地应力场中煤岩卸围压过程力学特性试验研究及瓦斯渗透特性分析

应用MTS815力学试验机,对典型煤与瓦斯突出矿井松藻矿务局打通一矿突出煤层原煤制备的型煤试件进行型卸围压试验研究。研究结果表明:(1)位移控制方式卸围压将导致试件的扩容损伤,力控制方式卸围压将导致试件的破坏。(2)用位移控制卸围压时,在某一初始围压下,试件的轴向应力随围压的降低而减小,轴压减小的速率越来越大,屈服阶段卸围压曲线比弹性阶段卸围压曲线更加非线性;随初始围压的加大,屈服阶段卸围压曲线的非线形特征更加明显。(3)用力控制方式卸围压时,在某一初始围压下,试件的轴向应变随围压的降低而增大,轴向应变增大的速率越来越大,屈服阶段卸围压时轴向应变的增大比弹性阶段卸围压时更为迅速;随初始围压的增大,屈服阶段卸围压时试件加速破坏的趋势更加明显;通过轴向应变可计算分析卸围压过程中试验机对试件作的功。根据试验结果,结合全应力-应变过程煤岩瓦斯渗透特性的试验结果,推导出卸围压过程瓦斯渗透特性曲线。根据以上结果,应用损伤理论和Mohr-Coulomb强度理论推导含瓦斯煤岩卸围压过程中试件的损伤和强度的计算公式。研究结果对预测预报瓦斯涌出和预测卸围压过程中煤岩的破坏具有现实指导意义。

EXPERIMENTAL STUDY OF MECHANICAL CHARACTERISTICS OF COAL SPECIMEN IN PROCESS OF UNLOADING CONFINING PRESSURE IN GEOSTRESS FIELD AND ANALYSIS OF GAS SEEPAGE CHARACTERISTICS

Based on the briquette specimens of the outburst coal seam of typical coal and gas outburst mine of Datong in Songzao，the experimental study of unloading confining pressure of briquette specimen is performed by means of mechanical testing machine MTS815. The results are shown as follows：(1) unloading confining pressure with displacement control leads to the dilatancy and damage of briquette specimens，unloading confining pressure with load control leads to the failure of briquette specimens；(2) if the confining pressure is unloaded by means of displacement control，within a certain range of initial confining pressure，the axial stress of briquette specimens drops with decreasing confining pressure，and the velocity of axial stress drop rises，the nonlinearity of curve of unloading confining pressure is more significant when unloading confining pressure in yield phase than that in elastic phase；the nonlinearity is more and more obvious with the increase in initial confining pressure；(3) if the confining pressure is unloaded by means of load control，within a certain range of initial confining pressure，the axial strain of briquette specimens rises with decreasing confining pressure，the velocity of axial strain rise increases，the increase in axial strain is more significant when unloading confining pressure in yield phase than that in elastic phase. The increasing failure is more and more obvious in yield phase with the increase in initial confining pressure；the work of testing machine done in the process of unloading confining pressure can be calculated and analyzed according to axial strain. Based on the test results，combining with the test results of permeability of briquette specimens in the complete stress-strain process，the permeability curve of briquette specimens in the process of unloading confining pressure is deduced. Based on these results，using damage theory and Mohr-Coulomb theory，the formula for calculating the damage of briquette specimens containing gas in the process of unloading confining pressure is derived. The study results have a reference value for predicting gas emission and failure in the process of unloading confining pressure.