Unstable behaviour of sand and its implication for slope instability

TLDR

The study proposes a new framework for analysing the instability of granular soil slopes using the critical state line and a modified state parameter. The authors developed and applied this framework to examine test data and determine instability conditions for both contractive and dilative granular soil slopes under varying shear stress levels. Constant shear‑drained tests on loose and dense sand revealed instability lines that vary with void ratio, as established by the new framework. Keywords: deformation, laboratory tests, liquefaction, sands, shear strength, slope stability.

Abstract

Results of some constant shear-drained (CSD) tests conducted on both loose and dense sand are presented. Using the critical state line and a modified state parameter, a new framework for analysing the instability of granular soil slopes is proposed. The test data were examined and interpreted using the new framework. Instability lines for sand with different void ratios were established within this framework. The conditions for the occurrence of instability in both contractive and dilative granular soil slopes under various shear stress levels were examined using the proposed framework.Key words: deformation, laboratory tests, liquefaction, sands, shear strength, slope stability.