In order to solve the difficult conditions of soft rock,water-trickling and hard-maintain of main air-return roadway in Tarangaole Colliery,high pretensioned stress and intensive bolt-shotcrete support program was des...In order to solve the difficult conditions of soft rock,water-trickling and hard-maintain of main air-return roadway in Tarangaole Colliery,high pretensioned stress and intensive bolt-shotcrete support program was designed and mechanical property of shotcrete layer was specially monitored through utilizing a type of concrete stress meter with oscillating chord after the program was carried out.It was indicated that,due to rock pressure and support resistance,the interior of shotcrete layer would emerge diverse stresses in axial,radial and tangential directions.With time passing internal stresses in three directions,whose average values were-0.061,0.043 and 0.517 MPa respectively,fluctuated first and then tended to stability slowly.The axial and radial stresses were relatively smaller than tangential stress which was 11,12 times the two formers respectively.Along the section of roadway,axial and tangential stresses distributed symmetrically and increased gradually from the top of arch to the waist of wall,but reduced at the foot of wall.Radial stresses reduced from the top of arch to the waist of arch first,and then increased in the waist of wall.Axial stresses were tensile substantially,except for stresses in arch vault tending to compressive,but all the radial stresses were compressive.Nevertheless,tangential stresses in the wall were compressive and tangential stresses in the arch were tensile.During the period of roadway excavating,the stress of shotcrete layer was less than its ultimate bearing capacity,with no significant stress concentration.At the end of this article,some suggests are given to shotcrete support design.展开更多
Severe gas disasters in deep mining areas are increasing,and traditional protective coal seam mining is facing significant challenges.This paper proposes an innovative technology using soft rock as the protective seam...Severe gas disasters in deep mining areas are increasing,and traditional protective coal seam mining is facing significant challenges.This paper proposes an innovative technology using soft rock as the protective seam in the absence of an appropriate coal seam.Based on the geological engineering conditions of the new horizontal first mining area of Luling Coal Mine in Huaibei,China,the impacts of different mining parameters of the soft-rock protective seam on the pressure-relief effect of the protected coal seam were analyzed through numerical simulation.The unit stress of the protected coal seam,which was less than half of the primary rock stress,was used as the mining stress pressure-relief index.The optimized interlayer space was found to be 59 m for the first soft-rock working face,with a 2 m mining thickness and 105 m face length.The physicochemical characteristics of the orebody were analyzed,and a device selection framework for the soft-rock protective seam was developed.Optimal equipment for the working face was selected,including the fully-mechanized hydraulic support and coal cutter.A production technology that combined fully-mechanized and blasting-assisted soft-rock mining was developed.Engineering practices demonstrated that normal circulation operation can be achieved on the working face of the soft-rock protective seam,with an average advancement rate of 1.64 m/d.The maximum residual gas pressure and content,which were measured at the cut hole position of the protected coal seams(Nos.8 and 9),decreased to 0.35 MPa and 4.87 m^3/t,respectively.The results suggested that soft-rock protective seam mining can produce a significant gas-control effect.展开更多
Large deformations such as roof subsidence,floor heave,and two-sided deformations occur frequently in deep soft-rock roadways.The deformation becomes more severe under the combined effect of high in-situ and mining-in...Large deformations such as roof subsidence,floor heave,and two-sided deformations occur frequently in deep soft-rock roadways.The deformation becomes more severe under the combined effect of high in-situ and mining-induced stresses,which detrimentally affect the safe mining of coal.Based on the geological conditions and roadway failure characteristics of the Nanyaotou coal mine in Shanxi province,China,we used comprehensive numerical simulations and field observations to study roadway deformation and failure.The deformation mechanism of deep soft-rock roadways under dynamic pressures is described,and the corresponding control measures are proposed.The deformation and fracture development characteristics of roadways surrounding rocks were explored with a primary support scheme,and its effects were evaluated.The radius of the plastic zone and the displacement deformation of the roadway were studied by using theoretical analysis,and a combined-support design of‘‘anchor bolt+anchor cable+shotcrete+deep and shallow borehole grouting+inverted arch”was proposed to limit deformations and relieve the stress in the surrounding rocks.Numerical simulations and field monitoring showed that the combined support scheme can effectively mitigate the large deformations of ventilation roadways and provide guidance for the stable control of deep soft-rock roadways.展开更多
文摘In order to solve the difficult conditions of soft rock,water-trickling and hard-maintain of main air-return roadway in Tarangaole Colliery,high pretensioned stress and intensive bolt-shotcrete support program was designed and mechanical property of shotcrete layer was specially monitored through utilizing a type of concrete stress meter with oscillating chord after the program was carried out.It was indicated that,due to rock pressure and support resistance,the interior of shotcrete layer would emerge diverse stresses in axial,radial and tangential directions.With time passing internal stresses in three directions,whose average values were-0.061,0.043 and 0.517 MPa respectively,fluctuated first and then tended to stability slowly.The axial and radial stresses were relatively smaller than tangential stress which was 11,12 times the two formers respectively.Along the section of roadway,axial and tangential stresses distributed symmetrically and increased gradually from the top of arch to the waist of wall,but reduced at the foot of wall.Radial stresses reduced from the top of arch to the waist of arch first,and then increased in the waist of wall.Axial stresses were tensile substantially,except for stresses in arch vault tending to compressive,but all the radial stresses were compressive.Nevertheless,tangential stresses in the wall were compressive and tangential stresses in the arch were tensile.During the period of roadway excavating,the stress of shotcrete layer was less than its ultimate bearing capacity,with no significant stress concentration.At the end of this article,some suggests are given to shotcrete support design.
文摘Severe gas disasters in deep mining areas are increasing,and traditional protective coal seam mining is facing significant challenges.This paper proposes an innovative technology using soft rock as the protective seam in the absence of an appropriate coal seam.Based on the geological engineering conditions of the new horizontal first mining area of Luling Coal Mine in Huaibei,China,the impacts of different mining parameters of the soft-rock protective seam on the pressure-relief effect of the protected coal seam were analyzed through numerical simulation.The unit stress of the protected coal seam,which was less than half of the primary rock stress,was used as the mining stress pressure-relief index.The optimized interlayer space was found to be 59 m for the first soft-rock working face,with a 2 m mining thickness and 105 m face length.The physicochemical characteristics of the orebody were analyzed,and a device selection framework for the soft-rock protective seam was developed.Optimal equipment for the working face was selected,including the fully-mechanized hydraulic support and coal cutter.A production technology that combined fully-mechanized and blasting-assisted soft-rock mining was developed.Engineering practices demonstrated that normal circulation operation can be achieved on the working face of the soft-rock protective seam,with an average advancement rate of 1.64 m/d.The maximum residual gas pressure and content,which were measured at the cut hole position of the protected coal seams(Nos.8 and 9),decreased to 0.35 MPa and 4.87 m^3/t,respectively.The results suggested that soft-rock protective seam mining can produce a significant gas-control effect.
基金supported by the Key Projects of the Joint Fund of the National Natural Science Foundation of China(Grant No.U21A20107)the National Natural Science Foundation of China(Grant No.52074239)+1 种基金The financial support by the National Research Foundation of Korea(Grant Number:NRF-2021R1A2C3011490)also greatly appreciated.
文摘Large deformations such as roof subsidence,floor heave,and two-sided deformations occur frequently in deep soft-rock roadways.The deformation becomes more severe under the combined effect of high in-situ and mining-induced stresses,which detrimentally affect the safe mining of coal.Based on the geological conditions and roadway failure characteristics of the Nanyaotou coal mine in Shanxi province,China,we used comprehensive numerical simulations and field observations to study roadway deformation and failure.The deformation mechanism of deep soft-rock roadways under dynamic pressures is described,and the corresponding control measures are proposed.The deformation and fracture development characteristics of roadways surrounding rocks were explored with a primary support scheme,and its effects were evaluated.The radius of the plastic zone and the displacement deformation of the roadway were studied by using theoretical analysis,and a combined-support design of‘‘anchor bolt+anchor cable+shotcrete+deep and shallow borehole grouting+inverted arch”was proposed to limit deformations and relieve the stress in the surrounding rocks.Numerical simulations and field monitoring showed that the combined support scheme can effectively mitigate the large deformations of ventilation roadways and provide guidance for the stable control of deep soft-rock roadways.
