Safety Control And Effect Evaluation Of Surrounding Rock In Roof Cutting Roadway In Lvtang Coal Mine

The S204 working face of the 6th middle layer of Lvtang Coal Mine is mined by the topless unloading and non-coal pillar technology along the empty roadway.This technology has many advantages such as reducing the amount of roadway excavation,multiple use of retaining lanes,and changing ventilation.In this paper,the law of overlying strata movement in the cut-out roadway is qualitatively analyzed.The FLAC3D is used to simulate the bearing pressure changes in different directions of the working face and the support effect of the roadway.The field test data is used to explore the surrounding rock variation trend of the roadway.The research content mainly has the following four aspects:(1)The roof structure model of the cutting roof is established,and the law of the movement of the top side of the slit is systematically analyzed.Due to the influence of the slit,the top side of the slit is more broken and can be quickly connected.The overburden is supported,so the contact point of the overlying strata on the slit side will move up compared to the uncut side.In order to quantitatively calculate the roof of the roadway,the "small structure" model of the roof of the roadway is established.The calculation formula of the subsidence is formed according to the work of the roof and the support body and the strain energy of the surrounding rock.(2)Through the numerical simulation,the distribution law of the bearing pressure in front of and behind the working face when cutting the roof is studied.The supporting pressure in front of the working face will be transferred to the solid coal in the roadway.The roof of the empty roadway has been formed by pre-splitting blasting.The surface is cut so that the supporting pressure in front of the working surface cannot be transferred to the solid coal side of the roadway.On-site measurement of the bracket pressure found that the pressure of the bracket near the slit side is smaller than that of the uncut side bracket,and the pressure of the middle bracket is greater than the pressure of the brackets at both sides.(3)According to the different changes of the structure of the constant-resistance anchor cable,it is divided into three stages.the constant-resistance anchor cable will produce different changes.When the anchor cable is forced to reach the constant resistance value,The constant resistance body is sliding friction in the sleeve,and the lock is retracted and the sleeve is radially expanded.At this time,the force of the constant resistance device does not change any more,and the lock and the constant resistance body and the constant resistance sleeve show displacement.The displacement is adapted to the large deformation of the surrounding rock,and the use of the constant-resistance anchor cable can play an active role,effectively reducing the amount of subsidence of the roadway,and the force of the constant-resistance anchor cable on the side of the goaf is greater than that of the central constant-resistance anchor cable.(4)Through the monitoring of the amount of movement of the top and bottom of the roadway,the force of the anchor cable,the pressure and the shrinkage of the single pillar,and the monitoring of the force the dam,the monitoring results show that the S204 working face of the 6th middle layer of Lvtang coal mine is influenced by ahead of the support.The influence range of pressure in the front of working face is 30?35m and the range between 0m and 40m on the behind of working face is severe,and the deformation of the monitoring surface of 40?80m is slowed down.When it is 80m behind the working face,the monitoring data basically does not occur variety.