Study On Supporting Mechanism And Technology Of Roadway Along Next Goaf In Ultra Soft Thick Seam

Coal is a precious non-renewable resource.It is one of the development trends of the coal industry to improve the coal recovery rate as far as possible on the premise of safety,feasibility and economy.According to the scientific conception of precise mining of coal,which is proposed by academician Yuan Liang of the Chinese Academy of Engineering,precise mining of coal is the only way for the future mining of human society.This research on supporting technology of roadway along next goaf in ultra soft thick seam is a case of precise mining.Currently,there are just a few project cases of roadway along next goaf in our country.The public literature shows that since 1949,only 5 cases have been implemented in China,of which 4 cases have corresponding coal seam thickness of 2m,and belong to medium hardness coal seam.This case is the only one classified as extremely loose and low strength coal seam of 8m thickness.Therefore,the research of this project is still a new thing.This technology can not only improve the recovery rate of coal,but also save water exploration steps,improving the dig speed,ensuring the timely replacement of the working face,and avoiding the off production of coal mines.The main research work of this doctoral dissertation is as follows:(1)According to the collected data,the complex engineering geology and hydrogeological conditions of the 8100 roadway are acquired,and the factors of water,harmful gas and residual coal spontaneous combustion are analyzed,providing theoretical support for the implementation of roadway along next goaf.(2)Mechanical properties of the rock,such as tensile strength,compressive strength,deformation modulus,elastic modulus,and Poisson's ratio,are tested in laboratory.And horizontal pressure coefficient,uniaxial compression strength,and triaxial compression strength with seven levels confining pressure of briquette coal are tested.Then,based on the Mohr-Coulomb criterion and test results above,cohesive strength and internal friction angle of the loose coal are calculated,and hardness of the rock can be classified.(3)Based on the mechanical model of the surrounding rock deformation partition of the axisymmetric circular roadway,and the creep characteristics of the coal and rock,the mechanical model of caving arch is established and the deformation partition of the entitative coal side is analyzed.The distribution regularity of radial stress in entitative coal side,and the solution method and calculation formula of each partition are given,which lay the foundation for the determination of the unsymmetrical support parameters in the roadway along next goaf.(4)Through the ABAQUS finite element software,the displacement and stress distribution around the roadway is calculated and analyzed.Meanwhile,by comparison between the parse results and simulation results,the two mutual evidence are used as the basis of support design.(5)According to the characteristics of solid coal side in roadway,the corresponding mechanism and principle are proposed through the effect of loose and crushing coal.The supporting effect of bolt,and the "coal + scaffolding + bolt"integrated system in supporting mechanism analysis is provided.(6)A mechanical model is established for three supporting forns of U steel support,two row bolting reinforced U steel support,three row bolting reinforced U steel support.The bearing capacity is calculated by Matlab mathematical calculation software.The stress condition inside and outside of U steel scaffolding is analyzed.The supporting effect under different conditions is compared and analyzed,and the weak part is obtained,and the reasonable location of reinforcing anchor is determined.(7)Consolidation effect between bolt and loose coal seam is proved to be existence according to the test result of drawing force of bolt in field loose coal seam.The measurement and analysis of the interaction force between surrounding rock and metal support,the pulling force of anchor bar and the change of supporting pressure of working face are carried out accurately.All the basic research work provides first-hand information for the support design of the roadway along next goaf.(8)The reasonable support scheme for the roadway is proposed,and the support technology is applied on site.The distortion of roadway around reinforcement is contrasted and analyzed,and the scientificity and rationality of supporting mechanism and supporting scheme are verified through acquired monitoring results on site.This doctoral not only comprehensively analyzes the restrictive factors of fully gob side entry driving in deep and very loose coal seam,but also provides an effective way for the realization of precision coal mining.The results of the study not only have high theoretical value academically,but also have a very important practical significance in engineering.