Instructional Objectives

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1 GE 343 SUBSURFACE EXPLORATION CH 6 Drilling in Overburden Text Ch. 7. Dr. Norbert H. Maerz Missouri University of Science and Technology (573) norbert@mst.edu Instructional Objectives 1. List the rules of thumb for boring spacing and depths. 2. Explain the requirements for locating underground services before you dig. 3. Select and justify a drilling method for a given design use and geological scenario. 4. Select and justify a sampling method and strategy for a given design use and geological scenario. 5. Select and justify an insitu testing method and strategy for a given design use and geological scenario. 1

2 Exploration Program Evaluate the variety of methods and procedures available Depends on the type of construction and the geological conditions encountered Exploration Plan 1. Key locations to clarify the geological interpretation as a whole. 2. Key location that could lead to relocation or redesign. 3. Bridges or other structures. 4. Deep cuts and high embankments. 5. Areas of engineering difficulty or complicated ground surface. 6. Off-line investigations for geological hazards or borrow surveys. 2

3 Exploration Plan 7. Points of Interpolation (function of complexity of the geology). 8. Least expensive methods of investigation should be used first. These may provide sufficient information by themselves, or will indicate where more detailed and expensive investigations may be required. 9. In areas of intense, complex, or expensive construction activity, it may be necessary to conduct very sophisticated and expensive which include horizontal boring, inspection shafts or pilot tunnels. Types of Borings 1. Pilot borings 2. Control borings 3. Verification borings 3

4 Exploration Spacing 1. Narrow right of ways 150 m 2. Uniform conditions for subgrade m, up to 300 m in the Midwest 3. With increasing complexity m 4. Highly erratic critical foundations 8-15 m 5. High embankments and deep cuts 60 m, in compressible materials 30 m 6. Specific structure borings, 30 m or at each end of the structure Exploration Spacing 7. Critical Areas (irregular bedrock, bogs, caverns 15 m grid 8. Tunnels: soft ground adverse conditions m, favorable conditions m 9. Tunnels: mixed-face adverse conditions 8-15 m, favorable conditions m 10.Tunnels: hard ground adverse conditions m, favorable conditions m 4

5 Exploration Depths 1. Subgrade borings 2-3 meters below profile elevation 2. High embankments, 2-4 times the height of the embankment 3. Excavations > 5 m, 2 times depth 4. Specific structure borings- to depth of where net increase in soil stress due to structural load is less than 10 of effective stress. Minimum 10 m below footing (3 m into rock) Exploration Depths 5. Critical Areas deep enough to evaluate their extent 6. Tunnel borings: 1 to 1.5 time tunnel diameter below grade. If alignment is subject to modifications, then 2 to 3 times 5

6 Sampling Requirements Every change in soil strata At interval not to exceed 1.5 m Rock core continuously Right of Way, Permits, Utilities Permission from property owners, preferably written Formalized permits for certain access Underground utilities Overhead utilities 6

7 1-800-Dig-Rite /excavmanual.pdf 7

Color codes http://mo1call.com/codes_index.

8 Color codes Soil Drilling Methods Displacement boring Wash boring Percussive drilling (rock) Rotary drilling (rock) Auger boring Sonic Drilling 8

Displacement Boring Method where a piston or plug-type sampler is forced into the soil to the desired depth, displacing all the material on its path.

9 Displacement Boring Method where a piston or plug-type sampler is forced into the soil to the desired depth, displacing all the material on its path. Upon reaching the desired depth, the sampler is retracted and "grabs' a sample on its way back to the surface. PROS: Does not require heavy equipment (by hand or lightweight equipment); Clean method for shallow well installation; CONS: Method limited to shallow depths; Method limited to soft soils and boulder, cobble-free zones; Not efficient if necessary to install several wells; Practical limitation up to ~ 2" diameter sampler. Similar to the above method is "Direct Push Technology" or DPT. A common trade name is GeoProbe. DPT does not require heavy equipment, most units are pickup mounted or ATV mounted for easy accessibility. Wash Borings 9

10 Continuous Flight Augers Construction Augers Solid stem Hollow stem Truck mounted Track mounted Construction Auger 10

11 Solid Stem Continuous Flight Augers FHWA NHI

Solid-stem auger Method consists of drilling a continuous helix into the ground. The torque is provided by a top drive auger drilling machine, which permits both downward push and retraction.

12 Solid-stem auger Method consists of drilling a continuous helix into the ground. The torque is provided by a top drive auger drilling machine, which permits both downward push and retraction. Individual flights are normally 5 feet long. Different drill bits can be attached to the bottom of the auger to meet the formation requirement, which cut a hole ~10 % greater in diameter than the diameter of the auger. PROS: Rapid and low-cost drilling in clayey formations; Clean method, does not require circulation fluids; No casing necessary where the formation is stable; Allows collection of representative sample in semi-consolidated formations; CONS: Practical limitation to 24" diameter; Inefficient in loose, sandy material (depends on the depth); Inefficient below the water table (depends on the depth). Hollow Stem Continuous Flight Augers FHWA NHI

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Hollow-stem auger This is a form of continuous-flight auger where the helices are wound around and welded to a tubular center stem or axle. Drilling proceeds essentially as in solid-stem drilling.

installation can be performed. Other drilling methods can also proceed within the hollow stem, which can be used as temporary casing to prevent caving.

14 Hollow-stem auger This is a form of continuous-flight auger where the helices are wound around and welded to a tubular center stem or axle. Drilling proceeds essentially as in solid-stem drilling. When the sections are connected however, the hollow-stem auger will present a smooth, uniform bore throughout its length thus providing an open, cased hole in which samplers can be used or well installation can be performed. Other drilling methods can also proceed within the hollow stem, which can be used as temporary casing to prevent caving. PROS: Allows collection of uncontaminated sample in unconsolidated formation; Can be used as temporary casing to prevent caving; Relatively rapid, especially in clayey formations; CONS: Ineffective through boulders; Limited drilling in loose, granular soils, particularly below the water table where sample recovery can be compromised; Difficult to retrieve a sample in loose, granular soil because cuttings don't always want to come to the surface. Samples must be collected with a split spoon or a continuous corer, either of which can provide excellent samples if done correctly; Limited to rather shallow depths. Hollow stem auger drilling 14

15 Hollow stem auger drilling Rotary Wash Boring FHWA NHI

borehole walls and the pipe string. The penetration rate is often faster and the bit life longer when using air as compared with water based drilling fluids.

16 Rotary Wash Boring This method makes use of a constantly rotating bit to penetrate any type of formation to depths that can exceed 1,000 feet. As drilling proceeds, cuttings are removed by a continuous circulation of fluid (either air or water based) that flows down inside the pipe string and up-hole along the annular space between the borehole walls and the pipe string. The penetration rate is often faster and the bit life longer when using air as compared with water based drilling fluids. A drag bit is normally used to penetrate unconsolidated to semi-consolidated sediments; while a conetype or roller bit is used to drill consolidated rock. PROS: High penetration rate; Drilling operation requires a minimum amount of casing; Rapid mobilization and demobilization; CONS: Use of a drilling fluid, both in terms of sample contamination and water management (in the case of water-based fluids and air injected by gasoline compressors); Circulation of drilling fluid may be lost in loose/coarse formations, hence making difficult to transport drill cuttings; Difficult to collect accurate samples, i.e. a sample from a discrete zone since the cuttings accumulate at surface around the rim of the borehole. MODOT Rig 16

Sonic Drilling Faster speed (2-3x) Better core

com/what_we_do/pdf/sonic_drilling_methodology.

17 Sonic Drilling Faster speed (2-3x) Better core recovery Less waste (70-80%) Up to 12 core Up to 500 deep No drilling mud Less collapse problems Boart Longyear rig 17

18 Rotosonic Video 18

19 Home Depot Other Tools Test pits (backhoe, bulldozer) Hand dug test pits Hand Augers Portable powered auger Franklin Horizontal Drilling Horizontal drilling in rock Horizontal drains and tiebacks Ditch Witch Coil tubing drilling 19

20 Ditch Witch Coil Tubing Drilling 20

21 Drilling Fluids/Stabiliztion Water stabilization Drilling mud Air stabilization Casing stabilization Grout stabilization Freezing Stabilization Soil Sampling Disturbed Samples Wash sampling Auger cuttings Bulk Modified California Split spoon Undisturbed Samples Thin walled sampling tube (Shelby Tube) Piston sampler Bishop sand sampler Continuous push (Geoprobe) Pitcher Denison Block Core barrel (rock) 21

22 Undisturbed Sampling ASCE FHWA NHI

23 Split Spoon FHWA NHI

24 Thin Walled Samplers/Shelby Tube FHWA NHI Sampling tools inside augers 24

25 Piston Samplers FHWA NHI Osterberg sampler 25

26 Mechanical Stationary Piston Sampler Retractable Piston Sampler 26

27 Hydraulic Piston Sampler Bishop Sand Sampler 27

28 Pitcher Tube FHWA NHI Pitcher Tube Sampler 28

29 Insitu Tests in Soil FHWA NHI Standard Penetration Test (STP) FHWA NHI

30 Standard Penetration Test (STP) Driven by a 140 lb hammer dropping 30, multiple blows (counts) = standard penetration test Standard Penetration Test (STP) ADVANTAGES DISADVANTAGES Obtain both a sample & a number Simple & Rugged Suitable in many soil types Can perform in weak rocks Available throughout the U.S. Obtain both a sample & a number * Disturbed sample (index tests only) Crude number for analysis Not applicable in soft clays & silts High variability and uncertainty FHWA NHI

31 Standard Penetration Test (STP) videos Cone Penetrometer Test (CPT) FHWA NHI

32 Cone Penetrometer Test (CPT) FHWA NHI Cone Penetrometer Test (CPT) FHWA NHI

Cone Penetrometer Test (CPT) ADVANTAGES DISADVANTAGES Fast and continuous profiling Economical and productive Results not operatordependent Strong theoretical basis in interpretation Particularly

33 Cone Penetrometer Test (CPT) ADVANTAGES DISADVANTAGES Fast and continuous profiling Economical and productive Results not operatordependent Strong theoretical basis in interpretation Particularly suitable for soft soils High capital investment Requires skilled operator to run Electronic drift, noise, and calibration No soil samples are obtained Unsuitable for gravel or boulder deposits FHWA NHI Flat Plate Dilatometer (DMT) FHWA NHI

Flat Plate Dilatometer (DMT) FHWA NHI-01-031 Flat Plate Dilatometer (DMT) ADVANTAGES DISADVANTAGES Simple and Robust Repeatable & Operator- Independent Quick

34 Flat Plate Dilatometer (DMT) FHWA NHI Flat Plate Dilatometer (DMT) ADVANTAGES DISADVANTAGES Simple and Robust Repeatable & Operator- Independent Quick and economical Difficult to push in dense and hard materials Primarily relies on correlative relationships Need calibrations for local geologies FHWA NHI

35 Pressuremeter Test (PMT) FHWA NHI

Pressuremeter Test (PMT) FHWA NHI-01-031 Pressuremeter Test (PMT) ADVANTAGES DISADVANTAGES Theoretically sound in determination of soil parameters Tests larger zone of soil mass than other in-situ

36 Pressuremeter Test (PMT) FHWA NHI Pressuremeter Test (PMT) ADVANTAGES DISADVANTAGES Theoretically sound in determination of soil parameters Tests larger zone of soil mass than other in-situ tests Develop complete σ-ε-τ curve. Complicated procedures; requires high level of expertise in the field Time consuming and expensive (good day gives 6 to 8 complete tests) Delicate, easily damaged FHWA NHI

37 Vane Shear Test (VST) FHWA NHI Vane Shear Test (VST) FHWA NHI

38 Vane Shear Test (VST) ADVANTAGES DISADVANTAGES Assessment of undrained strength Simple test and equipment Measure in-situ clay sensitivity Long history of use in practice Limited application to soft to stiff clays Slow and time-consuming Raw undrained strength needs (empirical ) correction Can be affected by sand lenses and seams FHWA NHI Downhole Geophysics ADVANTAGES DISADVANTAGES Nondestructive and/or noninvasive Fast and economical testing Theoretical basis for interpretation Applicable to soils and rocks No samples or direct physical penetration Models assumed for interpretation Affected by cemented layers or inclusions Results influenced by water, clay, & depth FHWA NHI

39 Relevance of In-situ Tests to Different Soil Types FHWA NHI Obstructions 39

40 Taking samples (extruding from Shelby Tube) Cutting the sample 40

41 Cutting a sample to testing size Testing a sample with Torvane 41

appropriate Put in appropriate container/box Not left in unattended

42 Sample Preservation Clearly, permanently and accurately labeled, and position recorded on drill log Sealed against moisture loss if appropriate Put in appropriate container/box Not left in unattended vehicles to freeze or over heat, taken to office/lab in a timely fashion Waxing samples 42

43 AASHTO Man Sub Inv Boring Logs 1. Description and classification of each layer of soil 2. Depth for each 3. Depths and results of field tests 4. Information a) Boring (hole) number b) Start and finish date c) Name of driller and logger d) Elevation at top of hole e) Depth of hole and reason for terminatioin 43

44 Boring Logs f. Diameter of any casing used g. Size of hammer and free fall distance h. Blows per 0.3 m i. Description and size of sampler j. Size of drive hammer and free fall distance k. Blow count (SPT) each 150 mm drive of sampler l. Type of drilling machine used m. Drilling time for each core run n. Sample recovery o. Project identification p. Client name Boring Logs 5. Notes regarding any other pertinent info a) Dept of observed groundwater, time, conditions b) Artesian condition c) Obstructions d) Drilling difficulties (caving, coring boulders, surging of sands, caverns) e) Loss of circulation f) Drilling mud and casing as needed g) Odor of sample 6. Any other information required 44

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46 Borehole Sealing Cement grout from the bottom Bentonite Remove casing Bad Actors Organic Soils Normally consolidated clays Metastable soils (loess, alluvial, mud flows) Caliche Expansive soils Loose granular soils Sensitive clays 46

47 Bad Actors Noxious or explosive gasses Slope movements Kettle holes Meander loops and cutoffs Artificial fill Karst Weathered shale Abandoned mines Frozen soils SLIDE SHOW: Geological Environments 47

48 Fluvial / Breccia Images from Monro and Wicander Fluvial Variability Images from Monro and Wicander 48

49 Braided River / Point Bars Images from Monro and Wicander Oxbow Meanders Images from Monro and Wicander 49

50 River Terrace / Delta Images from Monro and Wicander Aluvial Fans / Talus Images from Monro and Wicander 50

51 Glacial Variability Images from Monro and Wicander 51

52 Till / Moraine Eskers Images from Monro and Wicander 52

53 Esker Cross section of an esker 53

54 Outwash Images from Monro and Wicander Buried Valleys 54

55 Beach Deposit Images from Monro and Wicander Raised beach ridges 55

56 Raised beach ridges (air photo) Aolean: Desert Pavements Images from Monro and Wicander 56

57 Desert Pavement Images from Monro and Wicander Salt Flats / Dunes Images from Monro and Wicander 57

58 Tropical Regions: Weathering Products Images from Monro and Wicander Drilling gone wrong 58

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Instructional Objectives

GE 343 SUBSURFACE EXPLORATION CH 8 Rock Drilling, Testing, and Sampling Text Ch. 7. Dr. Norbert H. Maerz Missouri University of Science and Technology (573) 341-6714 norbert@mst.edu Instructional Objectives