Reasearch On Equivalent Strength Of Induced Joints In RCC Arch Dam With Experimental Study And Numerical Calculation

After years of practice,it has been proved that the split joint of dam is one of the effective temperature control measures for arch dams,and plays a very important role in controlling the deve.lopment of dam stress.For the RCC dam,when the temperature of the dam body drops drastically,there will be a large temperature stress which will cause the dam to crack.In order to prevent the occurrence of cracks,the dam builders often use induced joint to artificially weaken the tensile strength of the dam.When the tensile stress of the dam is large,it can guide the crack to crack in the section of the induced joint in order to protect the dam.However,cracks still appear in some RCC arch dams that have been equipped with induced joint at home and abroad,and the induced joint has not played the desired role.Therefore,master the surface state of the induced joint,equivalent strength and arrangement law have great practical significance to prevent the disorderly cracking of the dam.In this paper,the equivalent strength and arrangement law of RCC with Bidirectional spacer induced joint are studied.Five factors such as weakening degree,number of induced plates,induced plates spacing,age and strength are considered in the design of the test scheme.Carried out the axial tension test,and obtained the variation law of equivalent strength of induced seam under various influencing factors:1)The equivalent strength of RCC induced joint decreases with the increase of weakening degree;2)With the increase of the number of induction plates,the equivalent strength of the induced joint decreases gradually,and the two are logarithmically correlated;3)The equivalent strength of RCC induced joint increases with the increase of the induced plates spacing,but the increase range decreases gradually;4)The equivalent strength of RCC induced joint increases rapidly in the early stage,and its variation with age is almost the same as the increase law of tensile strength of concrete body.However,there are differences in the degree of strength weakening at each age;5)The equivalent strength of induced joint increases with the increase of tensile strength of concrete body.The weakening degree of induced joint to section strength decreases with the increase of concrete strength.In view of the above laws,the following Suggestions can be provided the arrangement of induced joint for actual arch dam:Appropriately increase the weakening degree of the induced joint of arch dam can reduce the equivalent strength of the induced joint.And make the section of the induced joint crack faster in order to protect the dam.However,the number of induction plates can be properly increased or the spacing of induction plates can be reduced when the weakening degree of induced joint should not be set too large.It not only does not affect the stress transfer of the induced joint section,but also can weaken the dam section strength the section strength of the dam.Used finite element software to establish a model of RCC induced joint specimen.Axial load was applied to it according to the loading mode of the test.Obtained The stress cloud diagram of the section where the induced joint is located,and understood its stress distribution state.More clearly grasped the fracture process of induced joint specimen,that is,The fracture of RCC induced joint specimen started from the four edges of the induced plate,and gradually extended outward to the edge of the specimen,finally the brittle fracture occurred.The rationality of the numerical simulation parameters and the correctness of the test results and laws was verified by Comparative between the equivalent strength of the test and the equivalent strength of the simulation.By exploring the correlation between equivalent strength and fracture toughness,derived the fracture toughness and its laws under different degree of weakening and different strength of concrete:1)The fracture toughness and toughness ratio of induced joint decrease with the increase of weakening degree.2)The fracture toughness of concrete increases with the increase of strength grade,and the two are linearly related.The improvement of RCC strength grade has a significant effect on the bearing capacity of specimen,which also means that the greater the fracture energy required when the specimen is destroyed.Finally,combined the test results with the actual project.According to the fracture toughness obtained,calculated the equivalent strength of Daoliu river RCC arch dam with different reserved joints,and obtained the arrangement law of reserved joints,that is,the equivalent strength of the dam decreases with the increase of the weakening degree,decreases with the decrease vertical arrangement size of the reserved joint,and it is consistent with the test law of RCC induced joint.It can provide a reference for the arrangement of induced joints of the Daoliu river RCC arch dam.