| Coal resources are the main mineral resources in China.With the development of highly centralized coal mining groups and super large coal bases,new requirements are put forward for the coal mining lifting system.The shaft structure is the "throat" part of the coal lifting system,and its safe and efficient operation is the key to the coal mining operation.At present,large-scale coal mining bases have been built in Western China.Inclined shaft or inclined shaft and vertical shaft are mostly used for lifting and transporting.The stratum crossed by inclined shaft is mainly sandstone stratum,which has the characteristics of large thickness,weak rock layer,poor cementation,strong softening and strong water yield.Under the coal mining operation,the inclined shaft will be subject to "follow-up phenomenon" due to stratum settlement,Moreover,due to the consolidation and compression of stratum,it will produce "encircling" effect,and produce additional stress on the inclined shaft wall,which will bring hidden danger to the safe service of inclined shaft.Based on the national science and technology support project of "Research on the influence of coal seam mining on the stability of inclined shaft segment structure(subject No.: 2013ba10b06)",this paper takes the shield tunneling inclined shaft project of Taigemiao coal mine in Xinjie of Shenhua Group as the background,and takes the downward vertical additional force caused by stratum drainage effect on the outer wall of shaft as the enlightenment,which leads to the fracture accident of shaft wall structure Through the analysis of indoor rock physical and mechanical tests,the functional relationship between the axial deformation of sandstone and pore water pressure drop is constructed,and the calculation method of drainage settlement of water bearing strata is proposed.Secondly,through theoretical calculation,the differential equation of inclined shaft deformation and the analytical calculation method of inclined shaft segment stress and deformation are established.The paper further studies the fluid structure coupling similar model test method,and establishes the calculation model The model test method of porous water bearing sandstone formation is established to simulate the formation settlement caused by dewatering and drainage in deep water rich sandstone formation and its influence on inclined shaft structure.Finally,the additional stress increment of inclined shaft segment structure before and after dewatering and drainage in water rich sandstone formation is studied by numerical simulation method,and the change of safety factor of inclined shaft segment structure is calculated The research results are as follows:(1)Through rock micro analysis and physical and mechanical test analysis,it is proved that Cretaceous and Jurassic sandstones are porous and non compact rocks,and have consolidation compression characteristics.Through sandstone drainage consolidation test,the exponential function relationship between compression deformation and water head pressure drop of Cretaceous and Jurassic sandstones is obtained,and on this basis,the water bearing zones of Cretaceous and Jurassic sandstones are constructed By comparing the results of fluid structure coupling numerical simulation and linear elastic theory,the paper puts forward the fitting formula calculation method,which considers the variation of mechanical parameters of the formation with the dissipation of head pressure,and is more suitable to calculate the drainage settlement of sandstone aquifer.(2)Based on the elastic foundation beam theory,the elastic foundation beam model of shield inclined shaft segment structure under non-uniform load in surface soil water bearing stratum and bedrock water bearing stratum is constructed,and the differential equation of inclined shaft structure deformation is derived.According to the differential equation of inclined shaft deformation and the equivalent continuous stiffness model of inclined shaft segment,the solution of inclined shaft segment stress and deformation is derived by taking bolts as bearing nodes Based on the calculation method of drainage settlement of sandstone formation,the deflection of inclined shaft and the additional stress acting on the segment structure are calculated by using the derived formula,and the safety of the segment structure is evaluated.(3)A fluid structure coupling model test bed based on large-scale model test loading system is developed,and a similar model test is carried out on the formation settlement caused by dewatering and drainage in deep water rich sandstone formation and its influence on inclined shaft structure.Through the test,the formation settlement caused by dewatering and drainage in deep water rich sandstone formation and the differential settlement rules of different aquifers are found,as well as the factors affecting the structure of inclined shaft According to the variation law of longitudinal and circumferential additional bending moment and axial force of inclined shaft section caused by layer settlement,the safety factor of inclined shaft segment structure section before and after drainage is calculated by safety factor evaluation method.(4)Taking the drainage settlement of sandstone stratum as the boundary condition,the displacement of inclined shaft caused by stratum settlement and the additional stress and bending moment acting on the inclined shaft segment are analyzed by numerical simulation method under the action of drainage through Cretaceous aquifer and Jurassic aquifer The safety factor of inclined shaft segment structure section before and after drainage is calculated.It is concluded that the inclined shaft segment concrete is mainly controlled by compression,and the most unfavorable segment is the arch waist in the aquifer.(5)By comparing the results of theoretical calculation method,similar model test method and numerical simulation method of inclined shaft segment stress and deformation,the consistency of the three research methods in the overall deformation law of inclined shaft structure,the variation law of additional stress and additional bending moment is verified.It is concluded that the curvature radius of the overall displacement of inclined shaft is 105 m after the drainage of Cretaceous aquifer and Jurassic aquifer,which is the same as that of the other two methods The increment of additional bending moment is greater than that of additional axial force,and the increment of additional bending moment is the largest at the arch waist. |
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