Development Characteristics Of Water Flowing Fractured Zone In Weakly Cemented Roof Based On Network Parallel Electrical Monitoring

The Dananhu mining area in Hami coalfield is rich in coal resources,and there are a large number of ten million ton mines under construction or under construction.The roof and floor of coal seam in Dananhu mining area are typical weak cemented strata,and the stability of surrounding rock is not high.Due to the late start of resource development in this area,the degree of geological exploration in the area is still insufficient,and the related basic research work is relatively weak.If affected by mining,the development height and law of water flowing fractured zone are not clear,and other hydrogeological problems endanger the mine production,so it is urgent to carry out relevant research.Therefore,based on the hydrogeological conditions of1801 working face in Dananhu mining area,the field measurement was carried out through the network parallel electrical method dynamic monitoring system,and the numerical simulation was carried out by using FLAC3 D software.The temporal and spatial evolution law of resistivity and stress in the mining process of working face was analyzed,and the development height and law of water flowing fracture zone in working face were obtained.The main research results are as follows:(1)Based on the analysis of hydrogeological conditions of the working face,it is determined that the ?-1 aquifer is directly filled with water in the working face,and the ?-1 aquifer has the characteristics of layered section.The 16 coal water separation section divides the aquifer into two sections,and the hydraulic connection between the two aquifers is not strong.The key point of the study is to determine whether the water guide fracture zone can break through the 16 coal aquifers and conduct the water bearing layer section and conduct the water bearing layer The upper part of ?-1 aquifer has stronger water abundance.Through physical and mechanical tests,scanning electron microscopy and other methods,the typical weak cementation characteristics of overburden rock with low mechanical strength,poor cementation degree,well-developed pores and loose structure were obtained.(2)Based on the principle of network parallel electrical method,the paper constructs a network parallel electrical method dynamic monitoring system to monitor the mining process of working face,and obtains:(1)According to the change characteristics of apparent resistivity in the monitoring area,the maximum height of water guide fracture zone in 1801 working face is 47.59 m according to 3m thickness,and the fracture recovery ratio is 15.86;The development of collapse zone is not obvious,but through apparent resistance The dynamic monitoring of the rate captures the outline of the collapse zone,the maximum height of the collapse zone is 9.6m,the ratio of caving to production is 3.2;the mining fracture angle of the roof in the working face is 69°;(2)According to the change characteristics of the natural potential of the monitoring electrode,the periodic change law of the spontaneous potential in the development of the water guide fracture zone is summarized,and the periodic change law of the self potential is stable and slightly increased in the early stage,the failure fluctuation and the later stage stability The spatial and temporal variation of the natural potential of the monitoring electrode in different depth range can provide a supplementary evidence for the determination of the development height of the collapse zone and the water guide fracture zone.(3)According to the current variation characteristics of monitoring electrode,the characteristics of water flowing fractured zone and caving zone from top to bottom in 1801 working face are summarized.The lower the height is,the more severe the damage degree of rock mass is;the roof collapses once every 4?6m in working face,which is located behind the working face.(3)Based on the distribution of lithology and the change of physical and mechanical parameters,the rock strata of the roof and floor of 1801 working face are generalized.The excavation model is established.30 excavation with a step distance of 10 m is carried out.The results are as follows:(1)When the working face is recovered to 50 m,the roof in the goaf begins to appear tensile stress under the influence of mining,forming a similar "arch" tensile stress area,and the tensile stress value is similar to the working stress The working face mining increases.When the working face is recovered to 250 m,the tensile stress value in the goaf tends to be stable;the stress concentration area appears on both sides of the coal wall of the working face,and the peak value of the pressure stress increases with the advance of the working face;the shear stress of the roof of the working face increases with the advance of the working face,and the shear stress at both ends of the working face expands upward and the range increases,showing the "head" at both ends of the working face The distribution of "big tail and small".(2)Under the action of mining,the strata on the roof of the working face subside,and the vertical displacement nephogram shows obvious "arch".With the progress of working face mining,the collapsed strata are refilled under the action of re compaction force,the range of mining influence is expanded,and the deformation has gradually expanded upward.When the working face stops mining,the subsidence of the goaf rock mass on the working face roof increases from top to bottom,and the maximum value appears in the middle of the goaf.(4)Based on the research results of field measurement and numerical simulation,a comprehensive comparative analysis is carried out,the results are obtained:(1)Through the comparison and analysis of the development height of the water guide fracture zone by empirical formula method,analogy method,network parallel electric method and FLAC3 D numerical simulation,it is found that the empirical formula is not suitable for weak cemented roof,and the measured results and simulation results have good correspondence.The development height of the water guide fracture zone determined is 50 m,the fracture recovery ratio is 16.7,which is at the height of 16 coal aquifers The results show that the 16 coal aquifers effectively resist the development of the damaged zone,and the aquifer of the upper part ?-1 is not damaged by mining.(2)Through the analysis of the corresponding relationship between the vertical stress,shear stress,horizontal stress of numerical simulation monitoring points and the resistivity data obtained from field measurement inversion,it is obtained that the change of shear stress in the mining process of working face has a good correspondence with the change of resistivity,which reflects that the change of shear stress is ahead,and the change of resistivity has a certain lag.In the same depth range,the change of resistivity affected by mining is more severe than that of shear stress.The development process of water flowing fractured zone can be analyzed by the change of resistivity in different depths.There are 44 figures,10 tables and 80 references in this paper.