Research On Controlling Mechanism Of Surrounding Rock Around Gob-side Entry Retaining In Deep Coal Mine With Large Section

Coal mining growing to deep and adoption of large section roadway is the inevitable trend of development of the coal mine in our country, and the gob-side entry retaining technology is one of the developing directions of modern coal mining. Therefore it has important theoretical value and engineering significance to research on the stable mechanism of surrounding rock and its control technology of gob-side entry retaining with large section in deep mine.The main research work and the main results are as follows:1) By using the methods of field test, physical simulation and numerical simulation, characteristics of strata behavior in deep gob-side entry retaining with large section were investigated, results showed that:the front of the working face can be divided into two stages:the initial stage and the obvious stage; the rear of the working face can be divided into three stages:the speed increase stage, the speed decrease stage and the speed steady stage; the influence ranges, surrounding rock deformations and deformation speeds of large section deep Guqiao Mine1115(1) of each stage are much larger than those of shallow small section of Wolonghu mine103working face; after digging the roadway and gob-side entry retaining, the peak stresses in the roof and the coal side increase with the increasing of the depth and the roadway cross section; and the position of the peak stress is gradually away from the roadway; the surrounding rock deformation and the average vertical stress of the filling body also increase linearly with the increasing of the depth and the roadway cross section, which indicates that the buried depth is much more deeper and the roadway section is much bigger, gob-side entry retaining is much more difficult to support, strength requirement of the filling body is much higher.2) Influence factors of gob-side roadway surrounding rock deformation are analyzed from aspects of technology and geology in detail; by using the orthogonal numerical simulation method, the influence factors of surrounding rock deformation of gob-side entry retaining are analyzed, results show that the mining height has the greatest influence on the roof subsidence, and the coal strength and mining depth plays a secondary role on it; the floor strength has the greatest influence on the floor heave, and floor heave increases with the decrease of floor strength; the coal strength has the greatest influence on the horizontal displacement and plastic zone width of coal, and they increases with the decrease of coal strength.3) Based on the concept of the inner and outer structures of gob-side entry retaining, the whole mechanical model of the inner structure in gob-side entry retaining is established, and on this basis, the mechanical model of immediate roof, filling body, coal sides and the floor are established; according to the incremental equilibrium equation of energy and work of immediate roof, the stability criterion of immediate roof can be obtained, so the relationship between the stability of direct roof and roadway width, the inside support resistance, the outside support resistance and other factors are analyzed; by using the variational principle of displacement, calculation formula of immediate roof subsidence was obtained, and the relationship between it and roadway width, the inside support resistance, the outside support resistance and other factors are analyzed; according to the incremental equilibrium equation of energy and work of immediate roof, the minimum supporting force of the filling body to sustain the stability of immediate roof is obtained, the calculation results show that:it increases with increase of the roadway width; according to the roadway floor heave mechanism of gob-side entry retaining, the mechanics model of floor deformation in gob-side entry retaining is established, and by using the principle of minimum potential energy, deformation formula of the floor in gob-side entry retaining is derived.4) Based upon activity law of overlying strata and the characteristics of rock deformation and failure of the gob-side entry retaining with large section in deep mines at different stage,"Classification stage supporting, the high strength and low density support, support matching and coordination, roadway deformation minimization before mining and long-term stability, reinforced support in key position, the same important of safety effect, efficiency and benefits" are put forward.