Stability Analysis And Section Division Optimization Of High CFRD

Concrete Faced Rockfill Dam (CFRD) was widely adopted in the recent decades because of its good security, extensive adaptability, convenient construction, small investment, short construction period. With the development of techniques and continuous application of new technologies about CFRD, it is becoming a competitive dam type among earth and rockfill dams and the height of CFRD is increasing. Shui Buya CFRD (dam height 233m) is the highest one among all the established CFRD in the world, and 300m level-CFRD is designed at home and abroad.The increase of dam height raises a more strict claim about the security for the design of CFRD. The research approach adequate for 100m level-CFRD needed to be revaluated while the engineering characteristics and other key technologies of 300m level-CFRD are also requiring deep analysis, among which the slope stability and section division optimization are the critical technical issues. For a long time, the CFRD was considered it has a good stability due to the rockfill's erosion-resistance and geology adaptability, and the slope ration adopted 1:1.3 or 1:1.4 with experience. But this empirical design ratio might not be suitable to high CFRD, and the analysis of slope stability should consider the effect of dam height and slope ratio. In the typical division of CFRD proposed by Cooke, the scale of"dead zone"was not exactly designed, and there was no referable deformation modulus ratio between main and secondary rockfill zone. Owning to the complex stress-deformation characteristics of high CFRD, this question should also be discussed particularly.The effect of dam height and dam slope to slope stability were analyzed in this article with the limit equilibrium method and strength reduction method based on FEM and the expressions of dam height & stability factor and slope ratio & stability factor were proposed; the effects of the boundary ratio and the deformation modulus ratio between main and secondary rockfill zone to stress-deformation characteristics were studied and the reasonable scale of the boundary ratio and the deformation modulus ratio were suggested, which both meet the stability requirement and make full use of the rockfill materials to achieve the economical efficiency. The main content are as follows:(1) With the STAB program based on the limit equilibrium method (LEM), the stabilities of typical height dams (150m,200m,250m,300m) and slope ratios (1:1.4,1:1.5,1: 1.6,1:1.7) were analyzed under different operating times, the expressions of dam height & stability factor and slope ratio & stability factor was obtained by linear regression with a favorable correlation, which provides reference to the slope and dam height design of high CFRD.(2) Through strength reduction method based on FEM, the stabilites of dams (dam height 300m, dam slope 1:1.4under different operating times) were studied, according to the Mohr– Coulomb equivalent area circle yield criterion . The results implied that the stability factor were close to the results of LEM, which also proved the rationality of expression in content 1.(3) The effect of boundary ratio between main and secondary rockfill to stability for the maximum section, the effect of typical boundary ratio and the deformation modulus ratio between main and secondary rockfill to stress-deformation characteristics of high CFRD were studied. The rational range of boundary ratio and the deformation modulus ratio were pointed out to provide some references for the section division optimization and rational utilization of excavated materials for CFRD.