Anisotropic Constitutive Model of Intermittent Columnar Jointed Rock Masses Based on the Cosserat Theory

Abstract

In this work, an anisotropic constitutive model of hexagonal columnar jointed rock masses is established to describe the distribution law of deformation and the failure of columnar joint caverns under anisotropic conditions, and is implemented to study the columnar jointed rock mass at the dam site of the Baihetan Hydropower Station on the Jinsha River. The model is based on the Cosserat theory and considers the mesoscopic bending effect on the macroscopic mean. The influences of joint plane inclination on equivalent anisotropic elastic parameters are discussed via the introduction of an off-axis transformation matrix and the analysis of an example. It is also pointed out that the six-prism columnar jointed rock mass changes from transverse isotropy to anisotropy under the influence of the angle. A numerical calculation program of the Cosserat constitutive model is developed and is applied to the simulation calculation of a Baihetan diversion tunnel to compare and analyze the respective plastic zones and stress distributions after tunnel excavation under both isotropic and anisotropic conditions. The results reveal that, compared with the isotropic model, the proposed Cosserat anisotropic model better reflects the state of stress and asymmetric distribution of the plastic zone after tunnel excavation, and the actual deformation of the surrounding rock of the tunnel is greater than that calculated by the isotropic method. The results aid in a better understanding of the mechanical properties of rock masses.

Study on Permeability Characteristics of Rocks with Filling Fractures Under Coupled Stress and Seepage Fields

“…Fractured rock is a typical heterogeneous, porous medium whose volume is completely occupied by the fractures and matrix [39,44]:…”

Multiscale Homogenization and Analysis of Anisotropic Assemblies as Cosserat Continua

“…Material porosity can be also considered since it has an important role. It has been demonstrated in the recent literature that the present model is able to analyze fibre-reinforced ceramics, porous ceramic composites or metal-ceramic composites but also geomaterials or jointed rocks (Adhikary and Dyskin, 1997;Adhikary et al, 1999;Li et al, 2009;Lu et al, 2020)) and masonry (Greco et al, 2016b(Greco et al, , 2017Pepe et al, 2019Pepe et al, , 2020.…”

A Case Study on Tunnel Excavation Stability of Columnar Jointed Rock Masses with Different Dip Angles in the Baihetan Diversion Tunnel

“…Physical model tests have the advantages of low production cost and the ability to simulate multiple working conditions that are not limited by engineering realities, making them an important means of studying CJRM. Lu et al [16,17] prepared regular hexagonal CJRM specimens with different dip angles and conducted uniaxial, conventional triaxial, and true triaxial compression tests to study the strength and deformation anisotropy characteristics of CJRM, proposing an anisotropic constitutive model for CJRM anisotropy. Que et al [18][19][20][21][22] proposed a pentagonal cross-section and an irregular cross-section that more realistically simulates the CJRM cross-section, and prepared pentagonal, hexagonal, quadrangular, and irregular cross-section specimens for multi-axial testing, revealing the effects of different cross-sectional shapes on CJRM strength and deformation anisotropy, and proposed a failure strength criterion for CJRM.…”