Experimental study on mechanical characteristics of unloaded damaged white sandstone before peak
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ORIGINAL PAPER
Experimental study on mechanical characteristics of unloaded damaged white sandstone before peak Heng Ren 1 & Yongjian Zhu 1,2 & Ping Wang 1,2,3,4 & Weijian Yu 1,2 & Peng Li 1 & Yuqun Zhang 1 Received: 12 November 2019 / Accepted: 13 August 2020 # Saudi Society for Geosciences 2020
Abstract In order to study the problem of deformation and failure caused by rock unloading during excavation and mining, a three-axis loading-unloading-uniaxial reloading mechanics with different confining pressures and different initial axial pressures was applied to white sandstone specimens with the RMT-150 testing machine characteristic test. The damage and weakening mechanisms of white sandstone specimens during triaxial loading, unloading, and uniaxial reloading were analyzed. The experimental results show that the peak strength of the specimen has a linear relationship with the confining pressure. The greater the confining pressure, the higher the peak strength of the white sandstone specimen. The peak strength of the specimen and the initial axial compression load ratio (the ratio of the initial axial compression to the triaxial peak load intensity) and the porosity have a 3rd-order polynomial relationship. The damage and weakening of the strength of the rock specimen are related to the load history. The greater the initial axial pressure, the faster the reloaded specimen from the crack closure to the elastic deformation under steady-state damage to the accelerated elastic-plastic deformation under accelerated damage, and the smaller the peak load strength after unloading the specimen. In addition, combined with the loading history of rock, a strength weakening calculation method based on the loading process state is proposed. After verification, this method is feasible. Keywords Excavation unloading . Three-axis loading-unloading-single-axis reloading . Initial axial load ratio . Damage weakening
Responsible Editor: Domenico M. Doronzo Innovation of this research in the text (1) Researched the laboratory loading-unloading path that better reflects the unloading of roadway excavation. (2) The influencing factors of rock peak strength are studied, and the mathematical expression is obtained by combining the experimental data. (3) Combining the history process of rock loading, a calculation method of strength weakening based on the state of loading process is proposed. After verification, this method is feasible. * Heng Ren [email protected] * Yongjian Zhu [email protected] 1
School of Resource & Environment and Safety Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
2
Work Safety Key Lab on Prevention and Control of Gas and Roof Disasters for Southern Goal Mines, Hunan University of Science and Technology, Xiangtan 411201, Hunan, China
3
Hunan Provincial Key Laboratory of Safe Mining Techniques of Coal Mines, Hunan University of Science and Technology, Xiangtan 411201, Hunan, China
4
Hunan Province Key Laboratory of Coal Resources Clean-utilization and Mine Environment Prote
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