Study On Activated Stress Evolution Of Mining Faults And Coal Pillar Setting-up

Fault activation is one of the major hazards endangering mine safety.Strengthening the study of fault activation law and determining the size of coal pillar for coal mine fault safety are of great significance for fault activation water inrush and reducing human and economic losses.This paper summarizes the types and activation conditions of fault water inrush at home and abroad,as well as the variation law of stress in fault activation body and fault safety coal pillar.On this basis,this paper studies the mining activation of faults by analyzing the dynamic analysis of stress variation at faults and combining with indoor model test and numerical simulation.On the basis of Hongdunzi mining area in Ningxia,Hongsi Coal Mine,this paper studies the geological structure and hydrogeology of this area,and finds that the fault cuts off the whole Shanxi Formation stratum and extends to the aquifer at the lower end of Paleogene stratum.With the increase of mining size of coal mine,the fault will produce new damage,which makes the water of the upper Paleogene sandstone aquifer enter the roadway along the fault.It caused water inrush.Through reading a large number of literature,this paper makes a reasonable analysis of the activation process of faults.The analysis shows that faults have a certain barrier ability relative to normal strata,and this barrier ability can change the stress in the fault body.The main reason for the activation of faults is that the barrier ability in the fault body is accumulating continuously due to coal mining,which makes the fault position appear.The force is concentrated,so that the fault slips and cracks occur.A model test was conducted to study the evolution law of fault activation stress in the study area.The dynamic evolution of normal stress and tangential stress of fault and the change trend of "two zones" of roof under coal mining were analyzed.The results show that only when the normal stress at the fault decreases and the tangential stress increases during the mining of coal mines with faults can the faults be activated and water inrush occurs.And with the increase of the size of the coal mine,the development height of the "two zones" of the roof increases relative to the normal stratum.In this paper,two numerical simulation schemes are designed,one is horizontal stratum,the fault dip angle is 55 degrees,the other is 6 degrees and the fault dip angle is 55 degrees.The stress variation trend of fault zone under mining influence is analyzed.Combining with the change of plastic zone,the size of safe coal pillars in two environments is obtained.Under the first condition,the size of safe coal pillarsshould be 30 meters.Under the second condition of coal seam mining,the size of safe pillar should be 35 meters.