多场耦合作用下覆岩破断失稳致灾机理及控制研究

There’s abundant coal reserves in shallow thin bedrock in west China. High-intensity mining is easy to cause roof disasters like water-sand bursting and compressive failure of supports, thus causing huge losses. When the mining-induced fractures are covered by unconsolidated water-bearing strata, the water-sand fluids will seepage along fractures and influence the fracture law of overlying strata. It belongs to a typical multi-field coupling mechanics problem under the collaborative effect of water, sand and rocks. Based on the independently developed test system of water-sand seepage in cracking rock mass, an experimental research on water-sand seepage of cracking rock mass was carried out by theoretical analysis, laboratory test and numerical calculation. The calculation model of equivalent coefficient of viscosity of water-sand seepage in cracking rock mass was constructed. Influences of water-sand seepage on fracture characteristics of the main roof structure under different stress conditions were explored through a simulation test of similar materials. The mechanical model of main roof structure under the water-sand seepage effect was established to study the stress field distribution pattern in mining-induced cracking rock mass under water-sand seepage effect. The main roof structural stability criteria were put forward and the disaster mechanism caused by main roof instability under multi-field coupling was disclosed. A stope support-surrounding rock calculation model under the multi-field coupling was constructed to study the support-surrounding rock interaction. The roof disaster control technological system under multi-field coupling was established, which could provide new theoretical basis for roof disaster control in coal seam of shallow thin bedrock.

我国西部浅埋薄基岩煤层储量丰富，高强度开采时容易引起突水溃沙、压毁支架等顶板灾害，造成重大损失。采动裂隙沟通上覆松散含水层时，水沙两相流体将沿着裂隙发生渗流力学行为，影响覆岩破断规律，属于典型的水-沙-岩体共同作用下的多场耦合力学问题。本项目拟采用理论分析、实验室试验、数值计算等方法，在自行研制裂隙岩体水沙两相渗流试验系统的基础上，开展裂隙岩体水沙渗流试验研究，建立裂隙岩体水沙渗流等效粘滞系数计算模型；通过相似材料模拟试验，研究不同应力条件下水沙两相渗流对基本顶结构破断特征的影响；建立水沙渗流作用下的基本顶结构力学模型，研究水沙渗流作用下采动裂隙岩体应力场分布规律，提出基本顶结构稳定性判据，揭示多场耦合作用下基本顶失稳致灾机理；建立多场耦合作用下采场支架-围岩计算模型，研究支架-围岩相互作用关系，构建多场耦合作用下顶板灾害控制技术体系，为浅埋薄基岩煤层顶板灾害防控提供新的理论依据。

我国西部浅埋薄基岩煤层储量丰富，适宜采用大采高、快速推进的强采动方式开采。然而，高强度开采方式容易导致采场覆岩滑落失稳，诱发顶板压架和突水溃沙等多种并发重大灾害事故。本项目综合采用室内试验、理论分析、数值计算、现场监测等方法，对多场耦合作用下覆岩破断失稳致灾机理及控制进行了研究，设计并开发了一套多功能岩体裂隙渗流试验系统，实现了任意组合交叉裂隙和颗粒运移条件下裂隙渗流规律的测试功能；开展了单一裂隙岩体水沙渗流试验，建立了考虑颗粒碰撞的裂隙含沙渗流渗透系数计算模型，并通过试验结果拟合得到模型参数；建立了多场耦合下基本顶“梁-拱”型破断结构力学模型，提出了厚硬粘土薄基岩条件下基本顶“梁-拱”破断失稳判据，得到了不同厚度基岩和粘土层条件下顶板各岩层的下沉速度变化规律；研发了新型流固耦合相似模拟材料，开展了特厚煤层开采顶板含水层水体下泄致灾的物理似模拟和数值模拟试验，得到了多场耦合下顶板破断特征及突水致灾机制；分析了多场耦合作用下支架-围岩相互作用关系，确定了不同基岩厚度综放开采条件下工作面所需的合理工作阻力，提出了薄基岩厚煤层放顶煤开采时，支架-顶板下沉量之间仍然符合双曲线关系；提出采用水沙两相流改性及选择合理的支架工作阻力等控制措施，构建了多场耦合作用下顶板灾害控制技术体系。本项目的研究成果丰富了覆岩运动的理论体系，并对浅埋薄基岩煤层开采过程中产生的顶板压架、突水溃沙等灾害预防具有重要的理论指导意义。