Mechanical Behavior Of Segment Lining In Coal Mine Inclined Shaft

Along with rapid development of national economy,coal energy consumption increases with the years,which makes coal mined in a deeper depth.Currently,the first selected method of deep-buried coal tunnel excavation is the more safety and efficient Tunnel Boring Machine(TBM)method,which is combined with inclined shaft to rapidly reach the mining face.When TBM method is selected to excave inclined shaft in deep rock mass under the high geostress conditions,there are two intractable probloms in the process of design and construction.The first trouble is how to efficiently reduce the plastic deformation pressure applied on segments,and the other is how to make sure the long-term safety of tunnel constructed in soft rock mass with a significant creep effect.Based on the long inclined shaft by TBM method in Taigemiao,Xinjie and combined with the project named "Fundamental research on design theory of coal mine roadway(inclined-shaft)lining structures constructed by TBM(shield machine)in complex condition"from Coal United Foundation,this thesis analyses the stress and displacement in surrounding rock considering the strain softening,explore the reasonable lag grouting distance and research the influence of creep in surrounding soft rock on deep-buried tunnel.The results from this research can provide reference for similar engineering.The main contents and conclusions from this thesis are as follows:(1)The solution of displacement,stress and plastic zone in surrounding rock,under the condition that the circular tunnel is loaded by non-axisymmetrical initial geostress,can be analitically deducted based on the strainsoftening model.The results show that the radius of plastic zone deducted above is bigger than the one based on the ideal elastoplastic model,but two model has the same distribution rule of plastic zone.Then the softening influence of cohesion,internal friction angle and dilation angle on rock displacement,plastic zone radius and segment stress is explored by simulating the surrounding rock with embedded"strainsoftening model" in FLAC3D software.The results indicate that rock displacement,plastic zone radius and segment stress increase with the increased softening degree,which proves that it is essential to consider the strain softening effect in deep-buried tunnel with soft surrounding rock.(2)The excavation and support procedure in tunnel construction by single shield TBM,adopting the construction technology of compressible layer,are simulated by FLAC3D finite difference software,in which the surrounding rock is modelled by embedded"strainsoftening model" in FLAC3D software.The influence of lag grouting distance on the rock displacement and segment stress is explored.The results show that rock displacement and segment stress increase with the increased lag grouting distance of grave layer.Then the shortest lag grouting distance is the one when maximum of first principal stress is firstly lower then the design strength of segment concrete,while the reasonable lag grouting distance is the one when the growth rate of rock displacement significantly decreases.Afterwares,the reasonable lag grouting distance of grave layer for tunnel constructed in different depth is reached.(3)The effect of rock creep on deep-buried tunnel surrounding by soft rock is numerically studied by adopting the constitutive model of visco-elastic-plastic Burgers embedded in FLAC3D.The change of displacemet in surrounding rock and segment stress with creep time within 100 years after tunnel construction is explored to evaluate the long-term safety of tunnel,after which the tunnels in different depths and different lateral pressure coefficients are studied using similar method.