Research On Stress Field Of Deep-buried Subsea Circular Tunnel With Lining Considering Seepage Effect

With the rapid development of my country’s economy and the continuous improvement of comprehensive national strength,the demand for sea-crossing transportation is increasing day by day,and subsea tunnels have received more and more attention.Compared with general mountain tunnels or urban tunnels,subsea tunnels have the characteristics of difficult geological exploration,low arching effect of surrounding rock,and long continuous excavation distance of a single hole,but the biggest difference can be attributed to the difference in groundwater environment.Subsea tunnels are deeply buried in seabed,and there are abundant water sources around the excavation.Groundwater seepage has a great impact on the safety of tunnel surrounding rock and lining structure.Especially under high water pressure conditions,the seepage effect leads to the continuous expansion of the surrounding rock plastic damage zone,which changes the stress state and deformation of surrounding rock and lining structure,and seriously affects the stability and safety of tunnel.Therefore,the study on the stress and deformation of deep-buried subsea tunnels under the influence of seepage effect has important theoretical significance and engineering value.This paper takes the booming subsea tunnels in my country as research background,focuses on the stability of tunnel surrounding rock and lining structure under water-rich conditions,comprehensively adopts the research methods such as theoretical analysis and numerical simulation,and mainly carries out the following research works:(1)Based on consulting a large number of relevant documents at home and abroad,a mechanical model of subsea tunnel including seawater,rock mass and concrete lining is proposed,and the theoretical analysis of seepage field is carried out through the mechanical model.First,the semi-infinite domain including seawater and rock mass elastic zone is mapped into an annular domain by conformal mapping method,and then the seepage equation in polar coordinates between the contact surfaces in mechanical model is established according to the seepage boundary conditions.Finally,it is based on the principle of groundwater hydraulic,the analytical solution formula of the subsea tunnel seepage field is obtained.(2)Through the method of theoretical analysis,the Drucker-Prager(D-P)yield criterion is introduced to describe the elastic-plastic mechanical behavior of subsea tunnel surrounding rock,and the stress field of deep-buried subsea tunnel surrounding rock and lining structure under the influence of seepage effect is carried out.The seepage field obtained in(1)acts on the stress field in the form of body force,and according to the stress boundary conditions in the mechanical model,the stress balance equation of the micro-elements in lining structure and surrounding rock is established.Based on the knowledge of elastic mechanics and the D-P yield criterion,the analytical solution formula of subsea tunnel surrounding rock and lining structure stress field under the influence of seepage effect and the expression of plastic radius is derived.(3)Taking the Shenzhen Mawan Sea-Crossing Passage as an engineering example,numerical simulation is carried out based on ABAQUS finite element software,and the numerical simulation results are compared with the theoretical analysis results in this paper to verify the applicability of mechanical model and the accuracy of theoretical analytical method.In addition,under the influence of seepage effect,the elastic-plastic solution of tunnel surrounding rock stress is calculated based on D-P criterion and M-C criterion,respectively,and the influence degree of seepage effect on the two yield criteria is studied.The stress distribution characteristics of tunnel under two conditions of seepage effect are considered.Finally,a parameter analysis is made on the influencing factors of subsea tunnel surrounding rock plastic zone radius.Based on the influence law of seepage effect on the stress of subsea tunnel obtained in this paper,it can provide a theoretical reference for the design of tunnel support and parameter optimization with the plastic zone radius as objective function,in order to better guide the design and construction of deep-sea tunnels.