Foundation model 1 - 1D an 3D parallel coupled models

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REPORT

REDWIN

DAMPING RATIO FROM LABORATORY TESTS

DOC.NO. 20150014-01-R REV.NO. 0 / 2016-06-02

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Project

Project title: REDWIN

Document title: Damping ratio from laboratory tests Document no.: 20150014-01-R

Date: 2016-06-02 Revision no. /rev. date: 0

Client

Client: Research Council of Norway Client contact person: Harald Rikheim

Contract reference: 243984/E20

for NGI

Project manager: Amir Kaynia Prepared by: Knut H. Andersen Reviewed by: Finn Løvholt

Summary

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NO-0806 Oslo NO-7485 Trondheim [email protected] COMPANY NO. FS 32989/EMS 612006

Norway Norway 958 254 318MVA

p:\2015\00\20150014\leveransedokumenter\rapport\rap1_soil_material_damping\20150014-01-r_final_report on soil damping.docx

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Summary continued

Document no.: 20150014-01-R Date: 2016-06-02

Rev.no.: 0 Page: 5

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Rev.no.: 0 Page: 7

Review and reference page

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1 Introduction

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2 Definition of damping ratio, D

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Figure 2.1 Principle sketch of a simplified stress-strain loop during pure cyclic loading. The stress and strain are denoted by ʏĂŶĚ J respectively. Maximum stress and strain values are denoted by the "m" subscripts.

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Figure 2.2 Stress strain curves from cyclic DSS test on high plasticity clay with symmetrical cyclic loading

Figure 2.3 Stress strain curves from cyclic DSS test on high plasticity clay with non-symmetrical cyclic loading

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Figure 2.4 Stress strain curves from cyclic DSS test on dense sand with

symmetrical cyclic loading

Figure 2.5 Stress strain curves from cyclic triaxial test on dense sand with non-symmetrical cyclic loading

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Figure 2.6 Calculation of damping ratio in dense sand with symmetrical cyclic loading

Figure 2.7 Calculation of damping ratio in dense sand with non-symmetrical cyclic loading

3 Soil types

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w the water content, and OCR the overconsolidation ratio Name Ip (%) St % clay w (%) OCR Test

types Parameters High plasticity

clay 75-84 2.3 65-75 77-86 1.35 Triaxial &

DSS

Intact &

remolded T=10 & 100s Medium

plasticity clay 37 5.5 45 ~50 1.45 Res. col. Intact Low plasticity

clay 17-20 2-3 22-37 15-23 1.45 DSS

Res. col.

Intact T=10s Quick clay 8-11 75-100 36-38 35 1.5 DSS Intact

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Table 3.2 Sand characteristics and test types. Dr denotes the relative density, and V^vc' the effective vertical stress

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%

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wafter

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Bank A 0 <1 0.017

Triaxial &

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undrained 'Wa

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Bank B <1 20 0.087 ~100 ~17.7 1 200 Wcy=0.06Vvc'

~80 ~20 1 200 Wcy=0.06Vvc'

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Rev.no.: 0 Page: 13

4 Damping ratio for clays

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p:\2015\00\20150014\leveransedokumenter\rapport\rap1_soil_material_damping\20150014‐01‐r_final_report on soil damping.docx

Document no.: 20150014‐01‐R Date: 2016‐06‐02

Rev.no.: 0 Page: 15

4.2 Damping ratio in triaxial tests on high plasticity clay

The damping ratio in cyclic triaxial tests with different average shear stress, a, on high plasticity clay is shown in Figure 4.7. The samples were consolidated with a K0'=0.55, corresponding to a=0=0.45su. The change in average shear stress a=a-0 was applied under undrained conditions.

The results show that D vs. cy is relatively independent of N for a=0=0.45su. For other values of a, however, D is a function of both a and N. D drops markedly from N=1 to 2, and continues to drop during the next ~3 to 10 cycles before it becomes constant or starts to increase. One exception is one of the tests with a=0=0.45s^u, which does not start to increase with N.

D is close to the lower Seed-Idriss (1970) curve for high N, but generally higher than the lower Seed-Idriss (1970) curve for low N.

4.2.1 Effect of load period on damping ratio in triaxial tests on high plasticity clay

The results from four triaxial tests with T=100s load period are compared to the results from four triaxial tests with 10s load period in Figure 4.8. The curves for tests with T=100s are dotted. The tests are run on the high plasticity clay and with different average shear stresses, as explained in Section 4.3. The comparison shows that there is a tendency for D to increase with increasing load period, as for the DSS tests (Section 4.3).

4.3 Comparison of damping ratio in DSS and triaxial tests on high plasticity clay

The damping ratio measured in DSS and triaxial tests on high plasticity clay is compared in Figures 4.9, 4.10 and 4.11.

The results show that

 DSS with a=0 tend to give the lowest D for given values of cy and N.

 triaxial tests give higher D than DSS tests in tests consolidated to the in situ stress conditions (a=0=0.45su in triaxial tests and a=0 in DSS tests) (Figure 4.10).

 the results from tests with T=100s (Figure 4.11) confirm the results measured in tests with 10s (Figures 4.9 and 4.11).

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Figure 4.1 Damping ratio as function of cyclic shear strain in DSS tests on 3 different clays. Symmetrical cyclic loading.

Figure 4.2 Effect of average shear stress on damping ratio in DSS tests on high plasticity clay.

Figure 4.3a Effect of average shear stress on damping ratio in DSS tests on quick clay. T=10s

Figure 4.3b Effect of average shear stress on damping ratio in DSS tests on quick clay. T=1s

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Rev.no.: 0 Page: 17

Figure 4.4 Effect of remoulding on damping ratio in DSS tests on high

plasticity clay

Figure 4.5 Effect of load period on damping ratio in DSS tests on high plasticity clay

Figure 4.6 Effect of load period on damping ratio in DSS tests on quick clay

Figure 4.7 Effect of average shear stress on damping ratio in triaxial tests on high plasticity clay

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Figure 4.8 Effect of load period on damping ratio in triaxial tests on high plasticity clay

Figure 4.9 Comparison of damping ratio in DSS and triaxial tests on high

plasticity clay

Figure 4.10 Comparison of damping ratio in

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Figure 4.11 Comparison of damping ratio in DSS and triaxial tests with T=100s on high plasticity clay

Damping ratio, D (%)

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Rev.no.: 0 Page: 19

5 Damping ratio for sands

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Figure 5.1 Damping ratio as function of

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Figure 5.2 Damping ratio as function of cyclic shear strain in DSS tests on clean sand with Dr=80%.

Figure 5.3 Comparison of damping ratio in DSS tests on clean sand with Dr=80% and 100%. Symmetrical cyclic loading.

Figure 5.4 Effect of overconsolidation ratio on damping ratio in DSS tests on clean sand with Dr=80%.

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Rev.no.: 0 Page: 25

Figure 5.5 Effect of consolidation stress on damping ratio in DSS tests on clean sand with Dr=100%.

Figure 5.6 Effect of consolidation stress on damping ratio in DSS tests on clean sand with Dr=80%.

Figure 5.7 Effect of consolidation stress on damping ratio in DSS tests on clean sand with Dr=80% and OCR=4. Symmetrical cyclic loading.

Figure 5.8 Effect of precycling on damping ratio in DSS tests on clean sand with Dr=100%. Symmetrical cyclic loading.

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Figure 5.9 Effect of precycling on damping

ratio in DSS tests on clean sand with Dr=80%. Symmetrical cyclic loading.

Figure 5.10 Effect of precycling on damping ratio in DSS tests on clean sand with Dr=80% and OCR=4.

Figure 5.11 Effect of average shear stress on damping ratio in DSS tests on clean sand with Dr=100%.

Figure 5.12 Effect of average shear stress on damping ratio in DSS tests on clean sand with Dr=80%.

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Foundation model 1 - 1D an 3D parallel coupled models

REDWIN

DAMPING RATIO FROM LABORATORY TESTS

Project

Client

for NGI

Summary

Summary continued

Contents

Review and reference page

1 Introduction

2 Definition of damping ratio, D

3 Soil types

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4 Damping ratio for clays

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4.2 Damping ratio in triaxial tests on high plasticity clay

4.3 Comparison of damping ratio in DSS and triaxial tests on high plasticity clay

5 Damping ratio for sands

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