1 MPa = 150 psi 10 kn = 1 ton 25 mm = 1 inch

Transcription

1 INTELLIGENT COMPACTION: AN OVERVIEW Developed by Jean-Louis Briaud Department of Civil Engineering Texas A&M University Presented to the 5 th Idaho Asphalt Conference, October 27, 5 By Fouad Bayomy Department of Civil Engineering, University of Idaho ACKNOWLEDGEMENTS Chris Dumas, FHWA Hans Kloubert, BOMAG Roland Anderegg, AMMANN Bob Horan, SALUT 1 MPa = 15 psi 1 kn = 1 ton 25 mm = 1 inch INTELLIGENT COMPACTION: AN OVERVIEW Current practice Future practice Modulus and dry density Compactions methods Intelligent Compaction Principle Equipment and instrumentation How to get the stiffness How to get the modulus Specs Future needs CURRENT PRACTICE Based on Density LAB: Proctor test to get dry density vs. water content curve SPEC: x% of γ dmax within range of w opt FIELD: Compact and check that γ d and w meet the specs CURRENT PRACTICE Based on Density LAB : Proctor Test Dry Density (kn/m 3 ) γ dmax 1 S =.9 S = 1 1 w opt

2 SPECIFICATIONS. FIELD CURRENT PRACTICE Based on Density X % of γ dmax within range of w opt Nuclear Density Meter For γ d and w Dry Density: Advantages and Disadvantages 1. Advantages Accumulated knowledge Well defined parameter Indication of solids per unit volume 2. Disadvantages Not related to design Not very sensitive Not easy to measure quickly in field FUTURE PRACTICE Based on Modulus LAB: Modulus test to get modulus vs. water content curve SPEC: x% of E max within range of w opt FIELD: Intelligent compaction and check that E max and w meet the specs FUTURE PRACTICE Based on Modulus LAB : Modulus Test Modulus (MPa) E max Clay Sand 6 1 w 1 1 opt SPECIFICATIONS X % of E max within range of w opt FIELD Intelligent Compaction E IC FUTURE PRACTICE Based on Modulus Modulus Meter For E and w Modulus: Advantages and Disadvantages 1. Advantages Directly related to design Very sensitive to water content Easy to measure quickly in field 2. Disadvantages Many influencing factors No lab test to get E vs. w No target values New concept 2

3 Stiffness or Modulus? K = F/x in MN/m E ~ σ/ε in MN/m 2 or MPa E = α F/Bx K = F/x = EB/α Stiffness or Modulus? Stiffness depends on the size of the roller. Modulus does not; it is a property of the soil only. Use the modulus, not the stiffness CALCULATION OF MODULUS Which Modulus? DEFINITION Initial Secant Tangent Unload-Resilient Cyclic Reload WHICH MODULUS? Which Modulus? STATE FACTORS Density Structure Water content Stress history Cementation 3

4 Which Modulus? WHICH MODULUS? LOADING FACTORS Stress level Strain level Strain rate Number of cycles Drainage Which Modulus? PLATE MODULUS in FIELD Which Modulus? PLATE MODULUS in LAB 25 Load ( N) 15 1 EL=.91 MPa Er= MPa 5 (E.CVEN#1) (/2/3) Displacement(mm) BPT: Briaud Plate Test BPT: Briaud Plate Test Range of Modulus Asphalt Modulus Steel: Concrete: Wood, Plastic: Rock: Asphalt: Soil: Mayonnaise:, MPa, MPa 13, MPa 2, to 3, MPa 15 to 25 MPa 5 MPa to 1 MPa.5 MPa 15 to 3 MPa at 1 o C 3 to 5 MPa at o C 25 MPa at -1 o C

5 NGES Sand Compaction Curve Mold #5 Compaction Curve Mold # NGES Silty Sand (Mold #5) Modulus (MPa 3 1 Dry Unit Weight (kn/m^3) NGES Silty Sand (Mold #6) NGES Silty Sand 5 Modulus (MPa 3 1 Dry Unit Weight (kn/m^3) Modulus (Mpa 3 1 Dry Unit Weight (kn/m^3) NGES Sand + Porcelain Clay Compaction Curve Mold #5 Compaction Curve Mold #6 NGES Sand + Porcelain Clay (Mold #5) Modulus 3 1 Dry Unit Weight (kn/m^3))

6 NGES Sand + Porcelain Clay (Mold #6) Modulus 3 1 Dry Unit Weight (kn/m^3) NGES Sand + Porcelain Clay Modulus (Mpa) 6 Dry Unit Weight (kn/m^3) Dry Dry Unit Weight (kn/m 3 3 ) ) For Soils 1. Density? 2. Modulus? 3. Water Content? For Asphalt 1. Density? 2. Modulus? 3. Temperature? Only one of those three is not enough Two of those three are sufficient All three would be nice x&& d From Acceleration to Stiffness F mx && + mrω 2 cos( Ω t) + ( m + m) g B d d u u f d FB kbxd + dbx& d F B : soil-drum-interaction-force m d : mass of the drum (kg) x d : vert. disp. of drum (m) x&& d : acceleration of drum m f : mass of the frame (kg) m u : unbalanced mass (kg) r u : radial distance for m u Ω = 2π f g: acc. due to gravity (m/sec 2 ) f: frequency of rotating shaft (Hz) x& d : velocity of drum d B : damping coefficient (d B ~.2) k B : stiffness of soil m R g F B m w R g F Flieh= mew 2 cos(φ) x w Force-Displacement Curves Energy Expanded Soil Reaction Force (kn) Soil Reaction Force (kn) Fx x 3rd Pass Fx x Compaction Energy 1st Pass 2nd Pass Fx max Rebound Energy Fstat Drum Oscillation (mm) Fstat Drum Oscillation (mm) From BOMAG From BOMAG 6

7 Stiffness or Modulus? K = F/x in MN/m E ~ σ/ε in MN/m 2 or MPa E = α F/Bx K = F/x = EB/α Stiffness or Modulus? Stiffness depends on the size of the roller. Modulus does not; it is a property of the soil only. Use the modulus, not the stiffness x&& d From Stiffness to Modulus F B H. Hertz, 195 : x&& d From Stiffness to Modulus (theoretical) b = 2 R(1 ν ) FB π E l G. Lundberg, 1939 : 2 1 ν FB 2 l δ = (1,6+ ln ) δ E l π b EL π kb = π L E 2 ( 1 ν ) 2.1+ ln 2 2 ( 1 ν ) ( mf + md) R g [ MN m] b δ = f ( F, E) B From Stiffness to Modulus (experimental) Soil Modulus for Intelligent Compaction Soil: 5 MPa unacceptable MPa excellent From AMMANN 7

8 Specifications based on Modulus Laying and compaction specification for road construction in Germany Soil layers Density Bearing capacity Eveness (Standard Proctor) (load bearing test, EV2) ( m straight edge) Subbase 1-13 % * 1-15 MN/m² * mm Capping layer 1-13 % * 1-1 MN/m² * mm Formation 97-1 % * 5 - MN/m² * 6 mm * depending on road classification and road design Three Compaction Control Methods Conventional Compaction Continuous Control Compaction Intelligent Compaction From BOMAG Conventional Compaction (static or vibratory smooth drum or sheep-foot) Continuous Vibratory Compaction Control Instrumented vibrating rollers Measure roller accel. as a function of time Calculate a soil stiffness or modulus Modulus preferable because indep. of roller Modulus is compared to target value (specs) The modulus value tells the operator if the specified compaction level is reached Intelligent Vibratory Compaction Recompaction of soft formation area with VARIOCONTROL automatic mode, presetting ( target value ) EVIB = MN/m² Instrumented vibrating rollers Measure roller accel. as a function of time Calculate a soil modulus That modulus is independent of the roller Intelligent roller modifies automatically instantaneously settings (force, ampl., freq.) to meet the target modulus

9 Equipment Intelligent Compaction Tests in the U.S.A. BOMAG (Germany) AMMANN (Switzerland) GEODYNAMIK (Sweden) FUTURE NEEDS 1. Reference modulus = plate test? Example of same modulus test in lab and in field BCD Test: Briaud Compaction Device 2. Develop simple lab modulus test 3. Study modulus vs water/asph. Content. Demonstrate that IC is better than CC 5. Calibrate rollers against plate modulus 6. Use same modulus test (lab and field) BCD on Proctor Mold BCD in the Field FUTURE NEEDS Summary 7. Develop specs based on modulus for diff. pavement cond.. Can the asphalt modulus be isolated from the soil modulus 9. Use modulus control equipment 1. Demonstrate the IC equipment What is IC? Advantage and drawbacks Contract types Theory is well established Equipment is readily available Research Needs 11. First International Conference on Compaction 9

10 THANK YOU 1