Miniature Pressuremeter and Miniature Cone Penetrometer Testing in Calibration Chamber with Unsaturated Soil Beds

1. Miniature Pressuremeter and Miniature Cone Penetrometer Testing in Calibration Chamber with Unsaturated Soil Beds By Norman K. Tan

2. Outline • Introduction • Objective • Research task • Why calibration chamber? • OU calibration chamber • Preparation of soil beds • Test results • Research question.

3. Introduction • Cone Penetrometer (CPT) & Pressuremeter (PMT) • Popular in situ testing devices • Give estimates of in situ soil properties • Methods developed to interpret results focus around: • Saturated soil • Dry sand • About 1/3 of earth ~ arid/semi arid regions • Behavior of unsaturated soil is different from saturated soil • Motivation: No methods for interpreting CPT & PMT in unsaturated soil

4. Objective • Develop a method to predict PMT and CPT responses for various matric suction based on one test result

5. Research Task • Calibration chamber testing • Numerical and analytical analysis and modeling • Laboratory testing

6. Calibration Chamber Testing Modeling Laboratory Testing ~Soil properties Research task

7. Why Calibration Chamber? • Field Testing • Easy and cheaper • Lack of control over the boundary conditions • Heterogeneous of soil • Unknown stress history, stress state, etc. • Calibration Chamber Testing • Controlled environment • Boundary condition • Stress state • Homogeneous soil beds • Etc.

8. OU Calibration Chamber (OUCC) • Allows independent control of radial & axial stress (BC1) • Designed working pressure ~ 1380 kPa • Capable to perform axis translation • Pore air & pore water can be controlled independently • Burettes system: measure water volume change • DAVI: measure diffused air volume

9. LVDTs ~ measure total volume change • Soil beds • diameter: 610 mm • Height: 450 mm to 1350 mm

10. Preparation of Soil Beds • Soil preparation: • Oven dried • Pass #10 sieve • Mixed with water in large concrete mixer • Store in 5 gallon pails for minimum of 1 day • Soil bed consolidation • 35 kPa increment • Up to 103 kPa • Soil used: • Minco Silt • From Tuttle, OK • CL-ML soil • PI: 8 • Soil bed preparation: • Statically compacted • 152 mm/layer

12. OU Miniature Pressuremeter (MPMT) • Diameter: 15.2 mm • Length: 130 mm • H/D: 8.5 • Dsoilbed/Dprobe: 40 • Test Depth: • 267 mm (center of probe) • 495 mm (center of probe)

13. OU Miniature Cone Penetrometer (MCPT) • Diameter: 8.9 mm • Dsoilbed/Dprobe: 68.5 • Penetration rate: 0.5 cm/sec

14. Typical MPMT Results • Limit Pressure ~ defined as pressure at which vol. of the cavity is twice of initial soil cavity volume ~ determined using 1/v vs P plot • From test: CCT6 PMT 6-2

15. Summary of MPMT Results

16. MPMT Results

17. MPMT Results

18. MPMT Results

19. MPMT Results

20. MPMT Results

21. MCPT Results • w: 6%

22. MCPT Results • w: 8%

23. MCPT Results • w: 10%

24. MCPT Results • CPT 1 A ~ w: 8%

25. MCPT Results: qc Histogram

26. MCPT Results: m0 of qc

27. MCPT Results: m0 of qc

28. CCT3B MCPT Results

29. MCPT Results

30. MCPT Results

31. Research Questions ??? • What is the true value of H, v for Minco Silt? • Does c`, `, b varies with initial water content, dry unit weight? How significant? • Are the interpreted matric suctions the true matric suctions? • Explanations for the PMT response: ~ trend in ua-uw vs. Pl plot

32. Thank you !!!