Feedback analysis on temperature field and stress simulation of Xiaowan arch dam in the operation period
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Abstract:
The arch dam is a three-dimensional shell structure with a complex operating environment and complicated stress state,its actual working behavior is different from the design condition.During the operation of a high arch dam,the temperature load,which is determined by the difference between the temperature field during operation and its joint closure temperature field,is one of the main loads.Generally speaking,it is easy to obtain the temperature field of arch sealing.However,thermal analysis of the arch dam during operation is difficult due to the influence of climate conditions,structural form,and operation modes.In addition,as the main waterholding structure,the stress state of the arch dam during operation is sophisticated.The mechanical parameters of concrete may differ from the experimental values.Therefore,the research on the real working behavior of the Xiaowan arch dam is of great significance. The material parameters of the Xiaowan arch dam were investigated and the stress distribution was simulated by the finite element method.The temperature distribution on the dam surfaces was fitted by the polynomial as the thermal boundary condition based on the measured temperature.Then transient temperature field of the Xiaowan arch dam was calculated step by step.The elastic modulus of dam concrete and foundation rocks were continuously adjusted to minimize the differentials between the numerical displacements calculated by FEM and the actual displacement measured by the plumb lines.The elastic modulus with the smallest displacement errors was viewed as the actual material parameters.The simulation of stress distribution of the Xiaowan arch dam was carried out based on the inversion results of the temperature field and material parameters. Conclusions (1)The feedback temperature field could represent the temperature field distribution of the Xiaowan arch dam during the operation period.The temperature of the upstream dam surface was mainly affected by the reservoir water.Besides,the temperature of the upstream dam surface near the foundation was higher,between 17 ℃ and 19 ℃ due to the influence of the ground temperature and slag in front of the dam.The temperature of the downstream dam surface was mainly affected by atmospheric temperature,showing a phenomenon that the temperature was higher on both sides than in the middle section.(2) The elastic modulus of the dam concrete during the operation was increased by about 30% relative to the test value.Besides,the deformation modulus of the bedrock was 20%~45% higher than the test value.(3) The calculated displacement agreed well with the measured data with the same trend.The displacement of the Xiaowan arch dam was closely related to the upstream water level.The dam had a trend of slow deformation to the downstream because the aging effect had not yet fully converged at present.(4) The upstream dam surface was basically in a pressure state.Besides,the maximum compressive stress,which was located at the height of 975 m,was about 10 MPa.However,the dam surface above the water level was under tension in winter,and the maximum tensile stress was about 0.6 MPa.The downstream dam surface was basically in a compressive state,and the maximum compressive stress could reach to 17.3 MPa,which was located at the dam toe.Besides,the te2nsile stress zone appeared near the interface between the dam body and the foundation due to the stress concentration,and the global maximum tensile stress was about 0.8 MPa,although the operating state of the dam was still in the safe scope. Conclusions（1）The temperature of the downstream dam surface was mainly affected by atmospheric temperature,showing a phenomenon that the temperature was higher on both sides than the middle section.（2） The elastic modulus of the dam concrete during the operation was increased by about 30% relative to the test value.（3）The stress distributions of the Xiaowan arch dam revealed that its operating state was still in the safe scope.
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