Abstract
The influence of mining on the upper section of working face leads to the fracture of the lateral key block of the roof. From the goaf to the coal body, a group of “left-middle-right” key blocks are formed. According to the three different spatial position structure relations formed by roadway and broken key block in practical engineering, the mechanical causes of broken structure of key block in roof of roadway along goaf are analyzed. FLAC3D is used to simulate and analyze the deformation characteristics and stress state of key block structure model before and after roadway excavation, and the mechanical characteristics and instability mechanism of key block sliding and breaking under three spatial structure modes are obtained. With the help of the mathematical model of material mechanics, the structural mechanical behavior of key block model of roof before and after roadway excavation and the temporal and spatial evolution law of unloading and breaking are studied. The results show that the complex influence factors of mining disturbance and low strength of the weak rock mass will weaken the internal balance of “masonry beam” structure. When the roadway is located below the fracture line of the key block, the middle key block will rotate and lose stability with the side hinge joint of the goaf as the axis; when the roadway is located in the fracture line of the key block, it is easy for the middle key block to slide and lose stability; when the roadway is located outside the fracture line of the key block, the middle key block is in the state of complete collapse, the mechanical transmission mechanism of the surrounding rock in the vertical direction is weakened, and the surrounding rock is the most stable.
Highlights
China’s energy system is characterized by rich coal, poor oil, and less gas, which determines that coal is still the main energy carrier that supports China’s industrial development and economic construction for a long time
Due to the particularity and complexity of deep underground engineering environment, it is still difficult to meet the needs of deep mining to study the deformation and failure mechanism and mechanical evolutionary mechanism of deep rock mass [3,4,5]. erefore, it is a direct way and effective measure to solve the problem by vigorously studying the mechanical behavior and dynamic response law of deep rock mass disaster and promoting the new mining system and mining technology
For the third kind of structural mechanics model, the supporting force at the hinge point of the middle key block is mainly provided by the side coal pillar of the goaf, the load of the left key block is mainly borne by the coal mass that has not been mined, the influence of l area on the left key block and the right key block is small, the surrounding rock pressure and displacement of roadway are the minimum, and the structure is most stable
Summary
China’s energy system is characterized by rich coal, poor oil, and less gas, which determines that coal is still the main energy carrier that supports China’s industrial development and economic construction for a long time. E structural model of roof fracture of secondary gob-side roadway retaining was established by Kan, and the mechanical evolutionary law and stability control technology of overlying rock deformation and failure of secondary gob-side roadway retaining were revealed [10]. E above research provides a generalized model of the broken structure of the key block for the roadway along the goaf, and the mechanical mechanism between the roof of the “masonry beam” structure and the coal mass in the goaf below, the instability process, and the determination method of the key block are given. Rough three-dimensional numerical simulation and theoretical analysis, the mechanical mechanism and deformation law of roof key blocks are revealed under three kinds of spatial structure states, and the judgment basis for the optimal selection of space-time position of gob-side roadway and upper broken key block and disaster prevention and control is provided.
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