current study For N>60 use N=60. Recommended Es / pa 200ln( N ) Sand Driven Piles for driven piles N Current study For N>60 use N=60. Curve best fit Es / pa 112e ln( N) Sand Drilled Shafts of all information for drilled shaft. For driven piles E s / p a = 200ln(N), N 60 For drilled shafts E s / p a = 112e 0.07 ln(n), N 60 where: p a = atmospheric pressure = 0.1 MPa E s = Young s modulus of soils N = corrected blow count in SPT tests for 60% energy and vertical effective stresses Paikowsky et al. NCHRP Report 651 Young s Modulus of Clay (E s ) vs. Undrained Shear Strength x10 6 1x10 6 Legend Key Relations Soil Type Reference Comment E s (100 ~ 500) s u Ip > 30 or organic General resource, Lines represent upper and see Bowles (1996) lower range. 1.0x10 5 1x10 5 E s (500 ~ 1500) s u Ip < 30 or stiff General resource, Lines represent upper and see Bowles (1996) lower range. Es Ks u 2 3 K I p 1.73I p I p General clay Use 20% Ip 100% and round General resource, K to nearest multiple of 10. see Bowles (1996) Lines represent upper and lower range. E s, kpa 1.0x10 4 1x10 4 Clay Clay Poulos & Davis (1990) Poulos & Davis (1990) For driven piles. Drained condition. For bored piles. Drained condition. E u ~ Soft clay Kulhawy & Mayne (1990) Lines represent upper and lower range. Undrained condition. 1.0x10 3 1x10 3 E u ~ Medium clay Kulhawy & Mayne (1990) Lines represent upper and lower range. Undrained condition. E u ~ Stiff clay Kulhawy & Mayne (1990) Lines represent upper and lower range. Undrained condition. E 200 Clay Current study s S u Reasonable approximation for all piles in clay 1.0x10 2 1x S u, kpa Paikowsky et al. NCHRP Report Drilled Deep Foundations Samuel Paikowsky 96 of

49 Young s Modulus - SUMMARY In Sand For driven piles E s / p a = 200ln(N), N 60 (6.2) For drilled shafts E s / p a = 112e 0.07 ln(n), N 60 (6.3) where: p a = atmospheric pressure = 0.1 MPa E s = Young s modulus of soils N = corrected blow count in SPT tests for 60% energy and vertical effective stresses Both equations are limited by the value of Es for N=60, i.e. for N>60 use N=60. The equation 6.3 has the combination of exponential and logarithmic formats to overcome the overestimation of E when N<10 and the underestimation of E when N>30. In Clay E s = 200S u (6.4) where: E s = Young s modulus of soils Paikowsky et al. NCHRP Report 651 S u = undrained shear strength Drilled Deep Foundations Samuel Paikowsky 97 of 235 Correlations between SPT and Soil Parameters EXAMPLE SPT - Standard Penetration Test Depth (ft.) 0 Find the soil parameters of //\\//\\\\////\\\\\//// the marked layer based on Fill the SPT results t = 120pcf 10.5 Silty Clay t = 118pcf GW Level =15ft Fine to Medium Sand Depth=25.0 ft. N=25 t = 120pcf Drilled Deep Foundations Samuel Paikowsky 98 of

50 Correlations between SPT and Soil Parameters SPT - Standard Penetration Test EXAMPLE (cont d.) Vertical effective stress at the depth of measurement: v = ( ) ( ). ( ) + ( ). ( ) = 2,356 psf = tsf = 118 kpa. = 11.8t/m 2 correction factor for the overburden: E r = 95% (measured efficiency) corrected blow count to the standard 60 or 70% efficiency: N 70 = (95/70) x 25 = 33.9 N 60 = (95/60) x 25 = 39.6 C N =. = (N corr ) 60 = 39.6 x = 36.4 = 36 blows (N corr ) 70 = 33.9 x = 31.3 = 31 blows Drilled Deep Foundations Samuel Paikowsky 99 of 235 Correlations between SPT and Soil Parameters SPT - Standard Penetration Test EXAMPLE (cont d.) When considering all other additional factors the corrected blow count can go up or down by one blow, in this particular case we use the final result of N = 31 blows for the correlations. Table correlation considering sand type Using Bowles table (notes p. 90): Dense Sand, D R 70%, = 38 Establishing relative density Using the equation by Bowles: % Using Giuliani & Giuliani Nicoll: 27/ % Drilled Deep Foundations Samuel Paikowsky 100 of

51 Correlations between SPT and Soil Parameters EXAMPLE (cont d.) Correlations = f(d R ) Using Teng: = 35 to 40 Using the correlation for Israeli dune sand = 38 SPT - Standard Penetration Test Correlations = f(n 60 ) Hatanaka and Uchida = 45 Using PH&T = 35.9 (Wolff), = 36.1 (Kulhawy & Mayne) Conclusions: 1. Using interpolated values in Bowles table provide a reasonable solution and allow grain size consideration. 2. Check several correlations to view range of results. 3. Experience showed PHT (Kulhawy & Mayne) to provide good and safe correlation of =f(n 1 ) Drilled Deep Foundations Samuel Paikowsky 101 of 235 EXAMPLE INTERPRETATION SPT Given Data Provided: - Soil Stratigraphy - USCS Classification - Groundwater Table (@ Time of Testing) - SPT N Values (No Energy Measurements) - Drilling Method (HSA) - Date Started/Ended Drilled Deep Foundations Samuel Paikowsky 102 of

52 Depth (ft) EXAMPLE INTERPRETATION SPT Determination of N ave, t, and ' vo SAND - Silty SAND N ave = 17 use t = 115 pcf Sandy SILT N ave = 4 use t = 110 pcf Depth (ft) Clayey SILT (MH)/MARL N ave = 4 use t = 115 pcf B-7 N (bpf) ' vo (psf) t from Table Soil Engineering Properties Correlations (pg. 69 of notes) Drilled Deep Foundations Samuel Paikowsky 103 of 235 Depth (ft) EXAMPLE INTERPRETATION SPT Determination of Effective Friction Angle ( ') SAND - Silty SAND N ave = 17 use t = 115 pcf Sandy SILT N ave = 4 use t = 110 pcf Clayey SILT (MH)/MARL N ave = 4 use t = 115 pcf B-7 N (bpf) Calculate N ave for sand layer from 0 to 8 ft. Simple Way: Using Soil Engineering Properties Correlations (pg. 69 of notes) N ave = 17, therefore ' 36 Formula Way: Use Mayne et al. (2001) ' = [15.4(N 1 ) 60 ] and (N 1 ) 60 = N 60 (P a / ' vo ) 0.5 Use N ave = 17, ' vo,ave = 460 psf, and P a = 2115 psf Therefore, (N 1 ) 60 = 17(2115/460) 0.5 = 36 Using equation ' = [15.4(N 1 ) 60 ] , ' = 44 USE ' = Drilled Deep Foundations Samuel Paikowsky 104 of

53 ASTM Standard D a ASTM Standard D a 53

54 ASTM Standard D a ASTM Standard D a 54

55 ASTM Standard D a ASTM Standard D a 55

56 ASTM Standard D a Drilled Deep Foundations Samuel Paikowsky 111 of 235 ASTM Standard D a 56

57 ASTM Standard D a Drilled Deep Foundations Samuel Paikowsky 113 of 235 ASCE Journal of Geotechnical Engineering Vol. 112, No. 3 March

58 ASCE Journal of Geotechnical Engineering Vol. 112, No. 3 March 1986 ASCE Journal of Geotechnical Engineering Vol. 112, No. 3 March

59 ASCE Journal of Geotechnical Engineering Vol. 112, No. 3 March 1986 ASCE Journal of Geotechnical Engineering Vol. 112, No. 3 March

60 Split-Spoon Disturbed Sampling Thin walled Tubes Undisturbed Sampling (ASTM D1587) Split Spoon Sampler Thin Wall Samplers Text & Photographs courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 119 of 235 Shelby Tubes Using a thin walled tubes (O.D. = 2in.) which is pushed into the soil under the bottom of the borehole in order to retrieve a sample mainly for laboratory tests. The sampling can be performed by a direct connection to the drill rods or using a piston sampler. (i) Piston closes the end of the sampler while it is lowered to the bottom of the borehole. (ii) The sampler is pushed hydraulically (iii) The pressure is released through a hole in the piston rod (iv) The assembly is pulled upwards Drilled Deep Foundations Samuel Paikowsky 120 of

61 Shelby Tubes Figure 2.18 (continued), text pp.90 & 93, respectively Drilled Deep Foundations Samuel Paikowsky 121 of 235 ASTM D Standard Practice for Thin-Walled Tube Sampling of Soils for Geotechnical Purposes 61

62 ASTM D Standard Practice for Thin-Walled Tube Sampling of Soils for Geotechnical Purposes ASTM D Standard Practice for Thin-Walled Tube Sampling of Soils for Geotechnical Purposes 62

63 ASTM D Standard Practice for Thin-Walled Tube Sampling of Soils for Geotechnical Purposes INSITU TESTING METHODS METHOD Abbrv. ASTM SAMPLING MAX. DEPTH (ft) Dynamic Cone Penetrometer DCP D Yes (via HAB) 6 8 Typ. 20 (w/difficulty) Standard Penetration Test SPT D a Yes > 300 ft (dependent on boring method) Cone Penetration Test CPT D D No > 300 ft (typically ft max) Flat Plate Dilatometer DMT D No > 300 ft (typically ft max) Pressuremeter PMT D Yes (via boring) Yes Vane Shear Test VST D (via Boring) Green Near Surface : Red Near and Deep > 300 ft (dependent on boring) > 300 ft (dependent on boring) Drilled Deep Foundations Samuel Paikowsky 126 of

64 INSITU TESTING METHODS Figure courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 127 of 235 Vane Shear Test (VST) (ASTM D ) General Vane shear test (ASTM D ) is a useful method to estimate the undrained shear strength of cohesive - soft soils, especially where much of the strength may be lost by disturbance during sampling. not good in stiff clays or soft soils containing gravel, shells etc Drilled Deep Foundations Samuel Paikowsky 128 of

65 VANE SHEAR TEST (VST) (ASTM D ) Performed at bottom of boring or by direct push placement of device Four-sided blade pushed into clays and silts to measure following: s uv (peak) = Peak Undrained Strength s uv (remolded) = Remolded Strength (after 10 revolutions) Sensitivity, S t = s uv (peak)/s uv (remolded) Scandinavian Vanes Pictures and text courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 129 of 235 VANE SHEAR TEST (VST) (ASTM D ) Procedure Placing a four-bladed vane in the undisturbed soil (under the bottom of the borehole) and rotating it from the surface to determine the (peak) torsional force (through torque) required to cause a cylindrical surface to be sheared by the vane. This force is then converted to a unit shearing resistance of the cylindrical surface. The test continues to measure the strength of the remolded material by measuring the resistance to the rotation after the vane is rotated rapidly through a minimum of 10 revolutions Drilled Deep Foundations Samuel Paikowsky 130 of

66 VANE SHEAR TEST (VST) (ASTM D ) Casing(OD) D(in) Blade thick Rod(in) AX (1 7 / 8 ) 1.5 1/16 1/2 BX (2 3 / 8 ) 2.0 1/16 1/2 NX (2 15 / 16 ) 2.5 1/8 1/2 Vane Dimensions 1.5 D 4 inch 1 D H 2.5 D Drilled Deep Foundations Samuel Paikowsky VANE SHEAR TEST (VST) (ASTM D ) Figure courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 132 of

67 VANE SHEAR TEST (VST) (ASTM D ) Vane Shear Devices Dutch Vane Equipment, Holland VST in Upstate NY Pictures courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 133 of 235 VANE SHEAR TEST (VST) (ASTM D ) Analysis Obtaining the consolidated (in-situ) undrained shear strength S uv : u=undrained, v=vane Torque peak T residual H=2D T=S uv A R 20 Movement (rotation in radians) D/2 T - Torque S uv - shear strength A- area of shear application R - arm of force Drilled Deep Foundations Samuel Paikowsky 134 of

68 VANE SHEAR TEST (VST) (ASTM D ) Analysis (cont d.) for the circumferential shearing area: A = D H R = D/2 A R = (D 2 H/2) for the top and bottom shearing area: A = D 2 /4 R = D 1/3 (2) = (2/3)D A R = (D 3 /4)(2/3) ⅔D x ½ ⅔D x ½ Drilled Deep Foundations Samuel Paikowsky 135 of 235 VANE SHEAR TEST (VST) (ASTM D ) Analysis (cont d.) Combining all shearing areas, leads to: T = S uv A R = S uv [(D 2 H/2) + D 3 /4 (2/3)] For the standard case in which H = 2D and square end shear, the above equation becomes: S uv = 6T/(7 D 3 ) = T/D 3 The general assumption is that vane test results are too high and require a correction. The reason can be the influence of the rate of shear, various frictional losses such that the measured torque is higher than the one actually performing the work and other assumptions in the above relations (e.g. stress distribution at the blade). S uvcorrected = S uv Drilled Deep Foundations Samuel Paikowsky 136 of

69 VANE SHEAR TEST (VST) (ASTM D ) Analysis (cont d.) see equations and figure below based on Bjerrum (1972) (equation 2.35, p. 97) Bjerrum (1972): % Morris & Williams (1994): (for PI>5) (where LL is in %) Aas et al. (1986): see figure Variation of with c u(vst) / Drilled Deep Foundations Samuel Paikowsky 137 of 235 VANE SHEAR TEST (VST) (ASTM D ) Estimation of OCR based on VST Based on Mayne and Mitchell (1988) [see text p. 97] p c = 7.04 (Su field ) 0.83 OCR = p c = maximum past pressure [kpa] Su field = uncorrected field vane value [kpa] (=Cu field ) = 22 (PI) (eq. 2.37) Drilled Deep Foundations Samuel Paikowsky 138 of

70 VANE SHEAR TEST (VST) (ASTM D ) Estimation of OCR based on VST (cont d.) Variation of with plasticity index (after Mayne and Mitchell, 1988) See other correlations for (equations 2.39, 2.40) Drilled Deep Foundations Samuel Paikowsky 139 of 235 VANE SHEAR TEST (VST) (ASTM D ) Drilled Deep Foundations Samuel Paikowsky 70

71 VANE SHEAR TEST (VST) (ASTM D ) Results - San Francisco Bay Mud, MUNI Metro Station 0 Vane Strength, s uv (kpa) Sensitivity, S t Peak Remolded 5 Depth (meters) Depth (meters) VST Results courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 141 of 235 VANE SHEAR TEST (VST) (ASTM D ) Table 11-7 Typical Values of Sensitivity Condition Range of S t U.S. Sweden Low sensitive 2 4 < 10 Med. sensitive Highly sensitive 8 16 > 30 Quick 16 > 50 Extra quick - > 100 Greased lightening - (figure and table from: Holtz, RD, and Kovacs, WD (1981) An Introduction to Geotechnical Engineering, Prentice-Hall, New Jersey) Fig. 2.9 (a) Undisturbed and (b) thoroughly remolded sample of Leda clay from Ottawa, Ontario. (Photograph courtesy of the Division of Building Research National Research Council of Canada. Hand by D.C. MacMilan) VST Results courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 142 of

72 CONE PENETRATION TEST (CPT) (ASTM D ) Electronic Steel Probes with 60 Apex Tip Hydraulic Push at 20 mm/s No Boring, No Samples, No Cuttings, No Spoil Continuous readings of stress, friction, pressure With Pore Pressure Measurements (CPTu) With Shear Wave Measurements (SCPT) Text and Figures courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 143 of 235 CONE PENETRATION TEST (CPT) RIGS Figures courtesy of FHWA NHI Course Subsurface Investigations & WPC Engineering Inc Drilled Deep Foundations Samuel Paikowsky 144 of

73 CONE PENETRATION TESTING (CPT) Factors Affecting CPT Results Figure 9-2. FHWA NHI Course Subsurface Investigations V s f s U 2 q c Drilled Deep Foundations Samuel Paikowsky 145 of 235 CPT Cone Penetration Test General (ASTM D ) Deep, Quasi-Static, Cone and Friction-Cone Penetration Tests of Soils. The CPT is an in-situ, sounding method in which a cone (usually 60 o and 10 cm 2 base area) is pushed into the ground at a rate of approximately 10 to 20 mm/sec and the resistance to penetration is measured. Useful in soft clays and fine to medium coarse sands. It encountered difficulties in stiff/hard, cemented or highly over-consolidated soils. Advantage - obtaining considerable information in a short time. Disadvantage - non-recoverability of samples and the above difficulties Drilled Deep Foundations Samuel Paikowsky 146 of

74 CPT Cone Penetration Test Figure 2.24 Electric Friction-cone penetrometer (after ASTM, 2001) Drilled Deep Foundations Samuel Paikowsky 147 of 235 CONE PENETRATION TEST (CPT) (ASTM D ) V s Shear Wave Velocity (V s ) f s Sleeve Friction (f s ) u 2 Penetration Porewater Pressure (U 2 ) q c Cone Tip Resistance (q c ) Figures courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 148 of

75 Corrections to CPT Measurements (with U 2 ) Need to correct tip resistance (q c ) for pore U2 location. q c q t U 2 = U b Pore Pressure Measurement behind Tip Porous Element for U 2 Materials: Sintered Metals, Ceramics, Plastics (disposable) Saturation of Porous Elements: Water, Glycerine, Silicone Procedures: Vacuum for 24-hours, Pre-Saturated Elements, Prophylactic to maintain fluids Courtesy of FHWA IF Drilled Deep Foundations Samuel Paikowsky 149 of 235 Obtained Data cone-tip resistance q c CPT Cone Penetration Test sleeve friction resistance f s piezocone allows pore pressure readings, usually at the tip (u 1 ) also possible at the base (u 2 ) and above friction sleeve (u 3 ). f R = F R = Friction ratio = f s /q c x 100% u 3 u 2 u Drilled Deep Foundations Samuel Paikowsky 150 of

76 U2 Cone No: 3318 Tip area [cm2]: 10 Sleeve area [cm2]: 150 1/31/2014 CPT Cone Penetration Test Drilled Deep Foundations Samuel Paikowsky 151 of 235 CONE PENETRATION TESTING (CPT) RESULTS Soil Profile q c f s u o, u 2 F R qt [tsf] fs [tsf ] u2 [tsf] R f [%] U o [tsf] Very stiff fine grained (9) C layey silt to silty clay (4) Clays, clay to silty clay (3) C layey silt to silty clay (4) Silty sand to sandy silt (5) 20 Silty sand to sandy silt (5) Clays, clay to silty clay (3) 24 Clays, clay to silty clay (3) Silty sand to sandy silt (5) 28 C layey silt to silty clay (4) Clays, clay to silty clay (3) Silty sand to sandy silt (5) Clean sands to silty sands (6) Silty sand to sandy silt (5) Clays, clay to silty clay (3) C layey silt to silty clay (4) Depth [ft] Te st no: B-06 Client: Pro ject: Po sition: X: m, Y: m Project in Savannah, GA SAV Ground level: Date: Scale: 2/11/2002 Page: Fig: 1 File: sav sc6.cpd CPT Results courtesy of Dr. Edward Hajduk and WPC Engineering Inc Drilled Deep Foundations Samuel Paikowsky 152 of

77 Data Interpretation CPT Cone Penetration Test Use of data can be applied directly in design using the similarity between the cone and a pile or with correlation to soil parameters Soil Identification A major drawback of the cone is the inability of obtaining actual soil sample. As such correlation based on the relationship between the friction ratio and soil type has been developed. Soil identification becomes easier with the piezocone which uses pore water pressure besides the friction ratio Drilled Deep Foundations Samuel Paikowsky 153 of 235 CPT Cone Penetration Test Soil classification chart for standard electric cone. Use with caution and/or together with recovered tube samples [After Robertson and Campanella(1983)], see Figure 2.31, p Drilled Deep Foundations Samuel Paikowsky 154 of

78 CONE PENETRATION TEST (CPT) DETERMINATION OF SOIL STRATIGRAPHY CPT Soil Behavior Classification (Based on q t, FR or B q ) Figure 9-3. FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 155 of 235 CONE PENETRATION TEST (CPT) DETERMINATION OF SOIL STRATIGRAPHY Drilled Deep Foundations Samuel Paikowsky 156 of

79 EXAMPLE INTERPRETATION CPT Given Data Soil Profile q t (tsf) f s (tsf) U o, U 2 (tsf) FR Depth (ft) Drilled Deep Foundations Samuel Paikowsky 157 of 235 EXAMPLE INTERPRETATION CPT Soil Layers Soil Profile q t (tsf) f s (tsf) U o, U 2 (tsf) FR 7ft Depth (ft) SAND 9ft SANDY SILT 17ft SILTY CLAY (MARL) Drilled Deep Foundations Samuel Paikowsky 158 of

80 Cohesive Soils CPT Cone Penetration Test Cone bearing resistance q c correlated to undrained shear strength Su = Cu. Using ultimate bearing strength as for foundation - pile tip in clay. q c = q p + vo q c = cone-tip resistance q p = point resistance vo = total vertical pressure in the soil at tip elevation q p = C u N c or S u N k in which N c = N k = Bearing Capacity Factor or Cone Factor in this case. q c = S u N k + vo q c = C u N c + vo C u = (eq. 2.51, p. 105) Drilled Deep Foundations Samuel Paikowsky 159 of 235 CPT Cone Penetration Test Cohesive Soils (cont d.) Analogous to Poulus et al. (2003) N k = 17.2 (electronic cone), N k = 18.9 (mechanical cone) N k = N c = use N c = % (N k is based on Pent. Testing. Proc. Of 2nd European Symp. On Penet. Testing /ESPOT II. Amsterdam. 1982). Using Mayne and Kemper (1988) (see eq. 2.55, p.107) OCR = Drilled Deep Foundations Samuel Paikowsky 160 of

81 CPT Cone Penetration Test Granular Soils (text pp ) D R = f (q c, v, A, B) Use equation 2.44 with A = -98, B = 66 Use Figure below for D R = f (q c, v ) See alternatively Figure 2.29 for v, q c and D R correlations based on Baldi et al., 1982, and Robertson & Campanella, Drilled Deep Foundations Samuel Paikowsky 161 of 235 CPT Cone Penetration Test Granular Soils (cont d.) Internal Friction Angle from CPT Kalhawy and Mayne (1990) based on Robertson and Campanella (1985) tan 1 q c log 0 (eq. 2.47, see figure) Variation of q c with 0 and in normally consolidated quartz sand (after Robertson and Campanella, 1983) Drilled Deep Foundations Samuel Paikowsky 162 of

82 Depth (ft) EXAMPLE INTERPRETATION CPT Determination of q t,ave, t, and ' vo SAND - Silty SAND q t,ave 125 tsf use t = 115 pcf Sandy SILT q t,ave 22 tsf use t = 110 pcf Depth (ft) Silty CLAY - CLAY q t,ave 26 tsf use t = 115 pcf C-7 q t (tsf) ' vo (psf) t from Table Soil Engineering Properties Correlations (pg. 69 of notes) Drilled Deep Foundations Samuel Paikowsky 163 of 235 Depth (ft) EXAMPLE INTERPRETATION CPT Determination of Effective Friction Angle ( ') SAND - Silty SAND q t,ave 125 tsf use t = 115 pcf Sandy SILT q t,ave 22 tsf use t = 110 pcf Silty CLAY - CLAY q t,ave 26 tsf use t = 115 pcf C-7 q t (tsf) Calculate q t,ave for sand layer from 0 to 7 ft Simple Way: Using Table Soil Engineering Properties Correlations (pg. 69 of notes) q t,ave 125 tsf 12 MPa therefore ' 37 Formula Way: Using Robertson and Campanella (1983) formula. ' = arctan[ log(q t / ' vo )] Use q t,ave 12 MPa ( psf) & ' vo,ave = 405 psf for layer. Using equation, ' = 49 USE ' Drilled Deep Foundations Samuel Paikowsky 164 of

83 Depth (ft) EXAMPLE INTERPRETATION CPT Determination of Undrained Shear Strength (S u ) SAND - Silty SAND q t,ave 125 tsf use t = 115 pcf Sandy SILT q t,ave 22 tsf use t = 110 pcf Silty CLAY - CLAY q t,ave 26 tsf use t = 115 pcf C-7 q t (tsf) Calculate q t,ave for Sandy Silt from 7 to 17 ft Calculate q t,ave for Silty Clay from 17 to 24 ft Formula Way: use Aas et al. (1986) S u = (q t - vo )/N kt N kt = 15 for CHS (Lecture Slides) Sandy SILT Layer Use q t,ave 22 tsf & vo,ave = 1355 psf S u = 2850 psf Silty CLAY Layer Use q t,ave 26 tsf & vo,ave = 2310 psf S u = 3300 psf Drilled Deep Foundations Samuel Paikowsky 165 of 235 CPT Cone Penetration Test Correlation between SPT to q c This relation is Important as many correlations exist between N SPT and different soil parameters and they can be utilized with the transformation from q c to N Figure 2.30 General range of variation of q c /N 60 for various types of soil (after Robertson and Campanella, 1983) Drilled Deep Foundations Samuel Paikowsky 166 of

84 CPT Cone Penetration Test Correlation between SPT to q c (cont d.) Eq qc p N 60 a D D 50 (mm); q c same units as p a Drilled Deep Foundations Samuel Paikowsky 167 of 235 Depth (ft) EXAMPLE INTERPRETATION SPT & CPT Comparison of Soil Engineering Properties SPT SAND - Silty SAND N ave = 17 use t = 115 pcf Sandy SILT N ave = 4 use t = 110 pcf Clayey SILT (MH)/MARL N ave = 4 use t = 115 pcf Depth (ft) B-7 N (bpf) Two Tests ~ 15 ft Apart CPT SAND - Silty SAND q t,ave 125 tsf use t = 115 pcf Sandy SILT q t,ave 22 tsf use t = 110 pcf Silty CLAY - CLAY q t,ave 26 tsf use t = 115 pcf C-7 q t (tsf) Sand Layer Properties Method SPT - Table Soil Engineering Properties Correlations (pg. 69 of notes) Drilled Deep Foundations Samuel Paikowsky 168 of 235 t (pcf) ' ( ) SPT - Formula NA 44 CPT - Table Soil Engineering Properties Correlations (pg. 69 of notes) CPT - Formula NA 49 84

85 ROCK EXPLORATION Geophysical Methods Geologic Mapping (need qualified geologists) Drilling and Coring Exploration Test Pits UML Health and Social Sciences Building Lowell, MA June 14, 2011 (picture courtesy of Dr. Edward Hajduk) Drilled Deep Foundations Samuel Paikowsky 169 of 235 ROCK EXPLORATION Drilling and Coring Rock Coring (see text section 2.24) Rock cores are necessary to establish the soundness of the rock. Using a coring bit at the bottom of the core barrel. Water is used for washing the rock dust out and cooling the drilling. STB Refusal Auger refusal SPT refusal (> 50 blows per 1 inch penetration) Coring (ASTM D2113) Noncore Drilling Percussive Methods ASTM D Standard Practice for Rock Core Drilling and Sampling of Rock for Site Investigation Drilled Deep Foundations Samuel Paikowsky 170 of

86 ROCK EXPLORATION Drilling Rotary Wash Drill Rig Tricone, Roller, Plug Bits Figures courtesy of FHWA NHI Course Subsurface Investigations Roller Bits Drilled Deep Foundations Samuel Paikowsky 171 of 235 ROCK EXPLORATION Coring Diamond Bits. Best and hardest, producing high quality core. Fastest cutting rates. Expensive. Synthetic Bits. Less expensive. Generally good quality cores. Tungsten Carbide Bits. Least expensive. Slower coring rates. Diamond Diamond, Carbide Tungsten, Sawtooth Carbide Type Bits Photograph courtesy of Drilled Deep Foundations Samuel Paikowsky 172 of

87 Most rugged, least expensive. Consists of head section, core recovery tube, reamer shell, & cutting bit. Often used as starter when beginning core operations ROCK EXPLORATION Coring Single Tube Core Text & Figures courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 173 of 235 Rock Coring (cont d.) Double tube core barrel and core bit greater than AWT (core>1 1 / 8 ) reduces the breakage inside the drill barrel (too large is not good either). Using recovery ratio and RQD as measures of quality (see eqs. 2.70, 2.71 on p. 117). Using unconfined and high-pressure triaxial tests on the recovered samples (note: provides strength and deformation of the sound rock only, not the rock mass). Recovery Ratio = Length of rock recovered Theoretical length of rock recovered Drilled Deep Foundations Samuel Paikowsky 174 of

88 Rock Coring (cont d.) Figure 2.38 Rock coring: (a) single-tube core barrel; (b) double-tube core barrel RQD = Rock Quality Designation = L of recovered pieces 4" size Theoretical length of rock cored Drilled Deep Foundations Samuel Paikowsky Inner Barrel Assembly Outer Barrel Assembly ROCK EXPLORATION Coring Double Tube Core Double tube core barrel is the standard. Outer barrel rotates with cutting bit. Inner barrel is either fixed or swivel type (with bearings) that retains core sample. Core diameters generally range from 21 to 85 mm (0.85 to 3.35 inch). NX core: standard diameter = 54 mm (2.15 inches). ASTM C42: The diameter of cores for determining f c in load bearing structural members shall be at least 3.70 in. Text & Figures courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 176 of

89 ROCK EXPLORATION Coring Triple Tube Core Text & Figures courtesy of FHWA NHI Course Subsurface Investigations Good for obtaining core samples in fractured rock and highly weathered rocks. Outer core barrel for initial cut and second barrel to cut finer size. Third barrel to retain cored samples. Reduces frictional heat that may damage samples Drilled Deep Foundations Samuel Paikowsky 177 of 235 ROCK EXPLORATION Coring Drilling Fluids Notes Rotary wash with water, foam, or drilling mud (bentonitic or polymeric slurries). Fluids reduce wear on drilling and coring bits by cooling. Fluids remove cuttings & rock flour. Re-circulate to filter fluids and to minimize impact on environment Text & Figures courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 178 of

90 Stabilizes boreholes Driven casing Drilled-in casing Dual wall reverse circulation method Use in areas with expected large losses in drilling fluid Inner section for sampling Outer casing maintains fluids for drilling ROCK EXPLORATION Coring Casing Drilled-In Text & Figures courtesy of FHWA NHI Course Subsurface Investigations Dual Wall Drilled Deep Foundations Samuel Paikowsky 179 of 235 ROCK EXPLORATION Core Recovery Core Runs taken in either 5- or 10-foot sections. Log the amount of material recovered. Core Recovery is percentage retained. RQD (Rock Quality Designation) is a modified core recovery. ASTM D5079 Standard Practice for Preserving and Transporting Rock Core Samples Figures courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 180 of

91 ROCK EXPLORATION Core Recovery Cores should be stored in either wooden boxes or corrugated cardboard box. Box marked with boring number, depth of core run, type core, bit type, core recovery (CR), rock type, RQD, and other notes. Core operations should be documented: Loss of fluid Drilling rates Sudden drop in rods Poor recovery Loss of core Text & Figures courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 181 of 235 ROCK EXPLORATION Core Recovery The RQD is a modified core recovery. Measure of the degree of fractures, joints, and discontinuities of rock mass RQD = sum of pieces > 100 mm (4 inches) divided by total core run. Generally performed on NX-size core. Text & Figures courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 182 of

92 Routine: Core boxes Special: Plastic sleeves General: Avoid exposure to shock and vibration during handling and transport. Non-natural fractures may result from excessive movements, temperatures, and exposure to air. Store for future reference ROCK EXPLORATION Care & Preservation Text & Figures courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 183 of 235 Groundwater Measurements Observation of groundwater elevation using an observation well. Allows the monitoring of groundwater levels with time and for environmental tracking purposes. Initial readings need to be taken after groundwater stabilization is obtained, at least 24 hours after the end of drilling (in low permeability soils may require much longer time) Drilled Deep Foundations Samuel Paikowsky 184 of

93 Piezometers (Guide to Geotechnical Instrumentation, SLOPE INDICATOR, 2004) Drilled Deep Foundations Samuel Paikowsky Example of Vibrating Wire Piezometers Manufactured by Geokon, Inc Drilled Deep Foundations Samuel Paikowsky 186 of

94 Groundwater Measurements (cont d.) Local Water Pressure can be measured utilizing a piezometer. Such readings are necessary in low permeability soils, which exhibit variation of pressure with time, e.g.: following pile driving, surcharge application (to establish the progress of consolidation) or for artesian or separated acquifers. Piezometer can be pushed into the ground as a self contained unit or installed in a borehole Drilled Deep Foundations Samuel Paikowsky 187 of 235 Piezometers (Guide to Geotechnical Instrumentation, SLOPE INDICATOR, 2004) Drilled Deep Foundations Samuel Paikowsky 94

95 Geophysical Explorations Wave Types: Three major wave types propagate through the soil upon impact or vibration; Rayleigh Waves = surface Waves P-waves = pressure or plane wave S-waves = shear waves Being interested in waves propagating and reflecting from various soil layers, P-waves are the fastest penetrating waves, and therefore of interest Drilled Deep Foundations Samuel Paikowsky 189 of 235 Geophysical Explorations Wave Types: Three major wave types propagate through the soil upon impact or vibration; Rayleigh Waves = surface Waves P-waves = pressure or plane wave S-waves = shear waves Being interested in waves propagating and reflecting from various soil layers, P-waves are the fastest penetrating waves, and therefore of interest Drilled Deep Foundations Samuel Paikowsky 190 of

96 Geophysical Explorations Wave Types: (cont d) Pressure Wave P Direction of Travel Shear Waves S Direction Of Travel Drilled Deep Foundations Samuel Paikowsky 191 of 235 GEOPHYSICAL METHODS MECHANICAL WAVES Seismic Refraction (SR) (courtesy of Also Available: Downhole Tests (DHT) Spectral Analysis of Surface Waves (SASW) Crosshole Tests (CHT) (FHWA NHI Figurer 5-25) Drilled Deep Foundations Samuel Paikowsky 192 of

97 Geophysical Explorations Seismic Refraction survey: Section 2.26 (p. 118) describes the ability to identify the variation in the layers and the subsurface based on wave velocity and time measurements utilizing impact (point A) and geophones at the ground surface at known locations (B, C, D) Drilled Deep Foundations Samuel Paikowsky 193 of 235 Geophysical Explorations Seismic Refraction survey: (cont d.) 1. The first arrival at locations B, C, D is measured as t 1, t 2, t 3, etc. 2. Plotting the time vs. the distance from the source enables to identify zones of different slopes reflecting the various velocities. Slope of Slope of Slope of 1 ab v1 1 bc v2 1 cd v Here, v 1, v 2, v 3,, are the P-wave velocities in layers I, II, III,, respectively 3 Figure 2.42 Seismic refraction survey Drilled Deep Foundations Samuel Paikowsky 194 of

98 Geophysical Explorations Seismic Refraction survey: (cont d.) 3. Determine the Thickness of the top Layer: Z v2 v v v 1 x c 1 (eq. 2.73, p.120) The value of xc can be obtained from the plot, as shown in Figure 2.31b (p. 107). 4. Determine the Thickness of the Second Layer: 1 Z 2 2 Ti 2 2Z v3 v 1 v3v1 v v v v2 (eq. 2.74, p.120) Here T i2 is the time intercept of the line cd in Fig. 2.42b, (p.119) extended backwards Drilled Deep Foundations Samuel Paikowsky 195 of 235 Geophysical Explorations Seismic Refraction survey: (cont d.) Findings: The velocities of P waves in various layers indicate the types of soil or rock that are present below the ground surface. The range of the P- wave velocity that is generally encountered in different types of soil and rock at shallow depths is given in Table Drilled Foundation Deep & Foundations Soil Engineering Samuel Samuel Paikowsky Paikowsky 196 of

99 Geophysical Explorations Seismic Refraction survey: (cont d.) Applications and Limitations 1. The survey enables to cover large areas in a short time at a relatively low cost. 2. The conditions at the site need to be adequate, namely: relatively uniform, deep ground water surface, P-wave velocity v 1 <v 2 <v 3 3. In saturated soils/fractured rock the P-wave velocity often resumes that of water ( 1500m/s) 4. Verification with actual drilling is needed Drilled Deep Foundations Samuel Paikowsky 197 of 235 GEOPHYSICAL METHODS ELECTROMAGNETIC WAVES Electrical Resistivity (ER) Survey Results (FHWA NHI Figurer 5-35) Electromagnetic (EM) Survey (FHWA NHI Figurer 5-35) Ground Penetrating Radar (GPR) (photographs courtesy of Other Methods: Magnetometer Surveys (MS) Resistivity Piezocone (RCPTu) Drilled Deep Foundations Samuel Paikowsky 198 of

100 GEOPHYSICAL METHODS ADVANTAGES OF GEOPHYSICS Nondestructive and/or non-invasive Fast and economical testing Theoretical basis for interpretation Applicable to soils and rocks MS Results for Oil Well Location (FHWA NHI Figure 5-37) GPR Results for UST (FHWA NHI Figure 5-33) DISADVANTAGES OF GEOPHYSICS No samples or direct physical penetration Models assumed for interpretation Affected by cemented layers or inclusions. Results influenced by water, clay, & depth Drilled Deep Foundations Samuel Paikowsky 199 of 235 INSITU TESTING METHODS Figure courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 200 of

101 INSITU TEST METHOD ADVANTAGES/DISADVANTAGES Method Advantages Disadvantages VST Assessment of undrained shear strength of clays. Simple test and equipment. Measure inplace sensitivity. Long history of use in practice, particularly embankments, foundations, & cuts. Limited to soft to stiff clays & silts with s uv < 200 kpa Slow & time-consuming Raw s uv needs empirical correction Can be affected by sand seams and lenses Drilled Deep Foundations Samuel Paikowsky 201 of 235 INSITU TEST METHOD ADVANTAGES/DISADVANTAGES Method Advantages Disadvantages DCP SPT Quick Low cost Obtain Sample + Number Simple & rugged device at low cost Suitable in many soil types Can perform in weak rocks Available throughout the U.S. and worldwide. Many correlations with soil engineering properties exist Limited depth range Limited correlations of DCP values to soil properties. Obtain Sample + Number Disturbed sample (index tests only) Crude number for analysis Not applicable in soft clays and silts High variability and uncertainty Many correlations with soil engineering properties exist Drilled Deep Foundations Samuel Paikowsky 202 of

102 INSITU TEST METHOD ADVANTAGES/DISADVANTAGES Method Advantages Disadvantages CPT DMT Fast and continuous profiling of strata. Economical and productive. Results not operator-dependent. Strong theoretical basis for interpretation. Particularly suited to soft soils. Simple and Robust Equipment. Repeatable and Operator- Independent. Quick and Economical. Theoretical Derivations for elastic modulus, strength, stress history. High capital investment Requires skilled operator for field use. Electronics must be calibrated & protected. No soil samples. Unsuited to gravelly soils and cobbles. Difficult to push in dense and hard materials. Primarily established on correlative relationships. Needs calibration for local geologies Drilled Deep Foundations Samuel Paikowsky 203 of 235 FLAT PLATE DILATOMETER (DMT) (ASTM D (2007)) Figure courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 204 of

103 FLAT PLATE DILATOMETER (DMT) (ASTM D (2007)) Calibrations: A, B (positive values) Readings: contact pressure "A" and expansion pressure "B" with depth Corrections for membrane stiffness in air: p 0 = 1.05(A + A) (B - B) p 1 =B - B DMT INDICES: I D = material index = (p 1 -p o )/(p o -u o ) E D = dilatometer modulus = 34.7(p 1 -p o ) K D = horizontal stress index = (p o -u o )/ vo Text courtesy of FHWA NHI Course Subsurface Investigations A B Drilled Deep Foundations Samuel Paikowsky 205 of 235 FLAT PLATE DILATOMETER (DMT) (ASTM D (2007)) Manual Reading System (Standard) Marchetti Device (ASCE JGE, March 1980; ASTM Geot. Testing J., June 1986) Figures courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 206 of

104 FLAT PLATE DILATOMETER (DMT) (ASTM D (2007)) Computerized System (Standard) Figure courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 207 of 235 FLAT PLATE DILATOMETER DETERMINATION OF SUBSURFACE DATA Material Index, I D p1 p p u Clay Silt Sand Material Index (I D ) p 0 p 1 Courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 208 of

105 FLAT PLATE DILATOMETER DETERMINATION OF SUBSURFACE DATA Figure 43. FHWA IF Drilled Deep Foundations Samuel Paikowsky 209 of 235 FLAT PLATE DILATOMETER (DMT) (ASTM D (2007)) Results Charleston, SC Project Soil Behavior Classification E D with Depth Raw Data & Calibrations DMT Results courtesy of Dr. Edward Hajduk and WPC Engineering Inc Drilled Deep Foundations Samuel Paikowsky 210 of

106 FLAT PLATE DILATOMETER (DMT) (ASTM D (2007)) Results - Piedmont Residuum, Charlotte, NC Depth (meters) Po P1 14 Clay Silt Pressure (kpa) Material Index I D Modulus E D (atm) DMT Results courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 211 of Horiz. Index K D SPT-CPT-DMT COMPARISON From Local Project in Charleston, SC Area (2000) Also see Hajduk, E.L., Meng, J., Wright, W.B., and Zur, K.J. (2006). Dilatometer Experience in the Charleston, South Carolina Region, 2nd International Conference on the Flat Dilatometer, Washington, D.C Drilled Deep Foundations Samuel Paikowsky 212 of

107 PRESSUREMETER TEST (PMT) (ASTM D ) Figure courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 213 of 235 PRESSUREMETER (PMT) (ASTM D ) Results Utah DOT Project Pressure (tsf) 3 2 Pressure (tsf) Volume Change (cc) Creep (cc/min) PMT Results courtesy of FHWA NHI Course Subsurface Investigations Drilled Deep Foundations Samuel Paikowsky 214 of

108 NE Subsurface Combining NE Geology and Subsurface Explorations Agenda Rock Core Viewing (next lecture) New England Surficial Geology Overview Typical Soil Types Typical Soil Stratigraphic Sequences Examples of Applied Subsurface Evaluation Drilled Deep Foundations Samuel Paikowsky 216 of

109 Rock Coring Drilled Deep Foundations Samuel Paikowsky 217 of 235 Rock Coring RQD = Rock Quality Designation RQD = Σpieces >10cm x 100 Total Core run RQD Rock mass quality <25% very poor 25-50% poor 50-75% fair 75-90% good % excellent Drilled Deep Foundations Samuel Paikowsky 218 of

110 Direct Push Soil Sampling Drilled Deep Foundations Samuel Paikowsky 219 of 235 More Direct Push Drilled Deep Foundations Samuel Paikowsky 220 of

111 Sonic Drilling Sample Recovery Drilled Deep Foundations Samuel Paikowsky 221 of 235 Split Spoon Sampler Drilled Deep Foundations Samuel Paikowsky 222 of

112 Glacial Stratigraphy Concord, MA Drilled Deep Foundations Samuel Paikowsky 223 of 235 Glacial Stratigraphy Concord, MA (2) Drilled Deep Foundations Samuel Paikowsky 224 of

113 Glacial Stratigraphy Glastonbury, CT Drilled Deep Foundations Samuel Paikowsky 225 of 235 Glacial Stratigraphy Everett, MA Drilled Deep Foundations Samuel Paikowsky 226 of

114 Glacial Stratigraphy- Cape Cod, the Mass Military Reservation Pew Rd. Frank Perkins Rd. clay lens? 2x longer than RDX plume Plume shallows beyond FPR Evidence of a hydraulically significant confining layer current RDX extent center of mass trajectory Drilled Deep Foundations Samuel Paikowsky 227 of 235 Glacial Stratigraphy- Western MA Drilled Deep Foundations Samuel Paikowsky 228 of

115 Glacial Stratigraphy - Maine Stratified Drift till bedrock Drilled Deep Foundations Samuel Paikowsky 229 of 235 Glacial Stratigraphy Midwest Schematic Drilled Deep Foundations Samuel Paikowsky 230 of

116 Central Artery Stratigraphy Organic Silt Fill Boston Blue Clay Till Bedrock (Argillite) Drilled Deep Foundations Samuel Paikowsky 231 of 235 Boston- The Central Artery Drilled Deep Foundations Samuel Paikowsky 232 of

117 Boston- Central Artery Dewatering Model Results Drilled Deep Foundations Samuel Paikowsky 233 of 235 Hydraulic Conductivity Ranges Drilled Deep Foundations Samuel Paikowsky 234 of

118 Engineering Characteristics of Glacial Deposits Drilled Deep Foundations Samuel Paikowsky 235 of