Experimental Research On The Supporting Mechanism Of Corrugated Steel Initial Support And The Mechanical Performance Of Joints In Mined Tunnels

China is in the era of great development of underground space,and the development and utilization of underground space is in full swing throughout the country.With the disappearance of the demographic dividend,the shallow tunnel construction method is changing to mechanized large-section construction.It is urgent to seek a support structure that can be closed into a ring in time and has high early strength.The corrugated steel structure just meets this feature.This paper studies the supporting mechanism,block method,joint mechanical properties and waterproof performance of corrugated steel used as the initial support structure of the tunnel with the combination of laboratory test,numerical simulation and theoretical analysis.The main research contents and research results are as follows:(1)The supporting mechanism of corrugated steel used as the initial support structure of the tunnel was revealed.The influence of grouting material strength and tunnel over-excavation range on the safety of corrugated steel initial support structure was discussed by the convergence-confinement method.The similarities and differences of three initial support structures of corrugated steel,grille and steel arch were compared by numerical simulation.The influence of hardening process of grouting material and grouting pressure on formation disturbance control and initial support structure deformation was explored.(2)The safety changes of corrugated steel initial support structure with different block methods were summarized.By means of numerical simulation,the safety changes of the corrugated steel initial support structure when divided into blocks according to the minimum bending moment position,the maximum bending moment position and the combination method were studied.The internal force distribution of the original structure is less affected when the minimum bending moment position is used to divide the block.The internal force distribution of the original structure is adjusted to a certain extent when the maximum bending moment position and the combination method are used to divide the block.(3)The mechanical behavior performance of common corrugated steel joints and the optimization design priority of corrugated steel parameters were revealed.Through laboratory tests,the bending stiffness of three joint types of lap joint,flat flange and back reinforced flange was studied,and the sensitivity analysis of the influence of waveform parameters on the mechanical properties of the two joints of lap joint and flat flange was carried out.The entropy weight method was used to analyze the optimal design of corrugated steel parameters and joint type matching.(4)The relationship curves between the ultimate water pressure and the bolt pretightening force of the commonly used corrugated steel rubber pad were established.Through the laboratory waterproof test,The relationship between the bolt pre-tightening force and the ultimate water pressure was studied when the corrugated steel flat flange joint was equipped with three different rubber gaskets: ordinary water-swellable rubber gasket,special-shaped water-swellable rubber gasket and EPDP water-swellable rubber gasket.The waterproof performance of corrugated steel flat flange and lap joint was compared.