Research On The Stress-deformation Behavior Of Ultrahigh Inlaid Concrete Faced Rockfill Dam

With the development of hydropower in China, building 300m level ultrahigh concrete faced rockfill dam (CFRD) has become an inevitable trend. The deformation control of rockfill and the crack prevention of slab are the key problems of building ultrahigh CFRD. A lot of research results show that when the height of dam increased from 200m to 300m, the deformation of the dam almost doubled. The deformation of the dam will inevietably lead to different degrees of cracks in the slab, which can threaten the safety of the dam. Therefore,aiming at the optimization design of conventional face rockfill dam, it presents the design idea to build the ultrahigh inlaid CFRD which can make sense for the building of 300m level ultrahigh CFRD in engineering construction.In this paper, the finite element midpoint increment method is used to study the stress-deformation characteristics of inlaid CFRD. On the basis of this, the design scheme of the high modulus zone of inlaid CFRD is optimized. Based on the orthogonal test method, the sensitivity analysis of the Duncan-Change E-B model parameters in the high modulus zone is carried out. The main contents and main conclusions are as follows:(1) Aiming at key problems in the construction of 300m level ultrahigh CFRD, in this paper, by setting the dam heel concrete structure at the bottom of the upstream of the face dam and reducing the slab length which can improve the tensile state of slab. And to reduce the deformation of rockfill, a high modulus zone is set on the middle part of upstream position.Based on this, the design idea of the new dam type of inlaid CFRD is put forward further.(2) Under the action of dead weight. and water load, the construction process and impounding process of conventional CFRD, inlaid CFRD and inlaid CFRD with high modulus zone are simulated. The stress-deformation characteristics of the above three types of face rockfill dam are systematically studied. The results show that setting dam heel and high modulus zone both can improve the stress-deformation of dam body and slab. The effect of setting high modulus zone of inlaid CFRD is best for improving the stress-deformation of the dam and the slab, which lay the foundation for the following research.(3) In the design of ultrahigh inlaid concrete face rockfill dam, under the premise of improving the stress-deformation of the dam and the slab as far as possible,it makes an optimization research on the initial elevation and the height of high modulus zone by numerical calculation method. The results show that comparing with other schemes, it has obviously improving effect when the initial elevation of high modulus zone is 23% of the maximum dam height and the height is 38% of the maximum dam height.(4) Based on the orthogonal test method, the concrete faced rockfill dam with high modulus zone is taken as examples in this paper to conduct the sensitivity analysis on the high modulus zone of Duncan-Change E-B model parameters, and then make a contrastive analysis of range and variance on different orthogonal test schemes. The results show that the parameter of Kb has high sensitivity and remarkable impact on the dam settlement u3, the deflection of slab w and the along slope stress ?, and followed by ?, m. K,n, Rf and ?? which have lower sensitivity.The research results in this paper can provide reference and application on improving the stress state of slab and reducing the deformation of rockfill. And it also provides a way to confirm. the constitutive model parameters of rockfill which is more accurate, faster and realistic. It can offer strong supports to the safety of construction and long-term operation of 300m level ultrahigh CFRD projects.