Statistical Analysis And Numerical Simulation Of The Behaviour Of Concrete Face Rockfill Dam Under Complicated Geological Conditions

Due to the low cost,adaptability to geological conditions and its ability to make full use of local materials,CFRD has become the most competitive dam type.The current construction of CFRDs often faces the challenge of complex geological conditions,such as narrow valley,severe cold,high earthquake and deep overburden foundation.Currently,CFRDs construction is faced with complex geological conditions such as narrow valleys,severe cold,strong earthquakes and deep overburden foundation.The deep overburden is a typical complex geological condition,which widely distributed in rivers in Southwest China.For the CFRD,the deformation control of the dam body is one of the most important considerations.The structural cracking and crushing of the face slab,the opening displacement of the joint and the safety and stability of the dam are both closely related to the deformation of the dam body.How to effectively and reasonably evaluate and control the deformation of CFRD is the most crucial factor that determines the further development of CFRD.In this paper,the methods of statistical analysis,multivariate nonlinear regression analysis and numerical simulation are used to systematically study the mechanical behaviour of the CFRD and concrete cutoff wall under complex geological conditions.The main research contents are as follows:(1)The deformation,stress and leakage behaviour of CFRDs were summarized from the perspective of statistical analysis.A set of monitoring records and construction details of 87 case histories of in-service CFRDs constructed in the past 50 years was collected.Detailed statistical analyses of crest settlement,settlement of the dam body,face slab behaviour and leakage after reservoir filling were conducted on the basis of the above-mentioned case histories.The statistical laws of the behaviour of CFRDs and several suggested empirical relationships were obtained by regression analysis to estimate the deformation and seepage behaviour of CFRDs.The correlation between dam deformation characteristics and its influencing factors was studied empirically.The statistical analyses also attempt to identify quantitatively the major influencing factors of the deformation of the CFRDs.(2)The multivariate nonlinear regression model was used to establish the empirical relationships between three deformation characteristics(including crest settlement,internal settlement,face slab deflection)and six control variables(including dam height,void ratio,foundation conditions,rockfill strength,valley shape,operation time).The obtained empirical relationships were compared with those of existing empirical methods and the relative importance of each control variable on the dam deformation behaviour was evaluated.(3)A parameter inversion analysis model of CFRD considering the creep and hydro-mechnical coupling effects of rockfill and foundation was established.The exact mechanism of the effect of the river gravel foundation on CFRD behaviour was discussed.The behaviour of the CFRD built on river gravel foundation was analysed comprehensively on the basis of in-situ masurement records and numerical analysis.A discussion of behaviour,especially with relevance to the behaviour of dams built on stiff-foundation,was included.The effect of various factors on the behaviour of the CFRD was also studied.(4)The deformation,stress and cracking behaviour of the concrete cut off wall were summarized from the perspective of statistical analysis.A set of monitoring records and construction details of 43 case histories of in-service concrete cut-off wall constructed in the past 50 years were gathered.Detailed statistical analyses of horizontal displacement,crest settlement,cracking behaviour and stress of the walls for CFRDs were performed.The mechanical behaviour difference between the walls for CFRDs and corewall dams was discussed in-depth.Loading characteristics of the wall were analysed.The statistical analyses also attempted to identify quantitatively the major factors affecting the wall behaviour.(5)A plastic damage analysis model of concrete cut off wall is established by considering the interface between the wall and adjacent soil and the hydraulic hydro-mechnical coupling effects of the foundation.Load mechanism,stress and deformation behaviour,and damage distribution and cracking for the cutoff wall of CFRDs were analysed on the basis of in-situ masurement records and numerical analysis.A discussion of the wall behaviour,especially with relevance to that of walls for dams with core walls,was included.The effect of several factors on wall behaviour was also discussed.