Study On The Top Pressure Relief Mechanism And Parameters Of Thick And Hard Roof

The geological conditions of thick and hard roofs are widely distributed in our country.This type of roof generally has the characteristics of high strength,large thickness and strong integrity.During the mining process,the characteristics of large suspended roof area and long caving step distance often appear.As a result,the mine pressure of the stope appears strong,the surrounding rock of the roadway around the stope is destroyed and deformed,and the support body deteriorates and fails.For this reason,this article aims at the problem of serious damage and deformation of the roadway under the condition of thick and hard roof,which is affected by the mining of adjacent working faces,and comprehensively uses a variety of research methods to systematically analyze the mining of roadways in adjacent working faces under the condition of thick and hard roof.The reason for the strong dynamic impact,and the comparative study of the overlying rock migration law and stress evolution characteristics before and after blasting roof cut and pressure relief,reveals the mechanism of blasting roof cut pressure relief on improving the stability of adjacent roadways,and explores under this premise The influence of different roof-cutting and pressure-relief engineering parameters on the effect of roof-cutting and pressure-relief is discussed.Finally,based on the optimized engineering parameters,a roof-cutting and pressure-relief scheme suitable for actual mines is designed.The main research results include the following five aspects:(1)Based on the drilling and blasting methods,the rock mass partition damage under drilling conditions is studied and the method for determining the range of each damage partition is explained.The LS-DYNA numerical analysis method is used to verify the partition damage,and the drilling and blasting conditions are obtained.The radius of each damage zone and the development and expansion of burst cracks.(2)Aiming at the phenomenon that the long overhang distance of the thick and hard roof leads to the excessive load of the overlying rock in the bearing goaf,the collapse characteristics of the thick and hard roof during the mining process of the working face are first analyzed,and then the cantilever beam model of the thick and hard roof is established and calculated The load-bearing load and limit caving distance of the thick and hard roof.Finally,the load estimation method is used to calculate the difference in the load-bearing state of the coal pillars before and after the roof is cut and relieved.Mechanism of action.(3)In the similar simulation experiment,a comparison scheme of non-cut top pressure relief and cut top pressure relief was set up,and the overlying rock migration law and stress evolution characteristics of the respective schemes during mining were analyzed,and the thick and hard roof after cut top pressure relief was analyzed.It will break along the weakened position of the blasting damage,and the overlying rock will break simultaneously and break and sink with the thick and hard roof.At this time,the overlying rock load originally applied to the coal pillar and the adjacent working face roadway area falls into the mined area,Which greatly reduces the impact of mining on the roadway,and verifies the beneficial effect of the cutting roof pressure relief method on improving the stability of the adjacent working face roadway.(4)Based on the engineering conditions of coal seam mining under the thick and hard roof,the 3DEC numerical analysis method is adopted to set up different roof cutting angles and roof cutting height schemes.The overlying strata migration law and stress evolution characteristics under each scheme are calculated and analyzed.The influence of different roof cutting and pressure relief engineering parameters on the pressure relief effect.(5)Based on the actual engineering and geological conditions of 15201 and 15202 working faces of a mine in Jincheng,Shanxi,the parameters of the top-cutting and pressure-relief engineering were determined,and a blasting and top-cutting and pressure-relief plan suitable for the mine was designed for the subsequent implementation of the blasting and pressure-relief project provide technical support.There are 47 figures,9 tables and 86 references in this thesis.