Prediction Of Mechanical Properties Of Dam Concrete Based On Maturity Method

The real strength and fracture performance of dam concrete is one of the prerequisites to ensure the accuracy of dam cracking risk analysis and safety assessment.This article aims to obtain the real mechanical properties of dam concrete.First,based on the strength and fracture performance test results of the full-graded and wet-screened concrete poured at the construction site,the maturity analysis of the mechanical properties of the dam concrete under the real service environment is carried out,the theoretical calculation formula and the functional relationship between mechanical properties and maturity index of dam concrete are defined,and the conversion relationship between mechanical properties of full graded and wet screened concrete is determined.At the same time,relying on the indoor large temperature and humidity environment box,the strength and fracture performance tests of wet screened concrete under different curing temperatures are carried out,the quantitative data of the influence of curing temperature on the strength and fracture performance of dam concrete are obtained,the prediction model of the real mechanical properties of dam wet screened concrete is established Finally,combining the obtained conversion relationship between the mechanical properties of the full-graded and wet-screened concrete,a model that can be used to predict the mechanical properties of the dam's full-graded concrete under the real environmental conditions on site is established.It has been verified that the prediction model can meet the needs of actual dam projects.The main research content and research results of this article are as follows:(1)Based on the real mechanical properties test results of full graded and wet sieved concrete poured in the dam construction site in spring,summer,autumn and winter,the strength and fracture properties of concrete poured in different seasons are compared.The influence of curing environment temperature and age on mechanical parameters of concrete is analyzed by using maturity theory,and the reliable conversion relationship of mechanical parameters of full graded and wet sieved concrete is clarified.The results show that due to the different curing temperature history,there are certain seasonal differences in the development of dam concrete strength and fracture performance;it is feasible to study the development law of dam concrete mechanical parameters through maturity theory;The conversion relationship of compressive strength and split tensile strength between full-graded and wet-screened concrete can be respectively taken as 0.88 and 0.74,The conversion relationship of initiation toughness,instability toughness and fracture energy between full-graded and wet-screened concrete can be respectively taken as 1.32,1.36 and 1.7.It has been verified that the above conversion relationship can more accurately convert the mechanical parameters of wet-screened concrete to the mechanical parameters of fully-graded concrete.(2)By carrying out three different curing temperature conditions for dam wet-screened concrete mechanical performance tests,each curing temperature was designed with 6 ages,and the effect of curing temperature and age on the mechanical properties of wet-screened concrete was systematically studied.The results show that the strength parameters and fracture parameters of wet-screened concrete increase with the increase of age under different curing temperature conditions;In the curing temperature range of 10? ?40?,the strength parameters and fracture parameters of wet-screened concrete is increase with the curing temperature.The temperature rises gradually;the environmental temperature suitable for the growth of the mechanical parameters of the wet-screened concrete of the dam is 40?.(3)Using the test results of the mechanical properties of dam wet-screened concrete with different curing temperatures,based on the maturity theory and the conversion relationship between the dam full-graded and wet-screened concrete mechanical parameters,the mechanical parameters model of the fully-graded concrete that can predict any temperature history are established.The prediction model was verified by the results of the dam concrete mechanical performance test on site,and the concepts of average absolute percentage error and weighted average absolute percentage error were selected to evaluate its accuracy.Furthermore,the prediction model is applied to actual engineering,and the prediction value is compared with the material parameter value of the traditional method.The results show that the average absolute percentage error and weighted average absolute percentage error of the predicted value of mechanical parameters and test values are both within 15%,indicating that the prediction accuracy of the prediction model built in this paper can meet the requirements of engineering use;The real mechanical parameters of dam concrete poured in different seasons Obviously different from the traditional method.When carrying out the dam structure simulation analysis,the prediction model is used to calculate the true strength and fracture parameters of the dam concrete,which is more accurate than that of the standard test under the condition of standard curing or concrete placement.