加载与卸载过程瓦斯抽采钻孔变形特征

抽采钻孔的稳定性影响到抽采工程效果的好坏。工作面回采过程中,由于支承压力随工作面推进的移动,采动影响范围内的抽采钻孔受到加载、卸载应力的作用。为得到加卸载条件下抽采钻孔变形及破坏规律,采用数值模拟的方法对不同应力变化速率下钻孔的破坏进行了计算,共设计10种计算方案,得到了不同加卸载应力变化速率下的钻孔塑性区分布范围及孔壁位移曲线。同时依据数值计算得到的卸载应力变化速率与孔壁变形相互关系,建立了考虑卸载应力变化速率的钻孔周边切应力计算模型。研究结果表明:加载过程中,加载速率对钻孔周边的破坏范围及孔壁位移不产生影响;卸载过程中,钻孔周边破坏范围与初始卸载应力及卸载速率相关,在进行抽采钻孔布置时需综合考虑钻孔的受载力学特征。

Deformation characteristics of gas drainage borehole in loading and unloading

The stability of gas drainage borehole affects the quality of extraction engineering.In the process of mining，the abutment moves along with the advance of the working face，and loading and unloading stresses act on the borehole in mining influence area.In order to obtain the deformation and failure law of the borehole under the condition of loading-unloading，the authors used a numerical method to calculate the failure of boreholes at different stress change rates.Based on ten calculation schemes，the drilling plastic zone distribution and the hole wall displacement curve under different loading and unloading stress changing rates were obtained.At the same time，according to the relationship between the rate of unloading stress and the deformation of the hole wall was obtained by numerical calculation.The calculation model of shear stress around the borehole was established，which considered the rate of unloading stress change.Research indicates that the loading process，loading rate do not affect the extent of damage surrounding borehole and hole wall displacement.The unloading process around borehole damage range is associated with the initial unloading stress and unloading rate.In the drilling arrangement the stress characteristics of boreholes should be considered.