Anisotropic Deformation Model for Hawkesbury Sandstone Incorporating Inherent Mobilised Shear Strength

Noorfaizah Hamzah,Nur Ain Mat Yusof,Mohd Jamaludin Md Noor

doi:10.13189/cea.2021.091311

Abstract

An extensive study on modelling progressive Hawkesbury Sandstone degradation by anisotropic deformation subjected to monotonic loadings is presented and discussed in this study. Hawkesbury Sandstone was used due to its unique behaviour, which was initially assumed to be a uniform testing lithology with respect to grain size, compressive strength and stiffness. This study identified a theoretical approach to the anisotropic model of rock deformation. The model utilizes the stress-strain curve to derive the development of mobilised shear strength and applies it to the rock to simulate how it compresses in anisotropic. Monotonic loading tests were performed in triaxial conditions at variations of confining pressure, 4MPa and 8MPa. An increment of confining pressure was used to obtain elevation in the stress-strain curve. Progressive monotonic loading changed the mechanical characteristics of the rock; the level of the applied stress is compressed axially and then expanded laterally. During applied loading, the rock may experience damage or rock failure; the correlation between the magnitude of the mobilised shear strength and the axial stress associated with it is regarded as an intrinsic property in the rock mass. The stress-strain behaviour of rocks under anisotropic stress conditions can be predicted using this method. The mobilised minimum friction angle is used to determine the location of the mobilised shear strength envelope. The results reveal that the mobilised intrinsic shear strength is developed if the rock is forced to compaction. This is evidenced by the envelope rotating upward to the shear force envelopes during failing. Consequently, it can be deduced that the cementation (c') of the rock increases.

Highlights

Rocks can be a challenge as they included different types of inhomogeneities and discontinuities
More emphasis is placed on rock behaviour that is subject to loading under varying loading conditions, in various stress-strain rates and pattern of behaviour that emerges after rock failure
The deformation of evaporating sedimentary rock under cyclic loading needs further studies, which were based on their findings, during monotonic stress, the peak strengths of their rock samples decreased to varying degrees under cyclic loading. [1]

Summary

Introduction

Rocks can be a challenge as they included different types of inhomogeneities and discontinuities. Due to the fact that the intrinsic attributes of the rock are founded through loading, the rock may fail when it reaches the monotonic failure stress. The deformation of evaporating sedimentary rock under cyclic loading needs further studies, which were based on their findings, during monotonic stress, the peak strengths of their rock samples decreased to varying degrees under cyclic loading. The damage or failure of faulted rock slope is a quite difficult problem in geotechnical engineering, and attention has been drawn from researchers for a long time Under static loadings such as gravity or engineering building, the rock material within a certain zone behind the tip of a crack/fault will behave strain-softening property due to the action of stress erosion or chemical erosion. The significance of obtaining the peak strength of rocks and the complete stress-strain curve of rocks through laboratory testing has been acknowledged, as this could have an impact on the structural stability and strength of the rock [7]

Specimen Preparation

Experimental Setup and Procedure

Monotonic Compressive Loading

Results and Analysis

Conclusions