Nonlinear Viscoelastic–Plastic Creep Model Based on Coal Multistage Creep Tests and Experimental Validation

Junxiang Zhang,Bo Li,Peng Li,Conghui Zhang

doi:10.3390/en12183468

Junxiang Zhang, Bo Li + Show 2 more

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https://doi.org/10.3390/en12183468

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Abstract

The development of fractures, which determine the complexity of coal creep characteristics, is the main physical property of coal relative to other rocks. This study conducted a series of multistage creep tests to investigate the creep behavior of coal under different stress levels. A negative elastic modulus and a non-Newtonian component were introduced into the classical Nishihara model based on the theoretical analysis of the experimental results to propose a nonlinear viscoelastic–plastic creep model for describing the non-decay creep behavior of coal. The validity of the model was verified by experimental data. The results show that this improved model can preferably exhibit decelerating, steady state, and accelerating creep behavior during the non-decay creep process. The fitting accuracy of the improved model was significantly higher than that of the classical Nishihara model. Given that acceleration creep is a critical stage in predicting the instability and failure of coal, its successful description using this improved model is crucial for the prevention and control of coal dynamic disasters.

Highlights

With the gradual depletion of mineral resources in the shallow, most mines begin the trend of deep mining [1,2]
The creep test The results show that the coal of creep characteristics different
This study aims at developing a nonlinear model to describe the viscoelastic–plastic creep behavior of coal

Summary

Introduction

With the gradual depletion of mineral resources in the shallow, most mines begin the trend of deep mining [1,2]. The rheological characteristics of coal become more significant with the increase in strata stress, thereby decreasing its mechanical strength under long-term static load, which causes deep mining to face many time-related problems [3,4], such as aggravated roadway deformation, collapse of gas extraction boreholes, and gas and coal outburst delay [5,6,7] All of these problems pose serious threats to underground safety. ThisThus, time,the theelastic flow rule of energy will gradually decrease as creep deformation develops At this time, the flow rule of coal and coal and rock mass should be similar to that of viscoelastic–plastic flow. A negative elastic rock mass should be similar of viscoelastic–plastic

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Results

Conclusion