煤层一次采出厚度变大，导致直接顶冒落高度增加，并且在薄基岩条件下，顶板破断后不容易形成稳定的结构。顶板破断容易导致工作面突水溃砂灾害的发生,严重影响工作面的生产。为了揭示薄基岩、厚松散岩层在高强度开采条件下突水溃砂和顶板切落并发灾害机理，利用自主研发的顶板动压与突水溃砂试验平台进行了相似模拟试验，以锦界煤矿31406综采工作面为工程背景，试验采用平面应变模型，选取几何相似比为100∶1，结合辅助红外成像仪和超声波探测器等获取了顶板破断时能量的聚集与耗散特征以及裂隙的发育特征。试验结果表明：顶板发生超前破断时，同一岩层产生竖直贯通裂隙，在层理处因岩层强度和厚度不同容易产生“错动”裂隙；突水溃砂和顶板切落并发时产生了明显的动载冲击现象，支架工作阻力会有明显增加，引起压架和工作面发生突水溃砂事故；基于滚动摩擦基本原理建立了滚动摩擦力学模型，揭示了水砂涌入裂隙后导致块体产生滑落失稳的力学机理；水砂体由贯通裂隙进入顶板结构，原有滑动摩擦向滚动摩擦转化，显著降低块体间摩擦力，使顶板产生滑落失稳。结合试验和理论分析得到及时移架，增加支架初撑力，加快工作面推进速度等可以降低突水溃砂和顶板切落灾害发生的概率。

The coal seam thickness in one-time mining becomes larger, which leads to an increase in the height of the direct roof caving, and under the condition of thin bedrock,it is not easy to form a stable structure after the roof breaks.The breakage of the roof can easily lead to the occurrence of water inrush and sand burst disasters in the working face, which seriously affects the production of the working face.In order to reveal the mechanism of concurrent disasters caused by water inrush and sand burst and roof cutting under high-intensity mining conditions in thin bedrock and thick loose rock formations, similar simulation experiments were performed using the self-developed roof dynamic pressure and water and sand burst test platform, taking the No.31406 fully-mechanized mining face of Jinjie Coal Mine as the engineering background, the plane strain model was used in the test, and the geometric similarity ratio was selected as 100∶1.combined with auxiliary infrared imagers and ultrasonic detectors, which obtained the characteristics of energy accumulation and dissipation and the development of cracks when the roof was broken. The test results show that when the roof breaks in advance, vertical through cracks are generated in the same rock layer, and the bedding is prone to“displacement” cracks due to the different strength and thickness of the rock layers. When water bursts and sand breaks and roof cuts occur concurrently, obvious cracks are produced, and the working resistance of the support will increase significantly, causing water burst and sand burst accidents in the pressure frame and working surface; based on the basic principle of rolling friction, the rolling friction mechanics is established. The model reveals the mechanism of the block slipping and instability caused by the influx of water and sand into the fissure; the water-sand body enters the roof structure from the through cracks, and the original sliding friction is transformed into rolling friction, which significantly reduces the friction between the blocks and causes the roof to slipunstably.Combined with experiments and theoretical analysis, it is found that timely support frame removal,increased support setting force, and acceleration of the advancement of the working face can reduce the probability of occurrence of water-sand inrush and roof cutting disaster.

0 引言

1 顶板动压与突水溃砂试验平台

   1.1 试验台主体及特征

   1.2 顶板破坏观测

   1.3 模型设计与模型铺设

2 试验结果与分析

   2.1 顶板破断、失稳与裂隙发育规律

   2.2 突水溃砂和顶板切落并发灾害

   2.3 支承压力、支架工作阻力变化规律

3 顶板切落灾害的力学分析

   3.1 顶板块体间滚动摩阻因素力学机理

   3.2 不同摩擦阻力下顶板稳定性分析

4 结论