Study On The Evolvement Law And Control Technology Of Rock Deformation Around The Gob-Side Entry Of Fully Mechanized Top-Coal Caving Faces In Deep Mines

It is one of the difficult and hot research issues in the fields of coal mining and rock mechanics to study the support of gob-side entries in deep mines. At present some research progresses have been made on the failure mechanism of gob-side entries in deep mines. However, the existing research findings still are incomplete due to the complexity of the research issues. For example, there are few research findings on the evolvement law of rock deformation around the gob-side entry of fully mechanized top-coal caving faces in deep mines.Funded by the National Natural Science Foundation of China (Grant No. 50490273,50674083) and taking the gob-side entry of 14309 Mining Face of Dongtan Colliery as the engineering background, this dissertation makes deep and systematic research on the evolvement law and control technology of rock deformation around the gob-side entry of fully mechanized top-coal caving faces in deep mines. Based on the research achievement made by former scholars, this paper mainly deals with the evolving process of stress and displacement of rocks around deep gob-side entries by means of physical and numerical simulation, theoretical resolution and in-situ measurement.(1) Based on the theory of key strata and elasto-plastic mechanics, the behavior of overburden strata and the deformation mechanism of surrounding rocks of deep gob-side entries are theoretically analyzed. The mechanical models of key stratum and surrounding rocks are established, and the analytical formulas that reflect the stability of key triangular rock block and the stress and displacement of surrounding rocks are derived. The stability mechanism of the surrounding rocks is deeply analyzed under the engineering background of the gob-side entry of 14309 Mining Face. Furthermore, the main influencing factors of surrounding rock stability and their interrelation are analyzed.(2) The performance of three common support structures in coal mines is investigated by physical simulation on two test beds. Under the conditions of different mining depths and pillar widths, the effect of the support structures on the stress and displacement of surrounding rocks is analyzed and the mechanical mechanisms of active and passive support structures are discussed. After analyzing the support function of bolting with bar, wire mesh and cable, the mechanism of action of cable and its uses are obtained, and the technical idea of high-intensity integral support is proposed.(3) Using the software FLAC3D, numerical simulations are made to study the evolvement law of stress and displacement of surrounding rocks under conditions of different pillar widths and mining depths. The changing law of surrounding rock stability with influencing factors is achieved. The new thought of"resisting, reinforcing, pressure-reliving"and the new viewpoint of"process control"and"dynamic double support"for the rock deformation control of deep gob-side entries are put forward.(4) According to the actual conditions of the gob-side entry of the 14309 Mining Face, the rational width of coal pillar is determined to be 4m, and the reasonable support scheme is designed which includes primary supporting with bolt, bar, wire mesh and cable, secondary reinforcing by grout injection, dynamic pressure relief and advance roof strengthening. During the process of drivage and coal mining, the rock stress and displacement of the gob-side entry and the anchorage force of bolts are monitored. The monitored results show that the rock deformation of the entry is well controlled, through which the safe and high-efficiency production is realized and technical and economic benefits are made. Therefore, the research findings of this dissertation are proved to be practical and reliable.