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.

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

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

Research Task

• Calibration chamber testing

• Numerical and analytical analysis and modeling

• Laboratory testing

Research task

Calibration Chamber Testing

Modeling Laboratory Testing~Soil properties

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)• 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

• LVDTs ~ measure total volume change

• Soil beds

– diameter: 610 mm

– Height: 450 mm to 1350 mm

Soil BedSoil BedSoil BedSoil BedSoil BedSoil BedSoil BedSoil BedSoil BedSoil BedSoil BedSoil BedSoil BedSoil BedSoil BedSoil BedSoil BedSoil BedSoil Bed

Preparation of Soil Beds• Soil used:

– Minco Silt– From Tuttle, OK– CL-ML soil– PI: 8

• Soil bed preparation:– Statically compacted– 152 mm/layer

• 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

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)

• Diameter: 8.9 mm

• Dsoilbed/Dprobe: 68.5

• Penetration rate: 0.5 cm/sec

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

Summary of MPMT Results(kpa) (kpa) (kpa) (%) (%) (kN/m3) (kPa)

PMT2-1 14836 23396 839 10.1 14.1 13.7 23.8PMT2-2 14154 23879 766 11.0 15.4 13.7 19.6PMT3-1 21113 22608 1341 5.9 7.8 13.0 59.7PMT3-2 31434 31606 1585 5.4 7.4 13.3 60.1PMT4-1 7943 12329 641 12.5 18.0 14.2 13.2PMT4-2 7868 12752 605 12.8 18.7 14.3 12.0PMT5-1 13101 25098 771 7.8 10.7 13.5 41.5PMT5-2 17415 28955 787 8.1 11.2 13.5 38.6PMT6-1 26023 57144 1026 8.7 12.3 13.9 32.0PMT6-2 20629 60287 977 8.6 12.5 14.3 31.1PMT8-1 9875 15789 525 7.3 9.5 12.8 49.7PMT8-2 8811 18972 545 7.2 9.4 12.8 50.3PMT9-1 15237 20572 766 8.8 12.1 13.5 33.2PMT9-2 12050 22611 734 8.7 12.1 13.5 33.3PMT10-1 15166 35707 835 8.0 11.1 13.5 39.1PMT10-2 18578 37243 770 8.2 11.3 13.5 37.6

PMT11-1C 11224 29656 490 6.1 8.0 12.9 58.8PMT11-2C 14208 39401 525 5.9 7.7 12.8 59.7PMT11-1S 11836 25794 488 6.0 8.0 13.1 58.8PMT11-2S 13547 26092 524 6.0 7.9 12.9 59.2PMT11-1E 8668 18579 488 6.1 7.8 12.7 59.4PMT11-2E 13448 22372 580 5.9 7.6 12.7 59.9PMT11-1W 12411 19567 528 6.2 8.1 12.8 58.4PMT11-2W 10338 18234 507 5.9 7.6 12.6 60.0

Test ID: Ep Er PL

interpretedw d

MPMT Results

0

200

400

600

800

1000

1200

1400

1600

1800

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0

Interpreted Matric Suction (kPa)

Lim

it P

ress

ure

(kP

a)

MPMT Results

0

200

400

600

800

1000

1200

1400

1600

1800

12.4 12.6 12.8 13.0 13.2 13.4 13.6 13.8 14.0 14.2 14.4 14.6

Dry Unit Weight (kN/m^3)

Lim

it P

ress

ure

(kP

a)

MPMT Results

12.4

12.612.8

13.0

13.213.4

13.613.8

14.0

14.214.4

14.6

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0

Interpreted Matric Suction (kPa)

Dry

Un

it W

eig

ht

(kN

/m^

3)

MPMT Results

0

5000

10000

15000

20000

25000

30000

35000

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0

Interpreted Matric Suction (kPa)

Ep

(kP

a)

MPMT Results

0

5000

10000

15000

20000

25000

30000

35000

12.4 12.6 12.8 13.0 13.2 13.4 13.6 13.8 14.0 14.2 14.4 14.6

Dry Unit Weight (kN/m^3)

Ep

(kP

a)

MCPT Results

• w: 6%

CPT 1 A

qc (kN/m2)

0

1000

2000

3000

4000

5000

6000

7000

Dep

th (

cm)

0

20

40

60

80

100

120

140

CPT 1 B

qc (kN/m2)

0

1000

2000

3000

4000

5000

6000

7000

CPT 1 C

qc (kN/m2)

0

1000

2000

3000

4000

5000

6000

7000

CPT 1 D

qc (kN/m2)

0

1000

2000

3000

4000

5000

6000

7000

8000

MCPT Results

• w: 8%

CPT 2 A

qc (kN/m2)

0

1000

2000

3000

4000

5000

6000

7000

Dep

th (

cm)

0

20

40

60

80

100

120

140

CPT 2 B

qc (kN/m2)

0

1000

2000

3000

4000

5000

6000

7000

CPT 2 C

qc (kN/m2)

0

1000

2000

3000

4000

5000

6000

7000

CPT 2 D

qc (kN/m2)

0

1000

2000

3000

4000

5000

6000

7000

8000

MCPT Results

• w: 10%

CPT 3 A

qc (kN/m2)

0

1000

2000

3000

4000

5000

6000

7000

Dep

th (

cm)

0

20

40

60

80

100

120

140

CPT 3 B

qc (kN/m2)

0

1000

2000

3000

4000

5000

6000

7000

CPT 3 C

qc (kN/m2)

0

1000

2000

3000

4000

5000

6000

7000

CPT 3 D

qc (kN/m2)

0

1000

2000

3000

4000

5000

6000

7000

8000

MCPT Results

• CPT 1 A ~ w: 8%

qc (kN/m2)

0

1000

2000

3000

4000

5000

6000

7000

Dep

th (

cm)

0

20

40

60

80

100

120

140

Dry Unit Weight (kN/m3)

10 11 12 13 14

Gravimetric Water Content (%)

4.0

4.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

8.5

9.0

MCPT Results: qc Histogram CPT1A

Rel

ativ

e Fr

eque

ncy

(%)

0.000.020.040.060.080.100.120.140.16

CPT1B CPT1C CPT1D

CPT2A

Rel

ativ

e Fr

eque

ncy

(%)

0.000.020.040.060.080.100.120.14

CPT2B CPT2C CPT2D

CPT3A

qc (kPa)

0 1000 2000 3000 4000 5000 6000 7000

Rel

ativ

e Fr

eque

ncy

(%)

0.000.020.040.060.080.100.120.14

CPT3B

qc (kPa)

0 1000 2000 3000 4000 5000 6000 7000

CPT3C

qc (kPa)

0 1000 2000 3000 4000 5000 6000 7000

CPT3D

qc (kPa)

0 1000 2000 3000 4000 5000 6000 7000 8000

MCPT Results: 0 of qc

 

CPT1 CPT2 CPT3

A 3888 2883 2979B 4055 3208 2779C 4006 2978 2908D 3918 3101 3035

AVERAGE 3967 3043 2925

59.2 43.6 24.4

13.2 13.5 14.0Average Dry Unit Weight

(kN/m3)

o o

f qc (k

Pa)

Average Interpreted Matric Suction (kPa)

MCPT Results: 0 of qc

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 10 20 30 40 50 60 70

Average Interpreted Matric Suction (kPa)

o q

c (k

Pa)

MCPT Results0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

0 1000 2000 3000 4000 5000 6000 7000 8000

qc (kPa)

Dep

th (

cm)

CCT3B

MCPT Results

HISTOGRAM (MEAN)

MIN-MAX MEAN

OVERALL MEDIAN

CPT1A 59 3888 4073 3739CPT1B 59 4055 4133 3961CPT1C 59 4006 4062 4012CPT1D 59 3918 4056 3814CPT2A 43 2883 3224 2761CPT2B 43 3208 3622 3208CPT2C 44 2978 3347 2971CPT2D 45 3101 3170 3029CPT3A 27 2979 3362 3157CPT3B 22 2779 3314 2883CPT3C 23 2908 3047 2858CPT3D 27 3035 3340 2970

qc (kPa)INTERPRETED MATRIC

SUCTION (kPa)TEST ID

MCPT Results

2000

2500

3000

3500

4000

4500

0 10 20 30 40 50 60 70

Interpreted Matric Suction (kPa)

qc(

kPa)

HISTOGRAM (MEAN) MIN-MAX MEAN OVERALL MEDIAN

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

Thank you !!!