Study On Shear Safety Of Arch Dam Based On Nonlinear Trial-load Method

Arch dams are widely used in the dam construction industry because of their economy and safety.The number of arch dams in China is large and is still growing.Most of the arch dams that have been built have more or less cracks in the dam body,and cracks with different cracking degrees have different effects on the normal operation and safety of the dam.The occurrence and expansion of cracks are often regarded as a dangerous sign of dam failure.Therefore,the research on the damage of arch dam cracks and the safety of cracked arch dams has always attracted the attention of the engineering community.In the design of arch dams and structural safety assessment in China,we mainly focus on the study of the maximum principal tension and compressive stress,and there is a lack of research on the shear safety.However,there are various weak surfaces of arch dams,such as the dam's transverse joints,construction layers and cracking surfaces.These weak surfaces are either opened or closed,or formed into weak surfaces after repair.These weak surfaces have little effect on the compressive strength of the defect site,but have a greater effect on the shear(tensile/compressive shear)strength of the weak face,which may cause the overall safety of the arch dam with a higher level of shear stress to decrease.,Making the shear safety becomes a controlling factor for dam safety.For arch dams experiencing high shear stress or those with degraded shear cohesion even subjected to a low stress level,it is insufficient to evaluate the strength safety of the arch dam structure simply by tension/compression stress criteria.Developing criteria based on shear stress should be a significant supplement to safety evaluation methods of arch dam structures.In this paper,with the help of ADAO software,based on the calculation examples of seven arch dams,the shear safety analysis of arch dams is carried out.In order to solve the above problems,this paper,based on the calculation examples of seven arch dams,uses ADAO software to analysis and research on the shear safety of the arch dam body,and initially gives the recommended values of the shear strength safety factor control index.The main research contents are as follows:(1)The structural characteristics and development overview of arch dams are introduced,the main methods used in stress analysis of arch dams at home and abroad are summarized.Analyze the similarities and differences in structural safety control standards between China,the United States and Europe,and the resulting body shape differences.It paves the way for the advancement of shear safety control criteria for arch dams in China.(2)The method and calculation steps for the shear safety analysis and evaluation of arch dam structures based on the comprehensive strength reduction-overload method are introduced,as well as the analysis method of the overall stability of the arch dam and the basis for determining its instability.(3)Using ADAO software to simulate and analyze the whole process of non-linear failure of seven arch dams under the strength reduction and overload modes.The safety and differences of arch dam structures considering only the"tension/compression" failure mode and both the "tension/compression" and"tension-shear/compression-shear" failure modes are studied.The influence of the"tension-shear/compression-shear" failure mode on the safety has been identified for the arch dam structures.(4)The control value of the shear safety factor of the most unfavorable cross section of arch dam body based on linear elasticity analysis is studied.The control index value of the shear safety factor of arch dam body section is initially discussed through seven examples.