Working Performance Of Asphalt Concrete Impervious Core Wall Of Miaotang Reservoir Rockfill Dam And Its Influencing Factors

Asphalt concrete core wall dam is a rising type of dam,and it is necessary to study its overall safety and stability.The stress on the core wall structure of asphalt concrete dam is complex,which is related to the overall performance evaluation of the dam,and further research is needed.Based on the asphalt concrete core dam under construction of Miaotang Reservoir in Wushan County,Chongqing,this thesis studies the working performance of asphalt concrete core dam using a combination of laboratory test and numerical simulation.The research results can provide theoretical basis and beneficial references for the design and construction of similar projects.The main work and achievements of the thesis are as follows:(1)Based on the site rolling test,the mechanical properties of different rockfill materials are studied using laboratory test methods such as specific gravity test,relative density test,compression test,permeability test and triaxial test.The results show that the basic physical and mechanical parameters,the shear strength index and Duncan-Chang model parameters of the two rockfill materials are within a reasonable range.All tests have achieved the test purpose,providing certain reference for site rolling test and subsequent dam design and construction.(2)The working performance of asphalt concrete core dam in Miaotang Reservoir is studied by numerical simulation method.The results show that during the storage period,the maximum dam settlement occurs at about 2/3 of the dam height,which is 102.5 cm,not exceeding 1%of the maximum dam height.The stress of the core wall occurs at the bottom and is basically compressed.Only a small area of tensile stress appears at the dam abutment close to the bank slope with a maximum tensile stress of 100.78 k Pa,which does not exceed the ultimate tensile strength of asphalt concrete.The stress levels of the core wall under the two working conditions are 0.5118 and 0.441,both less than 0.77,and the core wall will not undergo shear failure.The stress and deformation results of the dam body and core wall conform to the general laws of similar projects,indicating that the dam design scheme is reasonable.(3)Based on the construction experience of similar projects and the current national design research scheme,the finite element method is used to conduct two-dimensional and three-dimensional calculation.The results show that the mechanical properties of the rockfill zone control the stress and deformation of the entire dam body,directly affecting the working performance of the asphalt concrete core wall.For stress and deformation of the core wall,the sensitivity of R_f,K,K_b andφare high in rockfill parameters,while K,K_b andφare mainly sensitive parameters in asphalt concrete parameters.The non rock-socketed slope angle and rock-socketed width of the base have a significant impact on the stress and deformation of the connection structure between the core wall and the base.The various indicators of stress and deformation in the proposed base shape optimization plan have decreased to varying degrees,especially the maximum tensile stress has decreased by 71.1%compared to the initial plan.The smaller the variable slope angle of the bank slope,the more symmetrical the valley terrain and the lower the height of the variable slope point,the better the stress condition of the core wall,which is more conducive to the deformation control of the core wall.The stress analysis results of the core wall also verify this conclusion.