松散承压含水层下采煤覆岩结构失稳致灾机理研究

The overburden stratum more prone to intact shear fall when can’t form a stable natural balance arch structure, which can induce the support crushing and water inrush disaster for the special overburden structure and hydrogeology conditions during coal mining under unconsolidated confined aquifer with thin bedrock. By means of comprehensive research method combining M.M.Promojiyfakonov theory, Mohr-Coulomb failure criterion, voussoir beam theory and key stratum theory, through integrated means of theory analysis, similar material simulation, numerical simulation and field measurement, etc. are to be applied to carrying out the following research work: (1) to propose an instability criterion of the overburden structure during coal mining under unconsolidated confined aquifer, the limit equilibrium state of the overburden structure was analyzed by shear band coalescence criterion, the effect of aquifer hydraulic pressure, bedrock thickness, key stratum horizon, key stratum strength and support working resistance on stability of overburden structure were analyzed; (2) to discover the dynamic evolution law of mechanics correlation between key stratum and overburden stratum during coal mining under unconsolidated confined aquifer, to acquire the loads of topsoil layer and overburden stratum transfer into the key strata, and it’s breakage forms at different stage; (3) to establish the mechanical models of compound breakage between key stratum and overburden stratum with considering coupling effect of coal mining and unconsolidated confined aquifer. The research results can provide theoretical basis for risk evaluation of powered support jammed and optimize design of prevention parameters.

松散承压含水层下薄基岩煤层开采，由于其特殊的覆岩结构和水文地质条件，上覆基岩中不能形成稳定的承压拱结构，易发生整体切落，从而导致压架突水事故。采用普氏拱理论、莫尔-库仑破坏准则、“砌体梁”理论与关键层理论相结合的研究方法，借助于理论分析、相似材料模拟、数值模拟与现场实测相结合的综合手段，拟开展如下研究工作：（1）基于局部化带贯通判据，进行覆岩结构极限平衡状态分析，提出松散承压含水层下开采覆岩结构失稳判据，分析含水层水压、基岩厚度、关键层层位、关键层强度及支架工作阻力等因素对覆岩结构稳定性的影响；（2）揭示松散承压含水层下开采顶板岩层之间力学关联及其动态演化规律，获得松散承压含水层下开采不同阶段关键层上覆载荷，及其破断形式；（3）建立工作面开采和松散承压含水层耦合作用下上覆基岩-关键层复合破断力学模型。研究成果为松散承压含水层下开采压架危险性评价及防治参数优化设计提供可靠的理论依据。

针对薄基岩工作面易发生顶板整体切落压架事故问题，采用理论分析、相似材料模拟、数值模拟与现场实测相结合的综合手段对松散承压含水层下采煤覆岩结构失稳致灾机理进行研究。建立采场覆岩“宏观-大-小”结构力学模型，确定不同覆岩结构失稳支架临界工作阻力，分析了关键层上覆载荷对关键层破断形式和破断块体稳定性的影响，并通过UEDC数值模拟软件对典型工程地质条件下采场覆岩结构及应力场演化特征进行了模拟验证。研究结果表明：一般工作面采场覆岩中会自下而上依次形成“支架-围岩”小结构、“砌体梁”大结构、“压力拱”宏观结构。在宏观结构的保护作用下，关键层上覆载荷较小，关键层破断岩块容易形成“砌体梁”平衡结构。薄基岩工作面采场覆岩中无法形成宏观结构，上覆岩层在承压含水层水压力及自重作用下沿煤壁发生全厚整体切落，易造成工作面压架事故。对于单一关键层结构，当工作面临近松散承压含水层时，关键层距离含水层越近，水压越大，则作用在关键层上的载荷越大，关键层“砌体梁”结构越容易发生滑落失稳。研究成果为松散承压含水层下开采压架危险性评价及防治参数优化设计提供可靠的理论依据。