突水溃砂作为一种新型的矿井地质灾害，具有隐蔽、突发、难监测、破坏强等特点，因此，探究覆岩采动劣化特征及突水溃砂致灾机理对松散层水害防控具有指导意义。首先，通过相似材料配比与测试试验，研究了不同材料配比对材料强度、渗透特性的影响机制，并研制出一种适宜于模拟松软岩层的新型固流耦合相似材料；然后，借助采动煤层顶板涌水溃砂灾害模拟系统，进行了浅埋薄基岩、中厚基岩的单一含水结构盖层以及薄基岩含隔双层结构盖层条件下开采的相似模拟试验，分析了不同地层结构的采动裂缝空间劣化−贯通及水砂起动、运移、涌溃灾变特征，揭示了浅埋薄基岩采动突水溃砂致灾机理。试验结果表明：新型固流耦合相似材料兼具耐水、抗崩解、抗软化、低渗透、低强度、低塑性的特性，且渗透系数随碳酸钙含量的增加呈负指数衰减，单轴抗压强度呈现二次多项式增长的特点；初次来压和第一次周期来压阶段是浅埋薄基岩采动覆岩劣化诱发突水溃砂的高发期，采动裂缝平面呈“OX”分布，随基岩与松散层底部黏土层的厚度增加，覆岩由拉剪破坏逐渐转变为拉张破坏，裂缝形态由“垂向直通形”转变为“倒楔形多层交错叠加组合”，裂缝开度减小，通畅度变差，可降低诱发突水溃砂风险几率与危害程度；通道开度（宽度）与砂体粒径的相对关系（简称“裂粒比”）以及通道通畅度是决定突水溃砂发生与否及致灾程度的关键。

As a new type of mine geological disaster, water-sand inrush has the characteristics of concealment, sudden onset, difficulty in monitoring, and strong destruction. Therefore, exploring the characteristics of overlying rock mining degradation and the disaster mechanism of water-sand inrush has guiding significance for the prevention and control of loose layer water hazard. Firstly, the influence mechanism of different material proportioning on the strength and permeability characteristics of similar materials is studied through similar material proportioning and testing experiments, and a new solid-fluid coupling similar material suitable for simulating soft rock layers is developed. Then, by using the test system for water-sand inrush, similar simulation tests are conducted for mining under the condition of a single water-bearing structure capping thin and medium thick bedrock, and a double layered structure capping thin bedrock. The characteristics of mining crack and the disaster mechanism of water-sand inrush under the above strata structure conditions are analyzed. The test results show that the new solid-fluid coupling similar material has the characteristics of water resistance, anti disintegration, anti softening, low permeability, low strength, and low plasticity, and the permeability coefficient decreases exponentially with the increase of calcium carbonate content, while the uniaxial compressive strength exhibits a quadratic polynomial growth characteristic. The first weighting stage and the first periodic weighting stage of mining shallow and thin bedrock are easy to induce water-sand inrush. The mining cracks present an “OX” distribution on the plane, and as the thickness of bedrock and the clay layer at the bottom of the loose layer increases, the bedrock gradually transforms from tensile shear failure to tensile failure, and the morphology of the cracks also changes. At the same time, the opening and smoothness of cracks are reduced, which can reduce the inducing risk and harm degree of water-sand inrush. The ratio of crack opening to sand particle size , as well as the smoothness of crack, are the key factors determining the occurrence and severity of water-sand inrush.