Research On Back Analysis Of Temperature Field Of RCC Gravity Dam Based On Genetic Algorithm

RCC will produce temperature cracks due to hydration heat reaction of concrete or ambient temperature change,and the generation of cracks will lead to the reduction of dam strength,and then greatly affect the safety of dam.In order to ensure the strength and safe service life of the dam,it is necessary to predict and protect the crack,and take reasonable and effective temperature control measures during construction and operation.The temperature and stress sim ulation calculation of the project can effectively predict the temperature and stress changes of the dam body,so as to effectively predict and prevent the possible cracks in time.The material thermodynamic parameters required for simulation calculation are generally selected based on experiment or engineering experience,and the experimental environment conditions in the laboratory are quite different from the construction environment,so the obtained result parameters are different from the actual ones.Therefore,the temperature field of the dam body can be analyzed by inversion to obtain more reliable thermal parameters.When solving the temperature field back analysis,the accuracy of the back analysis result is affected by the quality of the calculation method,the integrity of the engineering data and whether the simulation process is consistent with the actual construction.In this paper,on the basis of the results of the temperature field back analysis,taking a RCC dam as an example,the genetic algorithm is used to study the temperature field back analysis.Considering the directness of calculation and the main research focus,this paper mainly takes the thermal conductivityj the final adiabatic temperature rise and its temperature rise constant as the research object,analyzes and compares the reliability and accuracy of the parameters of the inversion results under the circumstances of different number of parameters and different number of measurement points.The main research results of this paper are as follows.(1)The back analysis model of temperature field is established.Based on the basic theory and method of inversion analysis,according to the calculation principle of RCC dam temperature field,combining the numerical calculation model of temperature field with the back analysis theory,taking the sum of squares of the difference between measured and calculated temperature values as the objective function,the constraint conditions and control parameter methods in the iterative process are determined,and the back analysis model of temperature field is established.The calculation procedure of temperature field back analysis of RCC dam based on genetic algorithm is given.(2)The measured temperature of the measured point of the dam is analyzed,and the ANSYS finite element model is established according to the engineering data.Using ANSYS thermal analysis part to calculate the temperature field of RCC dam,combined with the actual construction conditions and steps,using ANSYS finite element software to simulate the actual construction process of the dam,the temperature field simulation model of a RCC dam 35#section(non-overflow dam section)is established.The temperature monitoring data of typical measuring points in 35#dam section are analyzed.(3)The inversion analysis program is written based on genetic algorithm,the inversion analysis program was compiled.Firstly,the precision of inversion results of thermal parameters of temperature field was analyzed with the number of parameters as the variable.Using MATLAB software to write genetic algorithm code program,and using MATLAB to call ANSYS finite element software for temperature field inversion calculation.Based on the measured temperature data of T3-23 and T3-24,the thermal conductivity of RCC in Ⅱ-2 area of 35#dam section,the final adiabatic temperature rise and its constant are taken as the research objects,and the number of simultaneous inversion parameters is taken as the variable.The inversion analysis of single parameter,two parameter and three parameter is carried out respectively.The parameter results obtained by inversion are substituted into the forward analysis calculation of temperature field,and the calculated temperature values of measuring points are compared with the measured temperature values.The results show that the calculated temperature values obtained from the four inversion cases are in good agreement with the measured temperature trend,and the diachronic curve is in good agreement.The comparison shows that the inversion of the three parameters at the same time is better.It also shows that the results of inversion analysis of RCC temperature field by genetic algorithm are more reliable and accurate,which can provide guidance and theoretical basis for practical engineering,and provide certain theoretical support for temperature control direction of subsequent construction.(4)When the number of measuring points based on analysis is different,the difference and influence of thermal parameter values obtained from inversion on the accuracy of temperature field results.With the number of measuring points as the variable,considering three measuring points,six measuring points and nine measuring points,the influence of thermal conductivity,final adiabatic temperature rise and constant on the accuracy of the results is inverted simultaneously.By comparing the calculated value of temperature with the measured value,it can be seen that the diachronic variation curves of the calculated value of temperature at the measured point and the measured value are in good agreement under three different conditions.Moreover,from the overall degree of agreement of the measured points,the coincidence degree of the measured points under nine measured conditions is higher,indicating that the inversion results are more accurate,and the obtained thermal parameter values are closer to the real values of the material.It also shows that under the condition of accurate and sufficient measurement point data,the results obtained by using genetic algorithm inversion analysis of RCC temperature field are more reliable and accurate,and through analyzing the temperature field results obtained by feedback calculation,the distribution and variation of temperature field of dam body are obtained,so as to propose more economical and reasonable temperature control measures for engineering.To provide certain guidance for the subsequent construction.