分段变速加载对含瓦斯突出煤力学特性影响试验研究

Experimental study on influence of piecewise variable speed loading on mechanical properties of outburst coal containing gas

为探究采动应力变化对含瓦斯突出煤力学特性的影响,利用RLW-500G煤岩三轴蠕变-渗流试验系统,对新景矿含瓦斯突出煤进行了不同围压和瓦斯压力下的常规三轴和分段变速加载力学试验。结果表明:煤样在2种应力路径下的全应力应变曲线均可分为压密、线弹性、塑性变形、应力跌落和残余应力5个阶段;随着围压的升高或者瓦斯压力的降低,煤体在2种应力路径下的强度和弹性模量均增大;相较于常规三轴,煤体在分段变速加载路径下的强度普遍增大,峰值轴向应变、峰值环向应变绝对值和峰值体积应变绝对值也普遍增大,失稳破坏瞬间应力跌落和能量释放更加剧烈。Mohr-Coulomb强度准则仍然适用于分段变速加载条件下的含瓦斯突出煤,该研究对于认识煤与瓦斯突出的发生机制具有一定的指导意义。

In order to explore the influence of the changing mining stress on the mechanical properties of outburst coal containing gas,the mechanical tests of conventional triaxial loading and piecewise variable speed loading on the outburst coal containing gas in Xinjing mine under different confining pressures and gas pressures were carried out by using RLW-500G coal and rock triaxial creepage-seepage test system.The results showed that the total stress-strain curves of coal samples under two stress paths could be divided into 5 stages:compaction,linear elasticity,plastic deformation,stress drop and residual stress.With the increase of confining pressure or the decrease of gas pressure,both the strength and elastic modulus of the coal body increased under two stress paths.Compared with the conventional triaxial loading,the strength of coal body under the path of piecewise variable speed loading increased generally,the peak axial strain,absolute value of peak circumferential strain and absolute value of peak volume strain also increased generally,and the stress drop and energy release were more drastic on the moment of instability failure.The Mohr-Coulomb strength criterion was still applicable to the outburst coal containing gas under the conditions of piecewise variable speed loading.The study has a certain guiding significance for understanding the occurrence mechanism of coal and gas outburst.