Study On The Characteristics Of Overlying Strata Breaking Movement And The Regulation Of Ground Behavior In The Weakly Cemented Soft Rock

With the gradual increase of coal mining depth in the western area,the problems such as serious rib spalling of weakly cemented soft rock,leading floor heave,roof subsidence and and supports drainage are prominent.These factors have a serious impact on the production efficiency and safety of the working face.This paper studies the fracture structure,movement characteristics and ore pressure control of weakly cemented rock overburden on the basis of the law of the ground behaviors in the 11301 first mining face,by using the methods of theoretical inference,similar simulation test and numerical simulation.The main research results are as follows:(1)Through on-site monitoring,the variation of working resistance of hydraulic support are obtained.At the same time,this paper obtains the distribution characteristics of rib spalling in the mining process of 11301 working face.The results show that the caving span of immediate roof in 11301 working face is 9.3～13.9m,the initial weighting step of main roof is 53.7～64.1m,and the periodic weighting step of main roof is 11.9～18.6m.When the working face is in the range of 300～340m,the mining pressure of the working face is high,which is inferred to be caused by the fracture movement of conglomerate strata.(2)Using the method of theoretical derivation,we establish the structural mechanics model of "Transfer rock beam+Rock slab",which considers the roof supporting effect of goaf.The movement structural parameters of conglomerate strata before and after contacting gangue are explored to reveal the main control effect of conglomerate strata on the violent ground behaviors of working face.(3)Through the similar simulation test,the characteristics of roof overburden fracture movement and the evolution law of fracture zone are obtained.It is found that the fracture pattern of the main roof is the same as that of the transfer rock beam,and the fracture of conglomerate strata has the characteristics of bending and sinking first and then breaking.Before the fracture of conglomerate strata,the overburden fracture zone in the working face is trapezoid arch with a height of about 25m.After the conglomerate is broken,the overburden have obvious separation and bending subsidence.The fracture zone extends upward at an angle of 55°.During the fracture of conglomerate strata,the peak and influence range of support pressure in stope reach the maximum,which reflects the main control effect of conglomerate strata on violent ground pressure in stope.(4)Based on the analysis of the influencing factors of the mine pressure appearance in the stope,this paper puts forward the idea of controlling the mine pressure appearance.And the core of idea is pushing mining speed.Then using UDEC software to obtain the influence of the mining speed on the overburden fracture location,this paper puts forward the overburden fracture coefficient ζ,which is used to describe the degree of overburden fracture position entering the goaf.Finally,it is determined that the optimal mining speed of the working face is 10 m/d.The field application and monitoring results show that the mine pressure of the working face after the optimization of the push mining speed is weak.The optimization of push mining speed has played a good role in mining pressure control.