Study on the influence of fill aspect ratio and internal friction angle on the active sliding surface of finite soil behind rigid walls

Abstract

The failure mode of soil with limited width behind a rigid retaining wall differs from the classical Coulomb theory. Position and form of the slip surface are crucial factors affecting the calculation of earth pressure. This study investigates the active failure modes of limited soil to provide basis for the theoretical research on active earth pressure. Taking the TT mode as an example, the study uses a self-made model to conduct active failure tests on cohesion soil. The digital image method is employed to collect and analyze the soil images during the testing process, and the result are compared with numerical simulation result to study the of the active slip surface in limited soil. The result show that the active failure slip surface in limited soil is a “broken line” passing through heel of the wall, and the slip surface is closely related to the width-to-height ratio and the internal friction angle. The result indicate that:(1) The smaller the width-to-height ratio, the more segments the slip surface has, the larger the initial rupture angle of the soil, and the steeper slip surface becomes. The critical width-to-height ratio for limited soil is 0.49.(2) The smaller the internal friction angle, the more the slip surface has, and the smaller the rupture angle of the slip surface. The critical internal friction angle for limited soil is slightly greater than 43.1°.(3) The active earth pressure in limited soil is generated by the “triangular” sliding mass on the left side of the slip surface, which less than the earth pressure of the trapezoidal sliding wedge in Coulomb's theory. The width-to-height ratio and the internal friction angle of the fill are important factors affecting the failure mode of limited soil, and they are indispensable considerations for determining whether the soil behind the wall is in a limited or semi-infinite.

Keywords

limited soil / model test / numerical simulation / active failure / slip surface