Overlying Rock Movement Of Shallow Coal Seam In Gully Terrain Study On The Development Law Of The Water Conducting Fracture Zone

In this paper,theoretical analysis,numerical simulation and field measurement are used to systematically study the mechanism of overburden breaking,the law of mine pressure appearance and the law of fracture development when mining in the shallow coal seam in valley and gully terrain and under similar geological conditions,especially for the whole roof cutting during the mining process of 3301 and 3302 working faces in zhujiamao coal mine of Yushen mining area The main research results are as follows:(1)The formation mechanism of overburden fracture "cut body" structure under the condition of gully topography is analyzed theoretically.The additional stress(load)model on the uniform load of ravine terrain is established by using the theory of horizon discrimination,elastic mechanics and material mechanics.The additional stress(load)brought by the flat top of Valley peak and the slope of Valley peak is calculated respectively.The models of fixed beam and cantilever beam are established,and the formulas of the initial and periodic weighting steps of the basic roof of 3302 working face(under the condition of uniform load)are derived.This paper summarizes the height of the water diversion fracture zone under the similar geological conditions in Shendong mining area,and sorts out the theoretical calculation formula of the height of the water diversion fracture zone under the geological conditions.It provides a certain theoretical basis and reference for the mines under similar geological conditions in the future.(2)The model of zhujiamao 3302 working face is built by UDEC software.The numerical simulation calculation of the roof weighting step distance and the overlying rock movement law affected by mining is carried out.The rules of the shallow coal seam pressure appearance and overlying rock fracture evolution under the condition of ravine terrain are vividly reproduced.The initial weighting step distance,periodic weighting step distance and water diversion crack of the face are obtained by simulation calculation It is found that the thickness of the surface soil layer(load size)has an obvious effect on the step distance of the working face.The fracture evolution law generally shows that the closer to the working face and the shorter the time is,the more obvious the fracture development is:the farther away from the working face and the longer the time is,the less developed the fracture is,and it has been basically compacted to the middle of the goaf,which indicates the time-space relationship between "mining influence and overlying rock fracture development".(3)Through the processing and analysis of the real-time monitoring data of the support pressure in the working face of zhujiamao 3302,the first pressure step of the direct roof,the first pressure step of the basic roof and the periodic pressure step are obtained.The correctness of the theoretical analysis and the numerical simulation results are verified.Through the analysis of the support data in the working face,the adaptability of the support to the mining under the geological conditions is verified.This paper sums up the tendency of ore pressure appearance under this geological condition.Based on the field measurement,the actual height of the water diversion fracture zone in zhujiamao 3301 working face is 50%higher than the calculation result of the recommended formula in the third mining specification,but the similarity between the results of the fitting formula derived in Chapter 3 is about 5%.The correctness of the theoretical calculation and numerical simulation results is verified again,and the corresponding management measures are proposed for the working face under the geological conditions.