Damage Evolution Analysis And Seismic Measures Of High Concrete Faced Rockfill Dam

Hydropower is an important part of building clean,low-carbon and sustainable energy system in China.High dam construction is an important foundation for hydropower development.Concrete face rockfill dam has become an important dam type for high dam construction because of its low cost,strong adaptability to complex terrain and good comprehensive seismic performance.In recent years,a large number of high faced rockfill dams have been planned and constructed in the western region of China,such as Houziyan(223.5 m),Lawa(239 m),Cihaxia(254 m)and Gushui(305 m),which marks the construction of faced rockfill dams in China is moving towards 300 m super high dams.However,frequent earthquakes and high intensity in the dam site always threaten the safe operation of high dams.In the event of an accident,it will not only bring a heavy blow to regional economic development,but also cause immeasurable secondary disasters downstream.Therefore,it is very important to carry out the seismic research of high dams and accurately grasp the structural safety state.Concrete face slab is the key component of anti-seepage system of high faced rockfill dam,and its safety and integrity are important defense lines to ensure the smooth operation of the dam.However,in the dam system,the size of the impervious panel is very small,which is thousands of times different from the overall scale of the dam.Therefore,there is still a big challenge between the fine simulation panel and the efficient analysis of the overall response of the dam in the conventional finite element analysis.Therefore,the current three-dimensional analysis of dams is mainly based on simplified sparse grids,which is difficult to accurately capture the dynamic response characteristics of impervious panels.On the other hand,concrete is quasi-brittle material.At present,the commonly used elastic model is difficult to describe the failure characteristics such as material stiffness degradation and stress release in the failure process,which is not convenient to reasonably and truly evaluate the seismic performance of the panel.In view of some limitations of the conventional method,This paper is based on the National Natural Science Foundation of China Youth Project(52009018)and China Postdoctoral Science Foundation Project(2020M670752).This paper first introduces and adopts the cross-scale modeling scheme of block discretization-interface grid reconstruction.Then,the static and dynamic response analysis of high face rockfill dam is carried out by using the polyhedral proportional boundary finite element method-finite element method coupling analysis strategy,combined with the concrete plastic damage model,the generalized elasticplastic model of rockfill material and the generalized plastic model of contact surface,and the influence of some key factors is discussed.The specific research contents and conclusions are summarized as follows :(1)Firstly,this paper introduces the calculation method and material constitutive theory,including the basic idea of SBFEM,concrete plastic damage model and the basic theory of generalized plastic model of rockfill.It provides technical support for subsequent work.(2)Referring to《Code for design of concrete faced rockfill dam》and related engineering design data,the geometric design parameters of dam type are selected.A three-dimensional refined analysis model of concrete faced dam is established by using the cross-scale modeling scheme of block discrete-interface mesh reconstruction,and the static and dynamic response analysis of the dam is carried out combined with the elastic-plastic material constitutive.The distribution of the stress of the concrete face slab with different numerical materials is compared.The spatial distribution of panel damage under earthquake is given.(3)The influence of the discrete grid size of the panel on the damage law is studied,and the optional value of the discrete grid size of the impervious panel is proposed when the fine analysis of the dam is carried out.The influence of some key factors such as different dam height,river bank slope panel width and water storage level before the dam on the damage degree of the panel is discussed.(4)Based on two engineering examples of Lawa and Houziyan,the damage law of seepage control panel under strong earthquake is discussed.According to the damage distribution,the improvement effects of different seismic strengthening measures were discussed,including the use of steel fiber reinforced concrete and the addition of horizontal joints.