Finite element modelling of constant stress drained direct simple shear tests on sand for monotonic loading

Bhowmick, Sudipta (2023) Finite element modelling of constant stress drained direct simple shear tests on sand for monotonic loading. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Updated Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (8MB)

Abstract

Simple shear loading is commonly observed in many practical geotechnical engineering problems, and is considerably different from that applied in commonly used geotechnical laboratory tests, such as direct shear and triaxial tests. The simple shear loading conditions in laboratory specimens could be created in several ways; among them, the direct simple shear (DSS) test is apopularonebecause of simplicity of specimen preparation and testing. However, the interpretation of the test results is challenging because the stress state in the specimens cannot be properly evaluated, as typical DSS apparatus allows the measurement of only normal and shear stresses at the top or bottom surface. DSS tests show some different response in some cases; for example, there is less pronounced strain-softening of dense sand compared to that in triaxial tests. Moreover, empirical equations have been proposed based on experimental results, which might be used to estimate soil parameters such as angle of internal friction. Examining the response of soil elements in DSS specimens using Finite Element Method (FEM), it becomes possible to evaluate the complete behavior observed in the laboratory tests. In the present study, three-dimensional finite element (FE) simulation of DSS test is performed for stacked ring and Cambridge type apparatus. In the simulations, a normal stress is applied and then sheared monotonically by maintaining the same normal stress (constant stress test). Simulations are performed for medium and dense sands using the Mohr–Coulomb and a modified Mohr–Coulomb model that considers post-peak softening, respectively. FE results show that stresses are uniform in the central core of the specimen while considerable stress non-uniformity occurs near the boundaries. The stress state at the failure is neither on the point of stress obliquity nor on the maximum shear stress, which has been considered in some studies to calculate the friction angle. Interface resistance between soil and vertical surface(s) increase the stress ratio compared to smooth interface conditions.

Actions (login required)

View Item