Research On The Mechanism Of Floor Heave And Its Anchor Pile Control In Roadway With High Stress Soft Floor

The joints and fissures of the surrounding rock of the roadway with a soft floor develop rapidly,and have the characteristics of low strength,weak bearing capacity and poor stability,so the roadway usually shows serious deformation characteristics of the floor,especially under high stress mining conditions,the floor of the roadway is heaved.phenomenon is particularly strong.Therefore,the research on the mechanism characteristics and stability control of the floor heave in the roadway with high stress soft floor is of great significance to the treatment of the floor heave in the roadway with high stress soft floor.This paper takes a gas drainage roadway in the 4(3+4)# coal seam of Shuangliu Coal Mine as the engineering research background,aiming at the high stress characteristics of the surrounding rock of the roadway under the influence of mining and fault structure,combined with the sliding failure characteristics of the soft rock floor,through mechanical analysis The mechanism of the tunnel kick drum is analyzed.On the basis of theoretical analysis,a bottom drum control and governance scheme is proposed by adding two sets of cable-stayed anchor cables and adding bottom steel sheet piles,and numerical simulation is used for experimental verification.The field application test shows that the stability monitoring results show that the field application effect under the support of the optimized scheme is good,thus providing a scientific basis for the pile-anchor control technology of the roadway with the soft floor in the high stress area.The main research conclusions are as follows:(1)The buried depth of a certain gas drainage roadway in the 4(3+4)# coal seam reaches500 meters.Due to the influence of the tectonic stress of the nearby fault and the mining operation of the adjacent working face,the roadway as a whole is in a high stress area.Laboratory X-ray diffraction analysis of its floor mudstone shows that the roadway floor is weak in cementation and strong in expansion,resulting in low tensile strength.In a high stress environment,the roadway floor is prone to plastic extrusion failure,and an extrusion flow bottom occurs.drum.(2)Squeeze-flow type bottom drum is the phenomenon of dislocation and slippage of the rock mass directly broken at the bottom of the roadway under the action of stress.The study on the principal stress characteristics of the surrounding rock of the floor shows that: when the horizontal stress is perpendicular to the direction of the maximum principal stress,the roadway is most severely damaged;when the horizontal stress is parallel to the direction of the maximum principal stress,the roadway is damaged less,and the roadway supports The effect is better.By establishing a mechanical model of the surrounding rock of the roadway and carrying out theoretical calculations,the analysis shows that the tectonic stress of the fault causes the horizontal stress of the surrounding rock of the roadway to increase by 2.1 times,and the influence of mining stress causes the vertical stress of the surrounding rock of the roadway to increase by 2.1 to 3.5 times.The increase directly leads to the increase of2.45～2.91 times of the sliding destructive force of the roadway floor heave,which aggravates the roadway floor heave phenomenon.(3)According to the analysis of the mechanics mechanism of the kick drum,a kick drum control scheme of adding two sets of cable-stayed anchor cables and adding steel sheet piles at the bottom is proposed,and the original support,two more sets of cable-stayed cables,and the bottom are compared through the numerical simulation test.Compared with the original support scheme,the peak value of vertical stress increased by 22.8%,and the distance between the peak position and the roadway was reduced by 42.2%.%;the peak value of horizontal stress is reduced by 6.9%,and the distance between its peak position and the roadway is reduced by 23.45%;the volume of the floor drum of the roadway is reduced by63.7%,the maximum moving amount of the roof and floor is reduced by 55.7%,and the convergence of the two sides of the roadway is reduced by 60.4%.The plastic failure zone was reduced by 52.4%.The overall stability of the roadway is achieved and the best control effect is achieved.(4)According to the previous experience of the research group and the specific working conditions of the project site,the parameters of the anchor pile support are optimized through the numerical simulation test.From the aspects of economic safety and on-site construction,the best solution is that the distance between the road side cable-stayed anchor cable is 1.5meters from the roof,the length is 6.4 meters,the angle is 40°,the length of the bottom steel sheet piles is 1.2 meters,the row spacing is 1 meter,With an angle of 30°,this scheme has a particularly obvious effect on the stability of the surrounding rock of the roadway.Compared with the original scheme,the convergence of the two sides of the roadway is reduced by65.4%,the floor heave volume of the roadway is reduced by 75.7%,and the plastic failure area is reduced by 72.3%,which realizes the overall stability of the roadway..(5)A field test study was carried out on the optimal scheme in a gas drainage roadway in the 4(3+4)# coal seam of Shuangliu Mine.The monitoring results of mine pressure and roadway displacement showed that the maximum peak load of the bolt was 79.5 k N,which reached 79.5 k N.75.7% of the yield load,the bolt was in good condition during the monitoring period.The maximum peak working load of the roof anchor cable is 139 k N,which is only 27.8% of the yield load of the anchor cable.The maximum peak value of the working load of the cable-stayed cable is 212 k N,which is 42.4% of the yield load of the cable-stayed cable.The stress of the cable-stayed cable is reasonable.After the optimization scheme,the moving amount of the roof and floor is 158 mm,and the convergence of the two sides of the roadway is 179 mm.The overall stability of the roadway is well controlled,and there is no obvious kick drum after the optimization,which verifies the feasibility of the optimization scheme.