Investigation On Mechanical Properties Of Double-layer Lining Structure In Long-distance Shield Water Conveyance Tunnel

With the rapid development of urban economy,the problem of urban water use is becoming more and more serious.To effectively solve this problem,cross-regional water transfer project is a flexible and reliable solution.In this paper double-layer lining structure of shield tunnel was taken as research object,in-situ test and numerical simulation of structure were carried out.Accroding to monitoring data,lining structure stress-deformation reponse under external water and earth pressures was preliminarily analyzed.On this basis,a threedimensional refined model was established,by using finite element method.Based on model,deformation and mechanical characteristics of double-layer lining structure were analyzed under different internal pressure,geological conditions and prestressing measure application,which provided theoretical guidance and technical support for double-layer lining structure design in long-distance water conveyance tunnel.The main work and achievements of this article are summarized as follows:(1)The engineering geology and structural design of the in-situ test are briefly described.Based on the monitoring data,a preliminary analysis stress state of outer liner segments is carried out.Furthermore,a three-dimensional finite element model of entire segment is established.Results of model calculation are in good agreement with monitoring data,which verifies model rationality.(2)Double-layer composite lining is established to analyzing mechanical response and deformation characteristic of structural system,When internal pressure range 0.0 to 0.8MPa.According to anslysis results,operating internal pressure should not exceed 0.4MPa.(3)By studying circumferential deformation,joint opening and bolt stress of segment,sensitivity of the surrounding rock parameters was analyzed.Results show that for a single surrounding rock,surrounding rock restraint effect decreases with increasing surrounding rock strength.For upper soft lower hard,it is not conducive to deformation of structural system with difference in surrounding rock increasing.(4)The influence of prestressing measures on structural system mechanical properties was analyzed preliminarily.When internal water pressure exceeds 0.35 MPa,prestressing measures should be considered to improve structure load-bearing capacity.