| Aiming at the problem of surrounding rock stability control of gob side entry retaining in thin coal seam,this paper takes the gob side entry retaining in 5449 working face of beipingdong coal mine of Baoyuan mining company as the background,and uses the methods of theoretical analysis,similar simulation test,numerical simulation and field test to deeply explore the variation law of surrounding rock stability of gob side entry retaining,and obtains the best roof cutting angle and height of beipingdong coal mine,This paper reveals the coupling mechanism between the rock mass fracture propagation and the stress of the supporting structure in the gob side entry mining,and obtains the key bolts that inhibit the overall instability of the roadway,providing experimental guidance for further optimizing the roadway bolt support layout.After simulating and optimizing the supporting structure,the field industrial test scheme is proposed in combination with the actual situation on the site.The main results of this paper are as follows:(1)The longer the lateral cantilever length of the basic roof of the gob retaining roadway,the greater the support resistance provided by the roadway side wall support.After roof cutting and pressure relief,the basic roof of the working face will be sheared along the pre split face,so that the roof of the goaf can collapse along the pre split face in advance,thus reducing the length of the lateral cantilever,thus reducing the stress load on the filling body near the roadway.The severe pressure increase caused by roof collapse is effectively avoided.At the same time,the roof collapse within the roof cutting range can fill the goaf and give support to the overlying strata to a certain extent,so as to alleviate the stress concentration in the reserved roadway area.(2)Adopting the method of directional blasting to cut the roof can reduce the high demand for roadway side support resistance.Through theoretical analysis,the reasonable range of cutting height and cutting angle is obtained.The influence of key blocks on cutting angle and cutting height is discussed.The optimal cutting angle is 12 ° and the optimal cutting height is6.5m.(3)Through similar simulation,the dynamic evolution characteristics of overburden collapse during the mining process of the coal seam with gob side entry are analyzed.At the initial stage of mining to 6m and 7m of the working face,the strata above the side of the gob are separated under the influence of mining,and the separation range extends to 16 M above the gob.Longitudinal cracks appear at the upper right of the roadway and run through the whole main roof,and the low-level strata fracture develops to the high-level strata,The filling body beside the roadway extrudes to the side of the roadway with a small part falling off;At the later stage of 8m and 9m of the working face,all the low rock strata at the side of the Goaf Collapse and fill the goaf,the cracks at the upper right of the roadway extend to the upper part of the roadway,and the entire overlying strata fracture along the cracks and subside to the side of the goaf,and the filling body near the roadway is crushed and lost its supporting capacity.(4)At the initial stage of mining in the working face,the main deformation is bending deformation.The subsidence of the coal roof is greater than that of the roadway roof,and the maximum displacement reaches 182.1mm at 2m above the working face;At the later stage of mining,the self weight of the overlying strata shifts to the side of the goaf as a whole,and most of the filling bodies near the roadway are crushed.The support effect is reduced,and the subsidence speed of the collapsed rock is gradually slowed down by compaction.The maximum subsidence is 5m above the right side of the roadway,and the maximum subsidence reaches359.6mm respectively.(5)By analyzing the monitoring data of bolt axial force,this paper reveals the role of bolt in restraining roadway deformation during mining,obtains the key bolt in roadway support,and further optimizes the layout of roadway bolt support.The results show that the roof bolts play a key role in restraining the deformation of the roadway,especially the bolts near both sides of the roadway bear a large stress,and the side bolts mainly play a role in strengthening the stability of the side.(6)The subsidence at each position of the roadway roof gradually approaches a fixed value with the increase of the roadway side filling body width.When the filling body width is 2.5m and 3M,the filling body has sufficient strength and bearing capacity,and the roof can be effectively controlled and the support effect is the best.When the width of the filling body increases to a certain width,the change of the vertical stress of the surrounding rock of the roadway has little effect,and its sensitivity to the increase of the width of the filling body is low.With the increase of the width,the stress distribution at the part of the filling body will be uneven.Therefore,it can be inferred that the greater the width of the filling body is,the better.By analyzing the distribution of plastic zone under different filling width,it is concluded that increasing the filling width may lead to the increase of plastic zone range in some areas.Therefore,the distribution range of plastic zone and the filling width are concave parabola.Therefore,it is determined that the optimal filling width should be 2.5m.(7)By simulating the surrounding rock displacement of the roadway before and after the optimization scheme,it is concluded that the roof anchor beam is used to strengthen the support along the roadway direction at the side near the coal wall on the west side of the return air roadway,and the surrounding rock displacement is effectively controlled by setting an anchor cable on the anchor beam 5 °-10 ° facing the mountain. |
PDF Full Text Request