Modelling of Static Liquefaction of Partially Saturated Non-Cohesive Soils

Waldemar Świdziński,Marcin Smyczyński

doi:10.3390/app12042076

Waldemar Świdziński, Marcin Smyczyński

Open Access

https://doi.org/10.3390/app12042076

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Abstract

Static soil liquefaction is widely known to be a serious danger to the stability of structures. The phenomena governing pore water generation, which leads to liquefaction in fully saturated soils, are already quite well described. However, much less is known of these phenomena occurring in partially saturated porous media, although this, too, is an important issue in geotechnics. This study presents the application of a semi-empirical model to predict the response of partially saturated soils under undrained conditions. The model proposed is based on an incremental equation describing the pre-failure undrained response of partially saturated non-cohesive soils during monotonic shearing in a standard triaxial test. Improved differential equations taking into account pore fluid compressibility were implemented together with empirical coefficients describing soil skeleton compressibility during the unloading phase. Model coefficients were determined in triaxial compression tests. The influence of the saturation level represented by Skempton’s parameter B on the full spectrum of predicted stress paths was shown. For the analyzed saturation range, the maximum stress deviator normalized by initial mean effective stress varied from 0.38 to 1.67 for B values between 0.93 and 0.29, respectively. Model predictions were confronted with the results of triaxial tests for two types of non-cohesive soils (quartz medium sand and copper ore post-flotation industrial tailings). Good agreement between experimental data and theoretical predictions was achieved.

Highlights

It is well known that monotonically loaded non-cohesive saturated soils under undrained conditions may be prone to liquefaction due to a static [1] or cyclic [2,3] load
Changes in pore pressure, normalized by initial mean effective stress in relation to vertical strain ε1 are shown in Figure 9 for Skarpa sand and in Figure 10 for OZM50 tailings, respectively
It can be seen that generated excess pore pressure increased with saturation and led to the liquefaction of samples with the highest saturation level

Summary

Introduction

It is well known that monotonically loaded non-cohesive saturated soils under undrained conditions may be prone to liquefaction due to a static [1] or cyclic [2,3] load. It was originally thought that, in order for soil to liquefy, voids should be completely filled with water which corresponds to full saturation of the medium. This was due to the fact that any presence of air would significantly limit or prevent the process of pore pressure build-up. Such an approach was physically justified because the presence of air results in full or partial dissipation of the pore pressure excess and scales it down by the Skempton’s parameter B decreasing liquefaction potential [4]. There followed many others related to the same issue, e.g., [7,8,9,10,11,12,13]

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