The Study Of The Stress Distribution And Failure Law In Repeated Mining Of The Old Mining Damage Zone

In the 1980 and 1990 s of the last century,because of the lack of technical and equipment conditions,local small coal mines have long-term used reamer-pillar,pillar(high-fall)and other old coal mining methods,and their recovery rates were less than 30%.consequently,this situation brings about a large number of high-quality coal resources left in the goaf area,which cause a great waste.It is of great practical significance to realize the sustainable development of the mine by realizing the re-exploitation and utilization of the old mining and residual coal and making full use of the precious coal resources.Based on the test of coal rock creep,the orthogonal experiment design method is used to study the effect of various mining factors on the coal pillar stability of the old mining area.The stress distribution and failure law of the coal pillars with different stability in the mining face are studied by numerical simulation,and the stress distribution and failure law of the coal and rock under pre-grouting conditions are studied either.This paper provides a theoretical basis for the technology of residual coal re-mining.The main work is as follows:1.In order to study the influence of mining factors on the stability of coal pillars in old mining areas,the creep test of coal rock compare the applicability of Xiyuan model and Xiyuan acceleration model to describe the creep characteristics of coal in Shenghua Coal Mine.Which obtained the suitable description of the creep characteristics of coal and rock in Shenghua Coal Mine and the creep parameters of the constitutive model.2.Compared the results of the numerical simulation and creep test,this paper studies the effects of coal pillar width,roadway width and roadway height on the maximum vertical stress and the maximum shear stress in coal pillars.The results show that the factors that have the greatest influence on the core area of coal pillars are the width of their own pillars and the height of roadway.The most significant factor affecting the maximum vertical stress and maximum shear stress in coal pillars is the width of the alley.The mathematical modelthat reflects the relationship between maximum vertical stress,maximum shear stress and mathematical factors of coal pillar in old coal mining area of Shenghua Coal Mine isestablished.3.This paper researchs the influence of the change law of the stress field and the stability of the coal pillar on the stress field of the mining face.And the results show that when the working face is advanced,the peak value of the stress lies in the coal pillar or the pillar in the front of the working face.When the core area of the coal mining area is 45%,the initial collapse step is 14 m and the basic top fault step is 17 m.When the core area of the coal mining area is 70% The initial break step is 16 m,the basic top of the break step is 18 m.4.The influence of the super-high water material pre-grouting on the change of the stress field in the mining face of the old mining area is analyzed.The results show that the materials have a certain carrying capacity,stress concentration of the advanced support pressure is always located at the front coal in the face of the working face,and the initial collapse step is 20 m.Compared with the non-grouting,the pre-grouting in the roadway has played a positive role in controlling the stability of the surrounding rock and roof in front of the working face.