| Southwest China is rich in water resources,and in order to ensure the national energy supply and optimize the water resources allocation,a large number of hydraulic tunnels have been built in this area.The geological environment,spatial structure form and interaction mechanism of hydraulic tunnel are all very complex.Meanwhile,Southwest China belongs to the high earthquake-prone area.Once a strong earthquake occurs,it will directly threaten the safety and stability of hydraulic tunnel.Therefore,studying the seismic response characteristics and failure mechanism of hydraulic tunnel under complex conditions,and proposing the seismic dynamic stability evaluation method for hydraulic tunnel structure are of great theoretical value and engineering practical significance to ensure the long-term safe and stable operation of hydraulic tunnel.In this paper,some key problems in seismic response for hydraulic tunnel and seismic safety evaluation of lining structure under complex conditions are studied in depth,including analysis method of dynamic combined action between surrounding rock and bolt for hydraulic tunnel,seismic response analysis method for deep-buried hydraulic tunnel across fault,seismic response analysis method for hydraulic tunnel portal section,analysis method of dynamic combined action between fluid and lining for hydraulic tunnel,and seismic performance assessment method for hydraulic tunnel structure.The main research contents are as follows:(1)The analysis method of dynamic combined action between surrounding rock and bolt for hydraulic tunnel is studied.The general mechanical response characteristics of rock materials under dynamic cyclic load are summarized,and the calculation formulas for the dynamic elastic modulus,dynamic tensile strength and compressive strength of rock are proposed.Considering the non-associated flow rule,a three-dimensional elastoplastic damaged dynamic constitutive model reflecting the dynamic response characteristics of rock is established by introducing damage coefficient,and the finite element implementation steps of the constitutive model are given.The support mechanism of fully grouted rock bolt based on the neutral point theory is studied,and the support effect of bolt on surrounding rock is discussed from two aspects: reinforcement of surrounding rock parameters and mechanical constraint of bolt.Based on the trilinear shear slip model,the differential equation of load transfer between bolt and surrounding rock is deduced,and the internal force distribution of bolt is obtained by solving the equation iteratively.Combined with the dynamic finite element method,a dynamic algorithm of bolt considering the shear damage-slip of anchoring interface is proposed.Then,the analysis method of dynamic combined action between surrounding rock and bolt for hydraulic tunnel is formed.(2)The seismic response analysis method for deep-buried hydraulic tunnel across fault is studied.Aiming at the problem that the finite element model is inconvenient to be built to the ground surface in dynamic time-history analysis of deep-buried hydraulic tunnel,an artificial boundary setting method considering the propagation characteristics of seismic wave field in underground infinite area is proposed.That is to say,all six directions of the model are artificially truncated: the viscoelastic artificial boundary is set at the top and bottom,the free field artificial boundary is set around,and the free wave field reflected from the ground surface to the top artificial boundary is calculated by the analytical method.Considering the influences of vibration wear factor and relative velocity factor on the seismic deterioration of contact surface,the dynamic variable shear strength parameters of contact surface are obtained.Aiming at the dynamic interaction characteristics between surrounding rock and fault under seismic load,based on the point-to-point contact type,a dynamic contact force algorithm is proposed which can reflect several contact states and take into account the cohesion and shear strength deterioration effect of contact surface by introducing the point-to-surface contact type.Then,the seismic response analysis method for deep-buried hydraulic tunnel across fault is formed.(3)The seismic response analysis method for hydraulic tunnel portal section is studied.Assuming that the seismic wave is vertical incident elastic plane wave,the input methods of plane P-wave and S-wave are studied.Based on the viscoelastic artificial boundary,the calculation formulas for the equivalent nodal force at each artificial boundary are deduced to realize the seismic wave input at portal section.Based on the basic theory of continuous damage mechanics,considering the damage effect on the initial stiffness of concrete material,the stress-strain constitutive relationship curves of concrete under uniaxial tension and compression are defined.The damage coefficient expressions under tension and compression are deduced,and the one-dimensional damage model is extended to three-dimensional state.A three-dimensional elastic dynamic damaged constitutive model of concrete lining is established.Aiming at the separation and slip phenomena in the combined seismic response between surrounding rock and lining for hydraulic tunnel,based on the dynamic contact force method,an analytical model of dynamic combined bearing between surrounding rock and lining is established,in which the dynamic contact force of contact node is calculated by the point-to-point contact type.Then,the seismic response analysis method for hydraulic tunnel portal section is formed.(4)The analysis method of dynamic combined action between fluid and lining for hydraulic tunnel is studied.Assuming that the water inside hydraulic tunnel is incompressible viscous flow,the ALE method is used to describe the movement and deformation process of fluid mesh,and the dynamic governing equations of incompressible viscous flow are studied.Combined with the boundary and initial conditions,the governing equations are discretized by the finite element method,and the Newton-Raphson iterative calculation scheme of the finite element equations is established.In the ALE finite element analysis,the calculation mesh is no longer fixed in space and needs to be updated continuously to avoid deformity.For this reason,the whole fluid region is regarded as an elastomer,and a fluid mesh updating method based on the pseudo-elastomer method is established.According to the fluid-lining dynamic coupling action characteristics,let the coupling boundary satisfy the equal velocity condition,a fluid-lining dynamic coupling iterative algorithm based on ALE is established with the coupling force as the convergence control index.Then,the analysis method of dynamic combined action between fluid and lining for hydraulic tunnel is formed.(5)The seismic performance assessment system for hydraulic tunnel structure based on probability analysis is studied.The IDA method is introduced into the seismic dynamic stability assessment field of hydraulic tunnel structure,and the seismic vulnerability analysis method based on IDA is studied.The selecting method of seismic records for IDA is discussed,and the damage coefficient of lining characteristic parts after earthquake is selected as the structural performance parameter.By determining the limit values of damage coefficient,the 5-level seismic damage classification standard and 4-level seismic performance level suitable for the seismic safety evaluation of tunnel structure are suggested.A seismic performance assessment method for hydraulic tunnel structure based on IDA is proposed.Based on the basic reliability theory,the structural reliability calculation method based on the response surface method and JC method is studied.Considering the seismic load as accidental load,the calculation formula for the seismic reliability of tunnel structure is deduced,and the estimation method for the earthquake occurrence probability in engineering area is explored.A seismic performance assessment method for hydraulic tunnel structure based on the reliability method is proposed.Then,the seismic performance assessment system for hydraulic tunnel structure based on probability analysis is formed. |
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