动静载作用下房柱式采空区煤柱失稳时间预测研究

Prediction of coal pillar instability time in room-pillar goaf under dynamic and static load

针对动静载作用下大面积房柱式采空区失稳时间难以预测的问题,以鄂尔多斯市敬老院煤矿为研究背景,通过室内循环加卸载与单轴加载试验对比分析了煤柱在动载与静载作用下力学承载特征。选取开尔文体模型,基于蠕变理论,结合顶板-煤柱系统力学模型,得出了房柱式采空区煤柱保持稳定的最小时间函数表达式。考虑时间因素,通过施加循环加卸载荷模拟动静载作用方式,建立了房柱式采空区数值模型,研究了动静载作用下房柱式采空区煤柱随时间失稳的动态演化过程。研究结果表明:煤样在循环加卸载作用下比在固定载荷作用下的极限破坏强度偏低;煤柱在蠕变作用下的有效承载时间与煤柱横截面积的对数正相关,与煤柱的高度和顶板刚度的对数负相关;将煤柱的破坏过程分为稳定阶段、发育阶段和失稳阶段。通过理论模型、数值模拟及现场实测,验证了煤柱有效承载函数的可靠性。

Aiming at the problem that it is difficult to predict the instability time of large area house-pillar goaf under dynamic and static load,taking the Jinglaoyuan Coal Mine in Ordos City as the research background,the mechanical bearing characteristics of coal pillar under dynamic and static load are analyzed through indoor cyclic loading and unloading tests and uniaxial loading tests.Based on the creep theory and combined with the stress model of roof pillar system,the effective bearing time function of coal pillar in room pillar goaf is deduced.Considering the time factor,a numerical model is established to simulate the action mode of dynamic and static load by applying cyclic loading and unloading load,and the dynamic evolution process of coal pillar instability with time under dynamic and static load is studied.The results show that the ultimate failure strength of coal samples under cyclic loading and unloading is lower than that under fixed load.The effective bearing time of coal pillar under creep is log-positively correlated with the cross-sectional area of coal pillar,and log-negatively correlated with the height of coal pillar and the stiffness of roof.The instability process of coal pillar can be divided into three stages:stability stage,development stage and instability stage.The reliability of effective load function of coal pillar is verified by theoretical model,numerical simulation and field measurement.