Study On The Influence Of Roof Drainage On Weighting Step In Hulusu Coal Mine

With the continuous mining of Water-rich mines with complicated hydrogeological conditions,the roof accidents of Water-rich mines are frequent,and the research on the rule of the roof breaking distance before and after drainage in water-rich working face is particularly important,this paper focuses on the change of weighting step before and after roof drainage,taking 21103 working face of Hulusu coal mine as the research object,and characterizing roof drainage with the change of physical and mechanical properties of overburden before and after roof drainage,by means of theoretical analysis,physical similarity model test and numerical simulation,the variation law of weighting step before and after roof drainage in fully mechanized coal face is studied.(1)Based on the key layer theory,the key layer which influences the weighting step is determined,and the key layer is simplified into fixed beam model and cantilever beam model respectively according to the primary and periodic breaking force forms of the key layer,it is analyzed by the theory of elasticity.Through theoretical analysis,the first weighting step and periodic weighting step are obtained before and after roof drainage.(2)Based on the test results of physical and mechanical properties of multiple overburden rocks under two water-bearing conditions and the field geological data,two groups of physical similarity model tests are constructed,and the proportioning schemes of two groups of test similar materials are determined,monitoring scheme of stress and displacement.Through two groups of similar model tests,the weighting step of the working face before and after the roof drainage is obtained.At the same time,through the analysis of the similar model test results,we can get the caving displacement characteristics of the overlying strata under the influence of the key strata failure,the change law of the overlying strata stress and the evolution law of the mining stress during the working face mining.(3)Using FLAC3 D software to establish two sets of numerical simulation models to simulate the change law of surrounding rock stress in the process of working face before and after the roof drainage.Based on the theoretical analysis,it can be concluded that the failure of the key stratum is mainly tensile failure,and monitoring points are set in the key stratum before the model excavation,the first breaking distance of key stratum before and after roof drainage can be obtained.(4)Comprehensive theoretical analysis,similar model test and numerical simulation results are used to analyze and summarize the variation law of weighting step and surrounding rock stress before and after the roof drainage,it provides theoretical guidance for roof management of working face and reference for other similar mines in China to solve such problems.