Outline

  • Abstract
  • 1. Introduction
  • 2. Description of the Experiment
  • 3. Numerical Modeling
  • 3.1 Finite Element Model
  • 3.2 Benchmark Cases Sc and Ss
  • 4. Results of Benchmark Case Sc
  • 5. Parametric Study
  • 5.1 Reinforcement Effects of the Scs
  • 5.2 Shear Stress and Strain Distributions
  • 5.2.1 Deformation Behavior
  • 5.2.2 Shear Stress Distributions
  • 5.3 Influence of the Sc Permeability
  • 5.4 Influence of Surface Load in the Sc Zone
  • 6. Conclusions
  • Acknowledgements
  • Notations
  • References

رئوس مطالب

  • چکیده
  • 1. مقدمه
  • 2. شرح آزمایش
  • 3. مدلسازی عددی
  • 3.1 مدل المان محدود
  • 3.2 موارد معیار SC و SS
  • 4. نتایج مورد معیار SC
  • 5. مطالعه پارامتری
  • 5.1 اثرات مسلح‌سازی ستون‌های سنگی
  • 5.2 توزیع تنش و کرنش برشی
  • 5.2.1 رفتار تغییر شکل
  • 5.2.2 توزیع‌های تنش برشی
  • 5.3 تأثیر نفوذپذیری ستون سنگی
  • 5.4 تاثیر بار سطحی در ناحیه SC
  • 6. نتیجه‌گیری
  • نمادگذاری‌ها

Abstract

Installation oF Stone Column (SC) is a promising ground improvement technique to mitigate liquefaction hazards in sand stratum. In this study, a three-dimensional (3D) Finite Element (FE) analysis was used to simulate a centrifuge experiment on the mitigation of silty sand strata liquefaction using SC approach. The predicted response of the silty sand and SC matched the experimental data well. The overall site-stiffening effects due to the installed SCs as well as the distributions of the shear stress and shear stress reductions were evaluated. A parametric study was conducted to investigate the effect of the SC permeability and the surface load at the SC zone on the effectiveness of liquefaction mitigation. The results showed that the SCs behaved in a combined shear and flexure mode. Furthermore, the SCs with permeability exceeding a threshold value can dramatically decrease the liquefaction hazard. On the other hand, larger surface load did not prevent soil liquefaction and produced negligible benefits in stiffening. The present study further enhances the current understanding of the effectiveness of SC remediation approaches in the silty sand.

Keywords: - - - - -

Conclusions

A 3D FE analysis was conducted to simulate a centrifuge experiment on liquefaction mitigation of silty soils using SCs. The effectiveness of SC mitigation was explored by varying several key parameters. The main findings from this study are summarized below.

1.The FE analysis of the calibrated model produced the dominant liquefaction mechanisms of the SC reinforced silty sand stratum and agreed reasonably with the experimental measurements.

2. The SCs in the silty sand deformed in both flexural and shear modes, in contrast to the current design consideration that assumes pure shear deformation in the SC. In addition, the ratio of the improved to unimproved Rrd depended on the vertical and horizontal location.

3. In general, stiffer responses were observed for the SC remediated silty stratum relative to the unimproved stratum. However, full liquefaction in the upper-half silt stratum was not averted.

4. The SCs could substantially retard the build-up of ue throughout silty stratum and significantly reduced the soil acceleration attenuations when the SC permeability is higher a critical value. Likewise, the SC with low permeability did not effectively inhibit the rise in ue in the silty sand, especially near the ground surface, thereby not achieving the benefits for mitigating liquefaction hazard.

5. The stiffening benefit due to the larger load applied at the SC zone was slight but produced attenuation-type acceleration once the stratum was fully liquefied. However, the build-up of ue decreased somewhat with increasing depth.

6. Additional experimental data and parametric studies are needed to explore site-specific liquefaction mitigation strategies with SCs. In addition, a revised design equation should be proposed to estimate the shear stress reduction due to the introduction of the SCs.

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