Finite Element Simulation Analysis And Safety Evaluation Of Muguaxi Arch Dam During Construction And Operation

Concrete arch dam is a kind of super statically indeterminate space structure with complex shape.Compared with gravity dam,it can bear large pressure with relatively small volume and make full use of the strong compressive strength of concrete.In addition,the dam can adjust itself when cracks occur due to external load,and it also has good seismic capacity.The influence of cracks is affected by many factors,including the chemical reactions produced by the formation process of concrete,the type of the basic materials,the concrete pouring climate and other external factors.Therefore,cracks have become an important problem puzzling concrete dams.During construction and before storage,several vertical and horizontal cracks were found on the upstream and downstream surfaces of the arch dam.The stability of cracks and its influence on the safety of arch dams during operation is one of the most important problems in engineering.Based on the design data of an arch dam structure,the relevant records during construction process and storage process,the temperature control measures,and the statistics of dam cracking.The thermal field and thermal stress in the process of dam construction and storage are simulated by ANSYS software,the crack stability and the treatment measures as well as the safety of arch dam are analyzed.The main conclusions are as follows:(1)The temperature variation law of dam body is consistent with other arch dams,and the calculated results are consistent with the measured values.Before water storage,the temperature is high at the elevation part of the middle and low part of the dam body,and the temperature of the high elevation part is low.Because of the small thickness of high range dam body,the water level is controlled by water temperature,the downstream surface changes with temperature and the gradient is large.After water storage,the upstream surface of arch dam is mainly affected by water temperature,which is consistent with the change law of reservoir water temperature.The downstream dam surface temperature is sensitive to the external temperature,and the temperature gradient is large.After one year of operation,the internal temperature of dam body tends to be uniform and stable.(2)When the water level reaches the normal level,the dam body shows signs of deformation,and it is distributed symmetrically on both sides of the dam.The maximum deformation along the river is near the middle of the arch crown.The first principal stress at the dam heel of the riverbed dam is tensile stress,and the first principal stress at the middle and low elevation dam section is tensile stress,there is a local stress concentrationphenomenon,except for this area,its value is basically within 1.5MPa,and the tensile stress zone extends downstream about 2?3 m.The third principal stress at the toe of the dam is mainly compressive,the maximum is about 11.0 MPa;and the straight and horizontal cracks are mutually extruded.During the service period of the arch dam,the temperature drop has obvious influence on the stress and strain of the arch dam.The stress on the crack joint surface is basically compressed,and the maximum compressive stress is about 0.3MPa.The crack is stable during the service period.(3)The results of overload calculation show that: when the overload coefficient is less than 2.0,the dam body is basically in the elastic working state,and the obvious plastic deformation begins after the overload coefficient is greater than 2.0,and the overall overload coefficient of the dam is above 3.5.(4)The results show that during the construction process the cracks in the dam body significantly reduce the safety of the arch dam.After taking the crack treatment measures,the safety of the dam body is less different from that of the dam body without cracking.Therefore,after the treatment of the cracks,the working behavior of the dam can reach the state before the crack.The above results provide a reference for the feasibility demonstration of water storage in the lower sluice of the arch dam.At the same time,it also provides reference for similar projects.