Improved Nonlinear Nishihara Shear Creep Model with Variable Parameters for Rock-Like Materials

Hang Lin,Xiang Fan,Xing Zhang,Yanlin Zhao,Shigui Du,Rui Yong,Yixian Wang

doi:10.1155/2020/7302141

Abstract

Creep property is an important mechanical property of rocks. Given the complexity of rock masses, mechanical parameters change with time in the creep process. In this work, a nonlinear function for describing the time-dependent change of parameters was introduced and an improved variable-parameter nonlinear Nishihara shear creep model of rocks was established. By creating rock-like materials, the mechanical properties of rocks under the shear creep test condition were studied, and the deformation characteristics and long-term shear strength of rocks during creep were analyzed. The material parameters of the model were identified using the creep test results. Comparison of the model’s calculated values and experimental data indicated that the model can describe the creep characteristics of rocks well, thus proving the correctness and rationality of the improved model. During shear creep, the mechanical properties of rocks have an aging effect and show hardening characteristics under low shear stress. Furthermore, according to the fact that Gk of the nonlinear model can characterize the creep deformation resistance, a method to determine the long-term shear strength is proposed.

Highlights

Creep property is an important mechanical property of rocks and the main factor affecting long-term stability of geotechnical engineering [1,2,3,4,5,6,7]
To reveal the mechanism of rock mechanical behavior under shear creep conditions and establish a corresponding shear creep model, this study investigated the shear rheological mechanical characteristics of rocks with plastic-elastic deformation by performing a shear test on a similar sandstone material
Stress is the factor that affects the mechanical properties of rocks with plastic-elastic deformation characteristics, which are different from the characteristics of the microfracture compaction stage completed immediately after loading in most rocks

Summary

Introduction

Creep property is an important mechanical property of rocks and the main factor affecting long-term stability of geotechnical engineering [1,2,3,4,5,6,7]. Us, studying the creep characteristics of rocks is crucial. E creep behavior of rocks can be divided into three stages, namely, attenuated, stable, and accelerated creep. In the initial creep stage, the strain increases with time. In the steady-state creep stage, the strain increases uniformly with time, and the duration of this stage is relatively long. In the accelerated creep stage, the strain rate increases with time, and the rock is destroyed after reaching the critical fracture point. Numerous studies have shown that rocks exhibit typical nonlinear characteristics during creep, in which the accelerated creep stage is the most obvious [4, 11, 12]. Relevant studies have shown that model parameters vary during rock creep and are related to stress, time, temperature, and other factors [17, 18]. Moghadamaab [22] used -constitutive model to describe expansion and short- and longterm damages in the creep process of rock salt and established a numerical model of the rock salt excavation

Methods

Results

Conclusion