基于煤岩体风化剥离的柱式采空区长期稳定性评价方法研究

The closed partially-extracted mines occupy a large amount of land resources, underground space resources and residual coal resources. The long-term collapsibility of these partially-extracted mines and the harmfulness of mine collapse have seriously threatened the safety of buildings and infrastructures on the ground surface in our country, together with the safe exploitation and utilization of these resources in the future. It is of great significance for the sustainable development of resource-based cities to study the long-term stability evaluation method of closed partially-extracted mines. The groundwater gushed into goafs when the mines were closed, thus the coal-rock mass in the goafs fractured and peeled under the effects of hydro-chemical weathering and strata stresses. It is difficult to accurately evaluate the long-term stability of coal pillars with present stability evaluation methods, as these methods seldom considered the coal-rock debris that peel from the pillar and the roof during weathering and peeling process. The peeled coal-rock debris backfill the goaf and can provide lateral constraint to the coal pillars, neglecting which would make it hard to estimate the ultimate limit of weathering and peeling damages. To solve this problem, this project prepares to study the laws of coal-rock mass peeling, the properties of peeled coal-rock debris pile and the effect of groundwater inrush on long-term strength of coal-rock mass; and further to reveal the coupling interaction among the groundwater, the peeled coal-rock debris pile and the coal pillar so that a coal-rock mass model can be established based on the long-term strengths and size variations of these coal-rock masses. Finally, a long-term stability evaluation method of partially-extracted mines based on the long-term weathered strength of coal-rock mass and the lateral constraint of coal-rock debris pile will be proposed, providing theoretical and technical supports for collapse disaster control of closed partially-extracted mines, and also for the safe exploitation and utilization of residual mine resources in the future.

关闭矿井柱式采空区占压大量地表土地资源、地下空间资源和残余煤炭资源，其塌陷又具有突陷性、长期性、危害性，已严重威胁我国地表建、构筑物安全以及未来柱式采空区资源的安全开发利用。研究关闭矿井柱式采空区长期稳定性评价方法对资源型城市可持续发展具有重要意义。矿井关闭后地下水涌入采空区，煤岩体在水化学风化、应力等因素影响下剥离破坏。现有柱式采空区稳定性评价理论未充分考虑煤岩体剥离及剥离煤岩碎块对采空区的充填作用和对煤柱的约束作用，难以准确评价煤柱长期稳定性，针对这一问题，本项目拟在研究煤岩体剥离破坏规律、剥离煤岩体堆积体特性、地下水对煤岩体长期强度影响的基础上，明确地下水-剥离堆积体-煤柱协同作用关系，建立煤岩体长时强度、尺寸变化模型，构建基于煤岩体长期风化强度和剥离体约束下的煤柱长期稳定性评价方法，为关闭矿井柱式采空区塌陷灾害防控及未来柱式采空区资源安全开发利用提供基础性理论和技术支持。

柱式开采能够有效减小地表沉降，降低采矿活动对地质环境的扰动，是绿色开采的重要组成部分。然而矿柱失稳会使采区覆岩应力重新分布，进而可能造成群柱失稳、地表大范围突陷等问题。煤岩体长期强度及其失稳破坏的后区特征是影响采区长期稳定性的两个关键因素，但当前的研究大多忽略了后者的作用。矿柱及顶底板煤岩破坏过程中产生的煤岩碎块将作为充填体堆积在采区，在一定程度上可抑制煤岩持续破坏。为此，项目拟协同考虑水化学风化煤岩体的长期强度与煤岩的剥离破坏特征，研究柱式采区长期失稳机理及灾变规律，构建柱式采空区长期稳定性评价方法。主要开展了以下工作：（1）全面研究和梳理了以长壁、柱式、露天开采为代表的各类采空区的地质环境灾变机理，针对多灾耦合问题，以多学科交叉视角提出“采动灾害链网”概念，为灾害链网监测治理及地质环境综合保护提出建议；（2）研究了山区地形条件下柱式采空区矿柱应力分布特征及应力集中机理，研究发现，坡顶至坡底扩展压力拱形态的突变是造成覆岩荷载传输中断、矿柱应力集中的根本原因；提出了山区地形下矿柱应力计算方法；（3）制作加工了468例煤岩试样，开展了煤岩水化学风化实验；（4）合作研究了地表位移稳定性监测与预测方法，基于SAR pixel offset tracking和改进概率积分法，以及SBAS InSAR和LSTM神经网络模型，合作提出了两个地表移动预计模型；（5）探索了视频深度学习与煤岩破坏识别技术。