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Miniature Pressuremeter and Miniature Cone Penetrometer Testing in Calibration Chamber with Unsaturated Soil Beds PowerPoint Presentation
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Miniature Pressuremeter and Miniature Cone Penetrometer Testing in Calibration Chamber with Unsaturated Soil Beds. By Norman K. Tan. Outline. Introduction Objective Research task Why calibration chamber? OU calibration chamber Preparation of soil beds Test results Research question.

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slide1

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

By

Norman K. Tan

outline
Outline
  • Introduction
  • Objective
  • Research task
  • Why calibration chamber?
  • OU calibration chamber
  • Preparation of soil beds
  • Test results
  • Research question.
introduction
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
objective
Objective
  • Develop a method to predict PMT and CPT responses for various matric suction based on one test result
research task
Research Task
  • Calibration chamber testing
  • Numerical and analytical analysis and modeling
  • Laboratory testing
research task1

Calibration Chamber Testing

Modeling

Laboratory Testing

~Soil properties

Research task
why calibration chamber
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.
ou calibration chamber oucc
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
slide9
LVDTs ~ measure total volume change
  • Soil beds
    • diameter: 610 mm
    • Height: 450 mm to 1350 mm
preparation of soil beds
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
ou miniature pressuremeter mpmt
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)
ou miniature cone penetrometer mcpt
OU Miniature Cone Penetrometer (MCPT)
  • Diameter: 8.9 mm
  • Dsoilbed/Dprobe: 68.5
  • Penetration rate: 0.5 cm/sec
typical mpmt results
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
mcpt results3
MCPT Results
  • CPT 1 A ~ w: 8%
research questions
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