Abstract: A discrete element method for modelling fracture evolution of roadway surrounding rock is provided, which includes: taking rock cores from a coal seam in the field and recording RQD values, observing roadway deformation, and making a statistical analysis on distribution characteristics of fractures in the coal seam; testing mechanical parameters of coal-rock samples indoors, and calculating strength of a rock mass according to the RQD values; creating a numerical model by using a UDEC-Trigon module to adjust the parameters to match the strength of the rock mass, and correcting model parameters; and creating a numerical model of an engineering scale to adjust the parameters to match field deformation characteristics, and finally simulating fracture evolution of the roadway surrounding rock. The present invention provides accurate and basic mechanical parameters for discrete-element numerical simulation of roadway deformation, guaranteeing realistic and reliable simulation results.

Abstract: A discrete element method for modelling fracture evolution of roadway surrounding rock is provided, which includes: taking rock cores from a coal seam in the field and recording RQD values, observing roadway deformation, and making a statistical analysis on distribution characteristics of fractures in the coal seam; testing mechanical parameters of coal-rock samples indoors, and calculating strength of a rock mass according to the RQD values; creating a numerical model by using a UDEC-Trigon module to adjust the parameters to match the strength of the rock mass, and correcting model parameters; and creating a numerical model of an engineering scale to adjust the parameters to match field deformation characteristics, and finally simulating fracture evolution of the roadway surrounding rock. The present invention provides accurate and basic mechanical parameters for discrete-element numerical simulation of roadway deformation, guaranteeing realistic and reliable simulation results.

Abstract: A prefabricated stair modular assembly mold comprises a base, a step standard module, an upside module of a lower platform, an underside rotating module of a lower platform, an upside module of an upper platform, an underside rotating module of an upper platform, an underside common module, and an underside adjustment modules. Prefabricated stair molds of different dimensions are formed by means of locating holes provided in the assembling modules, and are then fixed by means of sliding holes at two ends. Further disclosed is a mounting method for said assembly mold. Said assembly mold has high positioning accuracy, and small accumulated error, improving the mounting efficiency of the prefabricated staircase mold.

Abstract: The present invention discloses a blind bolt fastening device, and belongs to the technical field of bolts. The blind bolt fastening device includes Z-shaped gaskets, a fixed plate, elastic hinges, a screw cap, a nut, an integrated gasket and the like. The top end of the screw cap is connected to the fixed plate in a spot welding manner. A plurality of elastic hinges is uniformly mounted on the fixed plate. One end of each elastic hinge is rotatably fixed on the fixed plate. Connection points of the elastic hinges and the fixed plate do not exceed the outer edge of the fixed plate. The other end of each elastic hinge is connected to one Z-shaped gasket in a spot welding manner. In an initial state, the plurality of Z-shaped gaskets are uniformly distributed and fitted onto the outer wall of the screw cap along a circumferential direction.

Abstract: A prefabricated stair modular assembly mold comprises a base, a step standard module, an upside module of a lower platform, an underside rotating module of a lower platform, an upside module of an upper platform, an underside rotating module of an upper platform, an underside common module, and an underside adjustment modules. Prefabricated stair molds of different dimensions are formed by means of locating holes provided in the assembling modules, and are then fixed by means of sliding holes at two ends. Further disclosed is a mounting method for said assembly mold. Said assembly mold has high positioning accuracy, and small accumulated error, improving the mounting efficiency of the prefabricated staircase mold.

Abstract: An apparatus for protecting a roof tray when a gob-side entry retaining end support migrates is provided. The apparatus is mounted at a top end position of a hydraulic support, and includes a movable bearing mechanism, an automatic expansion/contraction connecting groove mechanism, and an active reset mechanism. The movable bearing mechanism includes two parallel belts and a plurality of rollers supporting the belts, and the rollers are mounted on and supported by a bearing mechanism. The automatic expansion/contraction connecting groove mechanism is two concave base plates fixed between the two belts, and the two concave base plates are spaced by a distance. The active reset mechanism includes two telescopic rods and reset springs sleeved on the telescopic rods, and the telescopic rod is connected to an end portion of the reset spring to form a synchronous mechanism.

Abstract: The present invention discloses a blind bolt fastening device, and belongs to the technical field of bolts. The blind bolt fastening device includes Z-shaped gaskets, a fixed plate, elastic hinges, a screw cap, a nut, an integrated gasket and the like. The top end of the screw cap is connected to the fixed plate in a spot welding manner. A plurality of elastic hinges is uniformly mounted on the fixed plate. One end of each elastic hinge is rotatably fixed on the fixed plate. Connection points of the elastic hinges and the fixed plate do not exceed the outer edge of the fixed plate. The other end of each elastic hinge is connected to one Z-shaped gasket in a spot welding manner. In an initial state, the plurality of Z-shaped gaskets are uniformly distributed and fitted onto the outer wall of the screw cap along a circumferential direction.