Instability of Compacted Residual Soil

Sainulabdeen Mohamed Junaideen,Leslie George Tham,Chack Fan Lee

doi:10.3390/geosciences11100403

Sainulabdeen Mohamed Junaideen, Leslie George Tham + Show 1 more

Open Access

https://doi.org/10.3390/geosciences11100403

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Abstract

Static liquefaction of loose sands has been observed to initiate at stress ratios far less than the steady-state stress ratio. Different collapse surface concepts largely based on undrained triaxial test results have been proposed in the literature to explain the above instability phenomenon of loose sands. Studies of the instability behavior of fill material derived from residual soils remain limited. The present study investigated the instability behavior of a compacted residual soil using the conventional undrained triaxial tests and specially equipped constant shear triaxial tests. The test results were characterized in the p’: q: v space using the current state parameter with respect to the steady-state line for the residual soil. A modified collapse surface that has gradients varying with p’ and v was proposed for the loose residual soil to represent the instability states of undrained loading. Under constant shear stress conditions, the soil can mobilize stress ratios higher than those defined by the modified collapse surface. An instability surface was therefore presented for the instability states reached in static loading. Further, an alternative method of deducing the instability surface from the undrained stress paths was introduced.

Highlights

Liquefaction of loose saturated materials has been observed to initiate at a mobilized stress ratio well below the steady-state stress ratio [1,2,3,4]
This study investigated the instability of a compacted residual soil using isotropically consolidated undrained (ICU) and specially equipped constant shear (CS) triaxial tests on specimens of various densities
Instability states demarcated by the peak states of the undrained triaxial tests varied with specific volume and stress level

Summary

Introduction

Liquefaction of loose saturated materials has been observed to initiate at a mobilized stress ratio well below the steady-state stress ratio [1,2,3,4]. Sasitharan et al [6] approximated the state boundary by a planar envelope passing through the steady-state line They showed that liquefaction could be initiated when the stress paths for loose materials approach the state boundary surface in either drained or undrained loading. Most of the liquefaction failures in slopes are induced by the reduction in effective confining stress whilst shear stress remains nearly constant, as opposed to the failures reproduced by increasing shear stress in conventional triaxial tests. This difference was first noted by Bishop and Henkel [7]

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Discussion

Conclusion