Study on Nonlinear Damage Creep Model for Rocks under Cyclic Loading and Unloading

Liangliang Zhang,Xiaojian Wang,Robert Cerný

doi:10.1155/2021/5512972

Liangliang Zhang, Xiaojian Wang + Show 1 more

Open Access

https://doi.org/10.1155/2021/5512972

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Abstract

To determine the nonlinear creep characteristics of rocks under cyclic loading and unloading conditions, a nonlinear Kelvin model and damage viscoplastic model are proposed. The models are connected in series with a linear elastic body to establish a nonlinear damage creep model. The differential damage constitutive equations of the proposed creep model under one-dimensional and three-dimensional stress states are derived based on the creep mechanics and elasticity theory. The damage and unloading creep equations are then obtained based on the superposition principle, and a simple and feasible method for determining the model parameters is determined. Finally, the step cyclic loading and unloading creep test data for lherzolite and limestone are used to verify the rationality and feasibility of the nonlinear damage creep model. The results show that the theoretical creep curves of the nonlinear damage creep model are consistent with the experimental curves which indicates that the proposed model can not only determine the creep properties of lherzolite and limestone under cyclic loading and unloading but also determine the nonlinear characteristics of rocks in the transient and steady-state creep stages and particularly within the accelerating creep stage.

Highlights

Creep characteristics are intrinsic mechanical properties of rocks, which are significant for the analysis of various rock engineering failure problems, such as dam foundation stability, reservoir subsidence, and tunnel support design [1]
There are hundreds of creep models, which can be classified into three types: empirical [4], component [5], and damage models [6, 7]. e empirical creep model is a mathematical expression established by fitting the test results. e empirical creep equation has the advantages of a simple form and few creep parameters
The model parameters of component models are constant under different stress levels; they cannot reflect the nonlinear characteristics of rocks under cyclic loading and unloading

Summary

Introduction

Creep characteristics are intrinsic mechanical properties of rocks, which are significant for the analysis of various rock engineering failure problems, such as dam foundation stability, reservoir subsidence, and tunnel support design [1]. Is is because the models cannot reflect the creep mechanical mechanism of salt rocks by purely fitting mathematically, and the parameters of the creep model lack physical significance [8, 9]. The model parameters of component models are constant under different stress levels; they cannot reflect the nonlinear characteristics of rocks under cyclic loading and unloading. E damage creep model can determine the deterioration damage effect of rocks during cyclic loading and unloading, and its creep model parameters vary with stress level and time. Is model effectively determines the loading and unloading creep properties of the lherzolite and limestone under different stress levels and favorably represents the nonlinear characteristics of accelerating creep, overcoming the shortcomings of the empirical creep models and the component models A novel nonlinear Kelvin body and viscoplastic damage body are established and are connected in series with the elastic body to obtain a novel nonlinear damage creep model. is model effectively determines the loading and unloading creep properties of the lherzolite and limestone under different stress levels and favorably represents the nonlinear characteristics of accelerating creep, overcoming the shortcomings of the empirical creep models and the component models

Establishment of the Nonlinear Damage Creep Model

Parameters Determination

Findings

Conclusions