不同加载速率下煤体强度与破碎特征实验研究

Experimental study on coal mass strength and fragmentation characteristics under different loading rates

通过AG-Ⅰ250 kN万能实验机对滇东矿区煤体试件进行单轴压缩实验,探讨了突出危险煤体在不同荷载速率环境下的强度特性与破碎特征。结果表明:煤体应力—应变曲线经历线弹性、塑性、峰后破坏3个阶段,弹性特征随加载速率的增加愈发明显;随着加载速率的增加,煤体峰值应变增大,弹性模量与加载速率呈线性关系;煤体在单轴压缩条件下的破坏形式多表现为脆性破坏,随着加载速率的增加,破碎煤样的折算直径减小,新增表面积增大,整体破碎程度随加载速率的增加而增大,与宏观煤体破坏剧烈程度吻合;不同加载速率下煤体强度特征符合Coulomb准则,峰值强度与达到破坏时间与加载速率呈线性关系。

The uniaxial compression test of coal mass samples taken from Yuwang Coal Mine in eastern Yunnan mining area was carried out by Shimazu AG-Ⅰ250 kN universal testing machine to investigate the strength characteristics and crushing characteristics of protruding dangerous coal mass samples under different loading rates.The test results show that the stress and strain curves of coal mass goes through three stages:linear elasticity,plasticity and post-peak failure,and the elastic characteristics become more and more obvious with the increase of loading rate.With the increase of loading rate,the peak strain of the coal mass increases,and the elastic modulus has a linear relationship with the loading rate.The failure mode of coal mass under uniaxial compression is often manifested brittle failure,with the increase of loading rate,the converted diameter of crushed coal sample decreases and the newly added surface area increases,the overall degree of fracture increases with the increase of loading rate,which is consistent with the macroscopic degree of coal mass failure.The strength characteristics of coal mass at different loading rates meet Coulomb criterion,and the peak strength and the time to reach the failure have a linear relationship with the loading rate.