Strain energy evolution and damage characteristics of deep clay under different stress rates

Abstract

Deformation and failure of deep clay samples are closely related to energy changes. Investigating the energy conversion and damage behavior of deep clay during loading and unloading tests has important significance for prevention-control of soil destabilization damage caused by mine shaft excavation. In the present work, triaxial tests of consolidated clay under different stress paths and stress rates were conducted. The results reveal that the mechanical properties of soils have strong stress rate effects and the samples mainly experience energy storage in the elastic stage, after that, the energy conversion mainly undergoes an increase of dissipative energy and release of elastic energy, which is also confirmed by the results of the analysis in the subsequent CT tests. Two damage indicators were compared, finding that the indicator based on dissipative energy has more obvious differences in two stress paths and can be used as a better indicator to describe the damage evolution of soils. Finally, in the triaxial shear test, due to the unloading effect of confining pressure, the damage of soils increased more rapidly near breaking than in the triaxial compression test, which indicates that the damage caused by unloading on deep soil is more abrupt than that caused by loading.

Keywords

deep clay / damage evolution / computer tomography (CT) / triaxial testing

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