Seepage-stress-damage Coupling Analysis Of Gravity Dam Based On Parameter Heterogeneity

Rock mass of dam foundation and concrete of dam body are prone to damage and failure under the action of high water storage head for concrete gravity dam.There are dynamic and mutual influences among stress,seepage and damage.So it is very important to study the damage behavior of gravity dam under the coupling of seepage,stress and damage.However,the existing researches in relation to the damage analysis of gravity dams based on the coupling effect of seepage-stress-damage are mainly aimed at the dam body.Lack of the relevant researches that the coupling effect of seepage-stress-damage is used to analyze the damage of dam foundation and the whole gravity dam.The effects of the cumulative process,the irreducible property of the damage and the heterogeneity of the dam body material are not taken into account in the existing researches.In addition,there is a lack of the basic of selecting parameters when the equivalent random mechanics is used to characterize the heterogeneity.In view of the above problems,this paper puts forward the coupling model of seepage-stress-damage and realization method for non-homogeneous gravity dam,and the following results are mainly obtained through in-depth study:(1)In view of the present dam body of gravity dam seepage-stress-damage coupling researches,the materials of the dam bodies are assumed the homogeneous condition.The mathematical model of seepage-stress-damage coupling is put forward for non-homogeneous gravity dams(including dam foundation and dam body).The current seepage-stress-damage coupling research of gravity dams is mainly focused on the analysis of the damage evolution of homogeneous dam body,and there is lacking of the seepage-stress-damage coupling study for the dam foundation.For this purpose,the seepage-stress coupling mathematical model is established when the concrete and rock is as porous media.Secondly,based on damage evolution model and damage-seepage coupling mathematical model of rock mass,a coupled seepage-stress-damage mathematical model for dam foundation considering the heterogeneity of materials is proposed.Meanwhile,based on damage evolution model and damage-seepage coupling mathematical model of concrete,a coupled seepage-stress-damage mathematical model for dam body considering the heterogeneity of materials is proposed.Finally,the seepage-stress-damage coupled partial differential equations of concrete and rock mass are compiled and embedded in the finite element program COMSOL,which provides theoretical and technical support for the study of the damage evolution of gravity dams under the coupling of seepage-stress-damage by numerical analysis.(2)In view of the current seepage-stress-damage coupling research in gravity dam,the cumulative effect of the water storage process on the damage and the irreducible property of the damage are not taken into account.So the dynamic damage evolution analysis method of gravity dams is proposed.In view of the existing damage and failure research on the seepage-stress-damage coupling for gravity dam,the boundary conditions of are usually set as stress boundary and seepage boundary related to the water head of different water level.So the cumulative process of damage can not be considered.Moreover,the stress and strain state of different storage head are different,which results in the loss or decrease of damage zone under the head of low storage water.Firstly,the damage is set as dependent variable,and the damage is assumed to increase or remain unchanged as the head of the storage head rises.Secondly,the stress boundary and seepage boundary in the numerical analysis program are set as dynamic increasing head boundaries in calculating the cumulative process of damage.(3)In response to the current study on the seepage stress damage coupling of concrete dam concrete,the concrete is usually considered as homogeneous material,and all of the damage research situation under the water head that is not higher than the normal water head.The theory and method of seepage-stress-damage coupling study for heterogeneous dams under the action of overloaded water storage head are put forward.The current seepage-stress-damage coupling studies for gravity dams are based on the homogeneous condition of the dam materials,which do not consider the important characteristics of the heterogeneity of the concrete material due to the uncertainty of the aggregate particles and the uncertainty of the pore distribution.The damage zone and the damage coefficient are obtained under the water head beneath the normal water storage position.The effect of overloading water storage head on dam damage is not considered.So The evolution law of dam body damage and the safety reserve function of dam body can not be obtained under overload.For this reason,firstly,the stress and seepage boundary are set as the dynamic rising head.The dynamic damage and failure law of dam body under the coupling of seepage and stress damage is studied when the material is homogeneous.Secondly,the Morris global sensitivity method is written by MATLAB program.The sensitivity order of dam deformation and damage influenced by physical parameters of concrete is analyzed.It provides theoretical reference for selecting mechanical parameters to characterize the heterogeneity of concrete.Thirdly,based on COMSOL program and MATLAB program co simulation,the modeling of dam concrete material heterogeneity is realized.The damage and crack evolution law of the dam body under the coupling of seepage-stress-damage is studied when the material is heterogeneous.Furthermore,the evolution process of the elastic modulus reduction and the evolution process of concrete permeability coefficient are also analyzed when the material of dam body is heterogeneous.Finally,in order to explore the effect of material homogeneity on damage evolution law,the damage distribution law of dam body with different shape parameter m is compared and analyzed.(4)In view of the present progressive failure simulation study of dam foundation under seepage-stress coupling for gravity dams,the deficiencies is that the brittle failure behavior and process which can not be reflected by the constitutive model of rock mass.As for the study of damage evolution for gravity dam foundation,there is a lack of considering the cumulative impact of the increase of head of water storage.The theory and method of seepage-stress-damage coupling study for heterogeneous foundation under the action of overloaded water storage head are put forward.At present,in the simulation study of progressive failure of gravity dam foundation under seepage-stress coupling,Mohr-Coulomb elastoplastic and Druck-Prager elastoplastic constitutive models are often used in rock mass constitutive models.However,the brittle failure behavior and process of rock mass can not reflected by these constitutive models.Therefore,it is impossible to describe the effect of damage on the stiffness and permeability of rock mass for dam foundation.At the same time,based on the damage theory,the damage and failure of rock mass of the dam foundation under the coupled seepage stress damage field are studied.In view of the damage evolution research of dam foundation,the cumulative influence process of damage by water head increasing is not considered.In order to make up for the above shortcomings,the following work has been carried out: Firstly,the damage evolution model and seepage damage coupling model of rock mass are studied,and a coupled mathematical model for seepage-stress-damage field of heterogeneous dam foundation is proposed.Secondly,based on the multi field coupling model of heterogeneous rock mass,the damage evolution behavior of rock mass in the heterogeneous dam foundation is studied,and the differences and similarities of damage are compared when the rock mass material is homogeneous and heterogeneous.Thirdly,the Druck-Prager based constitutive model is used to study the evolution process of the plastic zone of the dam foundation rock.At the same time,the strength reduction method and the overload safety coefficient method are used to analyze the stability of the dam foundation.In addition,Morris global sensitivity analysis program is written by MATLAB.Combined with the strength reduction factor method,the influence of main weak rock layers on the stability of the dam is studied.The theoretical reference can be provided for the selection of the reinforcement scheme of the dam foundation.Finally,the similarities and differences between the plastic penetrated zone and the damage penetration area of the dam foundation under the two constitutive models are compared.(5)In view of the researches on numerical analysis of rock mass with cracks,there is a lack of research on finite element numerical analysis of dam foundation models with real cracks.Moreover,the influence of interlaced weak rock layer and fissures on damage evolution of dam foundation is not considered in the study of seepage stress damage field coupling.Therefore,the application of seepage stress damage coupling model to the whole non-uniform gravity dam structure is put forward.At present,the finite element numerical analysis program is used to consider fracture body at dam foundation.The influence of fractures body is indirectly studied by equivalent model.The numerical calculation model can not be established according to the true fracture distribution law.Moreover,the dam foundation model of the above seepage-stress-damage field analysis is relatively simple.The influence of interlaced weak rock and fissures on damage evolution of dam foundation is not considered.A concrete gravity dam project in Southwest China is taken as an example in the paper.Based on the hybrid data structure of NURBS-B-Rep-TEN and the measured data of fracture distribution,a 3D dam foundation geological model with random disk fracture body is established.The geological model is transformed into a finite element model after transformation.On a longitudinal section,the damage evolution law of gravity dam(dam body and dam foundation)under the coupling of seepage-stress-damage is analyzed and studied by considering material(concrete of dam body and rock of dam foundation)as non homogeneous.The results show: The dam foundation with interconnected fault is prone to damage area and damage area,and the safety reserve performance of dam body and dam foundation is relatively low.The initial location of damage and failure pattern of different dam sections are different for the two kinds of dam sections.