下分层不同层位千米钻孔稳定性研究

Study of Kilometer Drilling Stability at Different Strata Beneath the Floor

抽采钻孔的稳定性影响到抽采工程效果的好坏.采动作用下,位于底板下方不同层位千米钻孔的加卸载路径不同.为得到采动作用对不同层位钻孔稳定性的影响,分析了底板不同层位钻孔加卸载路径.依据该路径,设计十种数值模拟计算方案,对底板钻孔在不同速率加卸载、变速加卸载两种方式下的破坏范围、孔壁位移进行了分析,得到了加卸载结束后各方案对应的塑性区分布范围及加卸载过程中孔壁位移曲线.依据数值计算得到的卸载速率与形变恢复滞后性的关系,建立了考虑卸载速率变化的钻孔周边切应力计算模型.研究结果表明:加载速率对钻孔周边的破坏范围几乎不产生影响;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,在进行底板顺层抽采钻孔布置时需综合考虑布孔位置处的应力值及卸载速率.

The stability of gas drainage drilling affects the quality of extraction engineering. Under the action of mining,underfloor kilometer drillings distributed at different horizons have different loading and unloading paths. To get the influence of mining on borehole stability,the loading and unloading paths of drillings located at different horizons were analyzed and accordingly the hole destruction area and the wall displacement at different loading and unloading rates and time-varying loading and unloading rates were numerically simulated. Through 10 numerical simulation schemes,the distribution of plastic zones and the loading and unloading displacement curves of the hole wall were obtained. Based on the numerically simulated relationship between the unloading rate and the hole deformation hysteresis,the shear stress calculation model around the borehole was built in view of the unloading rate.The results indicate that,during the loading process,the loading rate hardly inflences the destruction area arround the borehole; during the unloading process,the destruction area arround the borehole is related to the initial unloading stress and the unloading rate. The stress and the unloading rate at the hole location shall be synthetically considered in the placing of bedding boreholes.