ABSTRACT:

Analysis and interpretation of flow and instability of sloping soil masses due to rainfall are made using triaxial compression test results. In this study, anisotropically consolidated undrained triaxial compression tests are carried out on two soils, Omigawa silty sand and Jamuna river silty sand. The degree of anisotropic consolidation is defined by Kc = s3c''/s1c'', where s3c'' and s1c'' are the lateral and axial stresses achieved after consolidation, respectively. The flow characteristics of the soils are examined in several manners in terms of contractive and dilative behaviours, with respect to the consolidation line, steady state line, phase transformation line and initial dividing line. The residual strength is evaluated with respect to the initial state ratio. Finally, the method for the evaluation of flow susceptibility of sloping soil masses is discussed within the context of the interpreted test results.

INTRODUCTION

In the past literature, one of the notable developments for the analysis and interpretation of flow failures of sloping soil masses may be found in the concept of "drained initiation" and "undrained mobilization", (Anderson and Sitar, 1995). The mean effective stress further reduces mainly due to seepage flow and the stress states of the soil masses critically approach the failure conditions, which is called a drained initiation, whereby sufficiently greater strains are induced within the soil masses to cause undrained mobilization of the entire soil masses. To examine the behaviour and flow of saturated soils within this context, constant shear drained triaxial tests and anisotropically consolidated undrained triaxial compression tests were performed by several researchers including Anderson and Sitar (1995), Zhu and Anderson (1998) and Tsukamoto et al. (1998). In this study, anisotropically consolidated undrained triaxial compression tests are carried out on two soils, and the test results are interpreted to examine the flow characteristics of each soil.

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