Abstract
It can be a great expense to examine individually the stability of earth and rockfill dams on rapid drawdown in civil engineering practice. The aim of this present work is to clarify the safe type on the rapid drawdown among the most common types of earth and rockfill dams and to introduce cheaply the types in dam design. First, a transient analysis of saturated-unsaturated seepage coupled with stress is carried out in the cross sections of typical earth and rockfill dams the during rapid drawdown, and the safety factors of the upstream slopes are determined by the shear strength reduction method. Then, the typical dams are compared for the stability characteristics so that designers can select the safe type of earth and rockfill dams on rapid drawdown. The obtained results show that the decreasing rate of safety factor in a central core dam is 0.72–0.85 times than one of the homogeneous dams and 0.17–0.40 times than one of the sloping upstream core dams so that it is more stable than other earth and rockfill dams during rapid drawdown.
Highlights
Khanna et al [3] analyzed the stability of the central core dam of 180m height to show that the safety factor of the upstream slope under RDD remains high when the thickness of the vertical core is less than 150% of the height of the dam, and Boushehrian et al [4] presented that the horizontal drains in the upstream slope of the dams increase the safety factor of the upstream slope up to 24% for homogeneous dams and 17% for heterogeneous dams
Pinyol et al [6] compared the predictions of four calculation procedures with pore pressure records measured in Glen Shira dam during a controlled drawdown and presented that only the coupled analysis provides a consistent and reasonable solution, and Chen and Huang [7] presented that the strength reduction method used in FEM is very effective in capturing the progressive failure induced by reservoir water level fluctuations
It is assumed that saturated-unsaturated transient seepage occurs in ERDs, and the shear strength of soils in the unsaturated zone is a function of the degree of saturation
Summary
E stability of the slopes was analyzed by using the shear strength reduction method with ABAQUS-6.14. e element type of CPE4P was used in the analysis, and elements of about 500 were taken in each ERD. E effects of the mesh on the stability of ERDs do not be considered in the present work because a relationship curve between horizontal displacement and reduction factor is employed in order to obtain the safety factor of ERDs. e results of finite element analysis affect the mesh and especially stress and strain. It seems that the effects of the mesh on the displacement are not large so that the position of the inflection point on the relationship curve between horizontal displacement and reduction factor is almost unchanged depending on the mesh. 4.2. e Stability Reduction Characteristics. e stability matter of the ERDs during RDD is ascribable to a stability (a)
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