Study On Mechanical Chracteristics Of Inclined Shaft Lining In Deep Alluvium

Since cylindrical shaft lining possesses excellent mechanical behavior and structural stability,it is widely used in various types of underground space developments in geotechnical engineering.Many research studies concerning this structure are carried out both at home and abroad,however,the studies on spatial stress law of inclined shaft lining are relevantly small when the axis of the shaft lining has an inclined angle with the direction of gravity.This paper conducted a research on the spatial evolution of stress in topsoil inclined shaft lining with the application of both the theoretical analysis and model test.Based on the results,the influence of the axial inclination angleaon the spatial evolution of stress in the inclined shaft lining and the corresponding mechnism are studied in this paper.Moreover,the calculated methods for the thickness and the freezing parameter of the freezing walls in inclined shafts are proposed.First of all,according to the principle of static balance,the paper took the influence of axial dip angleainto consideration,deducing three calculated formulas for spatial distribution of radial load qr,ring shear load qrq,and axial shear load qrz in inclined shaft lining.In terms of the special cases when the axial dip anglea=90°ora=0°,the formulas to transform to loading calculated methods in vertical shaft and horizontal circular tunnel.Applying the dimensionless analysis method,the influence of dip angle on the spatial evolution of external load of inclined shaft lining and the corresponding mechnism are studied.Furthermore,the influence of size effects on three external loads are taken into consideration.Secondly,based on the theory of elasticity and static equilibrium and the principle of elastic superposition,this paper took the influence of axial dip angleainto consideration,constructing a mechanical model of inclined shaft lining considering 3 external loads including radial load qr,ring shear load qrq,and axial shear load qrz,and thus deducing the analytical solution of stress.In terms of the situation when axial dip anglea=90°,the formula transforms to Lamech solution.Applying the dimensionless analysis method,the effects of the axial dip angleaon spatial evolution of the stress distribution of inclined shaft lining and the coreespoding mechnism are studied.Furthermore,the influence of size effects on stress distribution is considered.Addtionally,a three-dimensional photoelastic stress freezing test system for underground structures is self-designed,a multi level parallel lever loading system is used for loading application,and the multi linearly incremental surface load was applied to model the increased overburden pressure on inclined shaft lining with increasing depth.Through several experiments,the fabrication process of the three-dimensional(3D)photoelastic model of the shaft lining was finished,and the3D shaft lining model was designed and developed.Based on similarity theories,3D photoelastic stress freezing model test for inclined shaft lining is achieved and the distribution of the isometric line of inclined shaft lining is obtained,which can intuitively reflect the structural strength margin.By comparing the experimental results with the theoretical analysis results,the reliability of the theoretical results can be verified.Finally,following the above results and combining with the existing calculation methods of formation pressure,the design theory and method of inclined shaft lining for multi-type formation conditions such as weak permeable clay layer,permeable sand layer and deep buried stratum are established with considering the special external load characteristics of inclined shaft lining.The corresponding methods contribute for the design of a thick surface soil inclined shaft lining in a more economy,effective and reliabe way.