Experimental On Equivalent Strength Of Induced Joint And Jointing Design Of RCC Arch Dam

Roller compacted concrete(RCC)arch dam adopts the construction method of thin layer pouring without longitudinal and continuous rise in large area,which results in most hydration heat produced by concrete accumulates in the dam within a short period and cannot dissipate in time,thus forming the temperature difference between inside and outside,as well as layers of the dam.It is easier for dam to produce temperature cracks under the restraint of the surrounding foundation when the temperature drop.As a structural anti-cracking measure of the RCC arch dam,whether the induced joints can crack firstly to release temperature stress and control the disordered crack when the dam temperature drops,mainly depends on the equivalent strength,structure form and setting position.However,the theoretical and experimental studies on fracture mechanism of induced joints are so little that it can't meet the great need of practical application.The researches on the shape of induced joints,its location,the size of embedded cracks,as well as the center-to-center distance of two adjacent cracks etc.,haven't come to the same conclusion until now.So,this paper relies on the project of National Natural Science Foundation of China "Experimental study and Real-time Simulation of Induced Joint of RCC Arch Dam Considering Multi-factors",based on the equivalent strength test of RCC induced joint and the simulation analysis of temperature stress of Tuxikou RCC arch dam,the induced joint arrangement,structural design and cracking prediction of the dam body are carried out.In this paper,the non-penetrating RCC induced joint specimen is used to simulate the bidirectional interval induced joint in practical engineering.The functional relationship between the equivalent strength of the non-penetrating rectangular induced joint and the non-penetrating elliptical induced joint with the weakening degree and the concrete age are established by axial tension test.On this basis,the equivalent strength error of simplifyingrectangular induced joint to the same size elliptical induced joint of has been analyzed.The results show that the equivalent strength error between non-penetrating elliptic joint and the non-penetrating rectangular induced joint is less than 8%under the same induced joint size,concrete age and test conditions,and the error decreases gradually with the increase of the weakening degree,which verifies the reliability of elliptical simplified model in numerical calculation of temperature field cracking of the induced joints of actual RCC arch dam.In addition,the finite element analysis software ANSYS was used to simulate the temperature stress of Tuxikou RCC arch dam without induced joint.According to the distribution rule of stress field,the principle of induced joint arrangement and the joint separation practice of RCC arch dam have been built in China,the induced joint distribution and structural design of the dam body are carried out.Then the equivalent strength model of non-penetrating rectangular induced joints established in this paper was used to calculate the equivalent strength of the induced joint of the dam body,and it is applied as the calculation parameter of the joints element to the simulation and analysis program of temperature control of dam body compiled by the research group.After that the temperature stress simulation of the whole process from construction to operation was carried out by three-dimensional finite element method.Based on the simulation results,prediction of induced joint cracking and analysis of the influence of induced joint on dam body stress were carried out.The result shows that under the double temperature control measures of controlling pouring temperature and adopting water cooling in the whole dam,the temperature stress can be effectively released by setting bidirectional interval induced joints with equivalent strength less than 1.409MPa in the high tensile stress area of the dam body and ensure the safety of the dam body under temperature load.This study can provide theoretical basis and technical support for the design of induced joint of RCC arch dam,and can also provide reference for temperature control,crack prediction and prevention of the RCC arch dam.