Monolithic Stability Of Arch Dam Subject To Penetrated Damage:A Pilot Study

With the rapid progress in the construction activities of supper high dams(H=200～300m)in China and the continuous boost of river basin planning,the reservoirdam system has become an important link to ensure economic and social stability as well as the safety of people’s lives and property.Consequently,the safety of these dams against potential terrorist attack has become increasingly noticeable.Under such circumstances,the “National Natural Science Foundation of China”(NSFC)approved the Key Project(No.51939008)in 2019 that is intended to establish emergency plan under wartime or terrorist attack,and to guarantee the safety of large hydraulic projects.This thesis presents a part of the research supported by the NSFC under grant number 51939008.Focused on the national demand of safety calibration of high arch dam subject to penetrated damage,the major advances are achieved as follows:(1)According to the basic principle of the trial load method,the structure analysis algorithm for the arch dam is implemented in the software ANSYS,by which the simulation of the penetrated damage holes at any position of the dam body is realized.The algorithm and program possess remarkable advantages of simplicity and facilitation,standardization,free adjustment of arch-cantilever density,and automatic computation in the whole process of “modeling-loading-solving-data digging”.(2)According to the principle of lower-bound limit analysis,the lower-bound limit analysis method for arch-cantilever element is further proposed,and the corresponding calculation program is implemented.To simplify the optimization solution procedure,the arch rings and cantilevers are firstly discretized in segments with regard to conjugate nodes,then bending moments and axial forces are employed as independent variables.The nonlinear programming is employed to fast handle the nonlinearity of the yield function.(3)The safety evaluation methods and indices which are world widely used in the community of arch dam engineering are summarized.According to the existing domestic design codes and typical engineering case data,the local and overall control indices with respect to stress and monolithic overloading capacity,are used to construct an early warning system of three-levels.(4)For the XBL project,the proposed safety evaluation system of arch dam subject to penetrated damage is exercised.The stress,displacement and the lower bound safety factor under three work situations: intact dam,central penetrated hole through crown cantilever,and side penetrated hole near abutment,are calculated,respectively.The safety degree is given and corresponding early warning level is set.The roadmap elaborated in this thesis is constructed by major components in a flowchart of “software platform of trial load method-limit analysis-safety evaluation-early warning alarm”.It is actually an important pilot study that possesses high potentiality to be extended by other advanced computational methods(e.g.FEM,MMs,SPH,etc.).In addition,it is already able to cope with practice issues rather well.