Research And Application On Width Of Protection Coal Pillar Under Condition Of Compound Rock Strata

In order to increase the recovery of coal resources in the process of coal mining, working faces have to be arranged under highway when surface of mining exist developed highway system. It is very important that study on reasonable dimension of protected coal pillar under highway, which ensure safe and efficient production, and then ensure highway’s normal operation.During mining course, causing roof caving and overlying strata’s movement, which even spread to surface of earth and bring about architecture destruction. Generally, reasonable dimension of protected coal pillar can effectually reduce deflection of earth surface, of course affected area of earth surface’s sink have relationship to displacement angle of rock stratum. Based on researching which displacement angle of rock stratum influence on earth surface’s sink, the paper set1312working face of Sanyuan coal as background to study on arrange reasonable dimension of protected coal pillar, the main research conclusions as follows:(1)Based on analyzing mining geology, combined theories of critical layer and thin plate, the paper got conclusions that the sinking model is elliptic basin and critical layer is main control action to overlying rock movement. Through forming stress balanced arch structure in critical layer, the overlying rock can transfer upper loads to two-sides coal pillars and control the movement of rock stratum. (2)Working out that displacement angle amounts of rock stratum decide overlying rock moving range and sinking level by analysis, the main influence factors of rock stratum’s displacement angle include surrounding rock properties, buried depth of coal seam, thickness of mining, coal seam’s angle of inclination, processing method of worked out section and overlying strata fault.(3)We got deformation laws of coal seam by earth surface’s observation of working faces which are adjacent to1310working face of Sanyuan coal:The maximum of coal seam’s inclination was3696mm, gradient was34.4mm/m curvature was0.4～-0.9×10-3/m, horizontal movement was1087mm, horizontal deformation was10.4-29.5mm/m. The maximum of coal seam’s strike was4298mm, gradient was29.6mm/m, curvature was0.3～-0.4×10-3/m, horizontal movement was956mm. horizontal deformation was5.7～-8.2mm/m. So the mining condition of this working face is not enough mining, the strike’s sinking value was bigger, the maximum point of sinking located middle position in worked out section, inflection point located upper boundary of worked out section, edge of sinking basin was stress tension zone, and middle part was compression zone. Through reverse calculation of observation data, we got that movement angle of earth surface ψ=55°, strike movement angle δ=55°,dip movement angle β=65°, rise movement angle γ=66°(4)According to protection class of highway was I grade, we determined width of protection belt was20m, and adopted modified vertical method to got the width of two-sides protection coal pillar was at least246.5m in1312working face after determined overlying stratum movement angle parameters Using FLAC3D simulation, the paper gat overlying stratum movement laws in different loose bed thickness and different width of working faces by combining actual geology of1312working face in Sanyuan coal. Along with increase of scattered mining and width of working face, the maximum sinking value and sinking coefficient and influence zone would be increscent tendency. Then when earth surface thickness was180m and width of working face was200m,because the influence zone would reach to245m, the protected coal pillar should be arranged out of influence zone. Finally, by theoretical calculation and numerical simulation got out contrast size of protected coal pillar, we picked up maximum amount between two methods as protected coal pillar’s size that is246.5m in the condition of ensuring highway safety.The research results can provide reference value to similar engineering geology of mining.