Stress And Deformation Analysis Of Concrete-faced Rockfill Dam Under Complicated Geological And Topography Conditions

Some concrete-faced rockfll dams(CFRDs)will be built on deep alluvium,deep channel,riverbed terrace and high steep slope with the development of hydropower proj ects.The construction of CFRD under complicated geological and topography conditions has become new challanges for CFRD construction.The stress and deformation are more complicated for CFRD under complicated geological and topography conditions.In this study,based on the analysis of the deformation behavior of some completed CFRDs,the nonlinear finite element method is used to analyze the stress and deformation characteristics of CFRDs on deep alluvium and reverbed terrace.The load characteristics of cut-off wall in deep alluvium is disscussed.The stress and deformation characteristics of different material cut-off walls are analyzed.Finally,a CFRD is selected as a case study,which dam site exists deep channel,reverbed terrace and deep alluvium.Two processing schemes are designed for reverbed terrace.Finite element analysis is carried out to compare CFRD behavior differences of two processing schemes.The main research contents and conclusions of this paper are as follows:(1)The deformation behavior of some completed CFRDs on deep alluvium and complicated topography conditions is analysed.The results indicate that the maximum settlement positions of CFRDs built on deep alluvium are generally below 0.4 times the dam height in our country,and the maximum settlement position offsets to the bottom of the dam with the thickness of alluvium increasing.The face slab cracks mainly occur at the slope transition or the undulation of foundation pit.(2)Three-dimensional finite element models of CFRD on deep alluvium and reverbed terrace are established.The stress and deformation of CFRD are analyzed.The results suggest that the upstream horizontial displacement is smaller than downstream horizontial displacement at completion when the cut-off wall is used for anti-seepage of CFRD built on deep alluvium.The dam horizontial displacement point to the downstream and the maxmium settlement close to dam bottom after impoundment.The reverbed terrace has a supporting effect on its upper rockfill and face slab,so the axial displacement of its upper face slab is very small.The dam stress at the corner of the riverbed terrace is arched upward and is greater than other parts of the same elevation.There is stress concentration at the corner of face slab.(3)The load characteristics of cut-off wall in deep alluvium is revealed.The stress and deformation characteristics of different material cut-off walls are analyzed.The results indicate that cut-off wall in deep alluvium of CFRD is a combined bending and compression structure.The horizontial displacements of different cut-off wall do not show significant differences at completion.There is neutral point at downstream surface of ordinary concrete cut-off wall and low Young's modulus concrete cut-off wall at completion,and the position of neutral point close to the bottom of cut-off wall.The horizontal displacement increases significantly with the increase of cut-off wall flexibility during impoundment.The horizontial displacement of ordinary concrete cut-off wall is minimum,and that of high polymer cut-off wall is maximum after impoundment.(4)The case study indicates that the axial displacement distribution of the dam body is extremely asymmetrical under the influence of the riverbed terrace and the deep channel.It is effective to improve dam deformation and face slab stress when the rolling compaction dry lean concrete processing scheme is adopted.The settlement and horizontial displacement of dam on the reverbed terrace decrease obviously.The maximum settlerment position move up to dam crest and the distribution of dam axis displacement become more homogeneous.