USE OF DMT IN GEOTECHNICAL

DESIGN WITH EMPHASIS ON

LIQUEFACTION ANALYSIS

Presented By: Muhammad Ali Rehman

Overview

Introduction

Data Interpretation

DMT Correlations

Liquefaction

Liquefaction Assessment

Case Study

Conclusions

References

DMT

Equipment Layout

Test Procedure

INTRODUCTION

Dilatometer Test (DMT)

Developed by Professor Silvano

Marchetti (Italy).

Published test procedure &

correlations in 1980.

DMT measures the lateral deflection

of soil.

Equipment Layout

Fig: General Layout of DMT

Test Procedure

DMT in-situ testing involves expanding membrane

by using nitrogen gas.

The primary way of using DMT results is to

interpret them in terms of common soil

parameters.

DATA INTERPRETATION

Dilatometer Test Parameters

Primary parameters of DMT.

Material Index

ID = (p1 – p0) / (p0 – u0)

Horizontal Stress Index

KD = (p1 – p0) / σ´v0

Dilatometer Modulus

ED = 34.7 (p1 – p0)

Pore-pressure Index

UD = (p2 – u0) / (p0 – u0)

• DMT parameters, ID, KD, and ED are used in

subsequent soil analysis.

DMT CORRELATIONS

Correlations

Soil Behavior

Over-consolidation

Relative Density

Undrained Shear Strength

Constrained Modulus

Compression Ratio

Settlement Prediction

Skin friction of Driven Piles

SPT N-value and Dilatometer Modulus

1. Behavior of Soil

Soil behavior chart introduced by Marchetti et al.

(1980).

ID<0.6 : Clays

0.6≤ID≤1.8 : Silts

ID>1.8 : Sands

2. Over-Consolidation Ratio (OCR)

Original correlation proposed by Marchetti et al.

(1980):

OCRDMT = (0.5 x KD)1.56

Confirmed by a comprehensive collection of data

by Kamei & Iwasaki (1995) for clays.

Finno (1993)

Over-Consolidation Ratio (OCR)

Kamei & Iwasaki (1995) Finno (1993)

3. Relative Density

Reyna & Chameau (1991)

and

Tanaka & Tanaka (1998)

Robertson & Campanella

4. Undrained Shear Strength

Marchetti et al. (1980):

cu = 0.22 σ'v0 (0.5 KD)1.25

Undrained Shear Strength

Comparison of undrained shear strength by DMT

and other tests, at National Research Site,

Bothkennar (UK):

Nash et al. (1992)

5. Constrained Modulus : MDMT

Obtained by applying correction factor RM to ED

MDMT = RM . ED

RM is the function of material index (ID) and

horizontal stress index (KD).

Increases with KD while ID has lesser effect on the RM

value.

Generally varies from 1 to 3.

6. Compression Ratio

Marchetti et al. (1980)

Pre-consolidated Clays

M = σ’p (2.3/CR)

Normally Consolidated Clays

M = σ’v (2.3/CR)

7. Settlement Prediction

Predicting the settlement of shallow foundations

(particularly for Sands) is one of the best

applications of DMT.

Calculated by means of expression:

S = [ Δσv/MDMT ] ΔZ

Totani, Marchetti, Monaco &

Calabrese (2001)

8. Skin Friction for Driven Piles in Clay

Powell et al. (2001 b), developed a method for the design of piles driven in clay.

Method predicts pile skin friction qs, from ID and (p1

- p0):

ID < 0.1 : qs /(p1 - p0 ) = 0.5

0.1 < ID < 0.65 : qs /(p1 - p0 ) = -0.73077 ID + 0.575

ID > 0.65 : qs /(p1 - p0 ) = 0.1

9. SPT N-value & ED

Mayne & Frost

Introduction

Liquefiable Soils

Liquefaction Assessment

LIQUEFACTION

Liquefaction

“Transformation of coarse grained soil from a solid state into a liquid state”

Excessive hydrostatic pressure build-up & reduction of effective stress

sudden shock

cyclic loading.

Devastating effects of structure:

Tilting of high rise buildings

Ground subsidence

Surface rupture

Collapse

Liquefiable Soils

Loose granular soils are potentially susceptible to

liquefaction.

Fine grained soils (such as silts and clays) are non-

liquefiable.

Andrews & Martin (2000) suggested:

Potentially Liquefiable: soils having, CF < 10% & LL <

32%

Non-Liquefiable: soils having, CF > 10% & LL ≥ 32%

Liquefaction Assessment

Glaser and Chung (1995):

Loose granular soils densify on sampling.

Laboratory measurements demonstrate higher cyclic strength

In-situ testing is preferred.

“Simplified Procedure” for liquefaction assessment,

proposed by Seed & Idriss (1971).

To evaluate the loading to a soil caused by an earthquake (by

CSR)

To evaluate the resistance of a soil to triggering of

liquefaction (by CRR)

Liquefaction Assessment

Factor of Safety against the occurrence of

liquefaction is defined as:

FS = CRR7.5 /CSR7.5

If FS < 1, liquefaction will be triggered.

Cyclic Stress Ratio (CSR)

CSR is the measure of intensity of cyclic loading during an earthquake.

Obtained by formula, developed by Seed & Idriss(1971):

CSR 7.5 = 0.65 (amax / g) . (σv0 / σ’vo) . rd

amax is the peak horizontal ground acceleration generated by the earthquake.

rd is the stress reduction factor.

Cyclic Stress Ratio (CSR)

Seed & Idriss porposed:

rd is the function of stratigraphy and depth.

Has a value of 1.0 at ground surface, tends to reduce

with depth.

Seed and Idriss (1971)

Cyclic Stress Ratio (CSR)

Youd et al. (2001)

rd = [1.0 – 0.00765z] (z ≤ 9.2m)

rd = [1.174 – 0.0267z] (9.2 < z ≤ 23m)

rd = [0.744 – 0.008z] (23 < z ≤ 30m)

rd = 0.5 (z > 9.2m)

Cyclic Resistance Ratio

In-situ test Procedures:

Standard Penetration Test

Cone Penetration Test

Shear wave velocity test

Dilatometer Test

DMT Based CRR Evaluation

Include:

Marchetti (1980)

Roberstson & Campnella (1986)

Reyna & Chameau (1991)

Monaco et al. (2005)

Grasso & Maugeri (2006)

Monaco & Marchetti (2007)

Tsai et al. (2001, 2009)

DMT Based CRR Evaluation

Marchetti (1980) proposed the basic correlation:

CRR = (KD/10)

Refined by Monaco et al. (2005):

CRR7.5 = 0.0107KD3 − 0.0741KD

2 + 0.2169KD – 0.1306

Grasso & Maugeri (2006) further updated Monaco

et al. (2005) model into:

CRR7.5 = 0.0908KD3 − 1.0174KD

2 + 3.8466KD – 4.5369

DMT Based CRR Evaluation

Curves for CRR (Reyna & Chameau

1991)

Clean sand is safe against liquefaction for following KD

values:

Non seismic areas:KD > 1.7

Low seismicity areas :KD > 4.2

Medium seismicity areas: KD > 5.0

High seismicity areas:KD > 5.5

Performance of DMT Based Liquefaction

Evaluation of Chi-Chi Earthquake, Taiwan (1999)

by Tsai et al. (2001)

Case Study

Chi-Chi Earthquake

21 September 1999, at 1:47 am,

an Earthquake hit Taiwan.

7.6 magnitude

Epicenter near Chi-Chi (town in

Nantou County)

2400 deaths, 8373 Injuries

Damage of US$30 billion.

Extensive field investigation after

earthquake was conducted by

NCREE.

In-situ SPT & CPT were performed.

Collection of SPT Data

Liquefaction sites:

Wufeng, Nantou, Yuanlin & Zhangbin

Total 31 SPT Cases

24 liquefied

7 non-liquefied

Collection of SPT Data

Area Test NumberTriggering of

Liquefaction

Wufeng SPT9 Yes

1 No

Nantou SPT7 Yes

1 No

Yuanlin SPT8 Yes

5 No

SPT Based Method

Seed et al. established chart for estimating SPT

based CRR7.5 :

Seed et al. (1985)

SPT Based Method

The CRR7.5 curves were further modified by Youd et al. (2001) and formulated as:

CRR7.5 = 𝟏

𝟑𝟒− (𝑵𝟏)𝟔𝟎+

(𝑵𝟏)𝟔𝟎

𝟏𝟑𝟓+

𝟓𝟎

(𝟏𝟎 (𝑵𝟏)𝟔𝟎 + 𝟒𝟓)𝟐−

𝟏

𝟐𝟎𝟎

Valid for (𝑵𝟏)𝟔𝟎 < 30

Sandy soils are considered to be non-liquefiable for (𝑵𝟏)𝟔𝟎 > 30.

Idriss and Boulanger (2006) proposed a new equation:

CRR7.5 = Exp(𝑵𝟏)𝟔𝟎

14.4+

(𝑵𝟏)𝟔𝟎

126

2−

(𝑵𝟏)𝟔𝟎

23.6

3+

(𝑵𝟏)𝟔𝟎

25.4

4− 2.8

DMT Based Method

DMT parameters, KD and ED are used to develop

DMT based CRR7.5 boundary curves.

Two boundary curves, CRR7.5-KD & CRR7.5-ED were

established by Tsai et al. (2001), following the

existing CRR7.5-(N1)60 curve.

Tsai et al. (2001) established the following

correlations to develop DMT based CRR7.5 curves.

(N1)60-KD

(N1)60-ED

DMT Based Method

Tsai et al. (2001):

(𝑵𝟏)𝟔𝟎 = 0.185KD3 − 2.75KD

2 + 17KD – 15

(𝑵𝟏)𝟔𝟎 = 0.00022ED3 − 0.02ED

2 + 0.9ED – 3

DMT Based Method

Based on above correlations, Tsai et al. (2001)

developed the DMT based CRR7.5 boundary curves.

CRR7.5 = Exp𝑲𝑫

8.8

3−

𝑲𝑫

6.5

2+

𝑲𝑫

2.5− 3.1

CRR7.5 = Exp𝑬𝑫

49

3−

𝑬𝑫

36.5

2+

𝑬𝑫

23− 2.7

DMT Based Method

DMT Based Method

CRR curves proposed by Monaco

(2005), Grasso & Maugeri (2006)

and Tsai (2009)

CONCLUSION

Conclusion

DMT is relatively quick in-situ method which estimates a number of parameters, that can be effectively used in geotechnical design.

DMT is capable of taking into account the soil structure, aging and consolidation effects, which generally influence the liquefaction potential of soil (Tsai et al. 2001).

Tsai et al. (2001) study shows that the accuracy of DMT based CRR7.5 curves for Liquefaction assessment is satisfactory.

Liquefaction assessment is relatively fast and reliable as compared to SPT, which takes longer time to supplement SPT with lab testing.

Conclusion

However, it is desirable to directly conduct DMTs in

the liquefied and non-liquefied areas of

earthquake to obtain more KD and ED data of soils

for further validating the developed DMT-based

liquefaction evaluation method although the results

of this study are preliminarily satisfactory

REFERENCES

References

Marchetti, S. (1980). "In Situ Tests by Flat Dilatometer." J. Geotech. Engrg. Div., ASCE, 106, No.GT3, 299- 321.

G. Totani, S. Marchetti, P. Monaco & M. Calabrese. Use of Flat Dilatometer Test in Geotechnical Design, Intl. Conf. on In-situ Measurement of Soil Properties (2001)

Monaco, P., Marchetti, S., Totani, G. and Calabrese, M. (2005). “Sand liquefiability assessment by Flat Dilatometer Test (DMT).” Proc. XVI ICSMGE, Osaka, 4, 2693-2697

Robertson, P.K., and R.G. Campanella, [1986]. “Estimating liquefaction potential of sands using the flat plate dilatometer. Geotech. Testing J., Vol. 9, No. 1, pp. 38–40.

Tsai, Tung and Lee (2001) . Performance of DMT based liquefaction evaluation method on case history of Chi-Chi Earthquake

Bambang Setiawan,(2011) “Assessing Liquefaction Potential of Soils Utilizing In-situ Testing” M.Sc Thesis