Research On Reasonable Coal Pillar Width And Support Technology For Dynamic Fully-mechanized Caving Roadway Along Gob

When driving gob-side entry under unstable overburden,the surrounding rock of some sections of roadway is not only affected by the excavating and the mining of the face,but also will be subject to dynamic pressure caused by the lateral movement of the basic roof near the working face,and the difficulty of surrounding rock control has been greatly improved.Based on the engineering background of the gob-side transportation entry of 9102 fully mechanized top-coal caving face in Hengsheng colliery,this paper uses the methods of on-site investigation,theoretical analysis,numerical simulation and engineering practice to systematically study the reasonable coal pillar width and support technology of the gob-side entry subject to dynamic pressure.Firstly,the fracture and deformation characteristics of surrounding rock of 9102 entry were observed by borehole peeper and multi-point displacement meter through field investigation,and the causes of deformation and failure of roadway and the problems existing in original support were preliminarily analyzed.Then,the overburden structure model of gob-side roadway was established to calculate the size of key blocks,fracture location and pillar width.Flac3 D numerical simulation software was used to study the stress distribution and displacement evolution characteristics of surrounding rock of roadway during roadway excavation and mining with different width coal pillars,which provided a reference for determining reasonable coal pillar width.Then the numerical models were constructed to study the coupling effect of bolts and cables combined support.The sensitivity of surrounding rock to four supporting parameters,i.e.pre-tightening force of bolts and cables,length and spacing of cables,was judged by visual analysis method,which provided a basis for roadway support design.Finally,the width of the coal pillars of the roadway was determined and the surrounding rock control measures were proposed.The simulation and field tests were used to verify the rationality of the support scheme and coal pillar retention.The main conclusions of the paper are as follows:1)The main reason of surrounding rock deformation of gob-side entry in 9102 fully mechanized top-coal caving is the shortage of mining and development replacement.During the excavation process,the roadway is affected by the lateral thick and hard basic roof break and the rotary subsidence of the adjacent 9104 fully mechanized caving face.Therefore,the surrounding rock appeared severely broken and the internal separation crack developed.2)The length of the key block B of the lateral basic roof in the advancing direction of 9104 fully mechanized top coal caving face and the breaking length of the lateral coal mass are 10.5m;the breaking position is 4.54 m away from the edge of the goaf,and the reasonable width of the coal pillar is 10 m.3)The compressive stress zone coupling coefficient was defined to evaluate the support performance of each test.The relationship between the effective support height and the coupling coefficient of compressive stress zone is obtained by regression analysis.When supporting the surrounding rock of 9102 entry,the coupling coefficient of compressive stress zone should be greater than 1.4.The spacing of cables in surrounding rock of gob-side roadway in 9102 fully mechanized top-coal caving has the most significant effect on the height of effective support stress field.The influence of force and length of cables is in the middle of four factors,and the influence of force of bolts is the smallest.4)The industrial test shows that the width of coal pillar is reasonable and the support scheme meets the requirements of controlling the deformation of surrounding rock.Figure 53 table 4 reference 87...