Abstract
Newmark sliding block approach has been extensively studied by many researchers in the past decades. Significant progress has been made to alleviate its deficiencies and overcome its simplifying assumptions, but some aspects such as the cyclic shear strength and time history vertical acceleration in the Newmark sliding displacement analysis are seldom considered strictly. In the presented research, a modified Newmark methodology for sliding deformation analysis of rock-fill dams subjected to strong earthquake is proposed. In order to make the seismic safety evaluation of dams more realistic, the influence of cyclic shear strength (earthquake-induced reduction of shear strength) and time history vertical acceleration obtained from the dynamic response analysis on the critical acceleration and accumulative sliding displacement of the flexible sliding body is considered. Detailed comparison between the proposed method and existing methods is performed via the analysis of two typical dams, that is, a virtual rock-fill dam with a height of 100 m which is assumed to be situated on rock formation and a real core rock-fill dam with a height of 150 m built on deep overburden layers. It is demonstrated that the cyclic shear strength and time history vertical acceleration within flexible sliding body, as highlighted in the proposed method, have significant effect on the seismic safety evaluation, critical acceleration, and accumulation of sliding deformation of rock-fill dams subjected to strong earthquake loading. The existing approaches tend to provide unconservative evaluation on the consequences of earthquakes on rock-fill dams.
Highlights
Nowadays, the evaluation on the seismic performance of rock-fill dams and Earth slopes subjected to strong earthquakes is performed utilizing the traditional forceoriented factor of safety, and the magnitude of the accumulative earthquake-induced sliding displacement [1,2,3]
From the engineering point of view, the accumulation of sliding displacement, which is regarded as a key index for the safety evaluation of high core rock- ll dams subjected to design earthquake, obtained by the traditional method tends to be unsafe as the e ects of cyclic strength and time history vertical acceleration on the critical acceleration are ignored
A modi ed Newmark-type methodology for sliding deformation analysis of rock- ll dams subjected to strong earthquake is developed. e e ects of cyclic shear strength and time history vertical acceleration on the sliding displacement are considered in detail
Summary
The evaluation on the seismic performance of rock-fill dams and Earth slopes subjected to strong earthquakes is performed utilizing the traditional forceoriented factor of safety, and the magnitude of the accumulative earthquake-induced sliding displacement [1,2,3]. 2. Cyclic Shear Strength of Rock-Fill Materials e first aim of this study is to analyze the effect of cyclic shear strength on earthquake-induced sliding displacements using the modified Newmark method in order to improve the ability of predicting seismic stability of rock-fill dams. For some particular rock-fill dams, such as rock-fill dam with clay core, sand gravel dam, and rock-fill dam built on the saturated clay or sandy deposits, the impact of cyclic shear strength on the critical acceleration and accumulation of sliding displacement would be so significant that it must be carefully considered as the liquefaction does not occur For this purpose, available data of dynamic triaxial tests on cyclic shear strength of rock-fill materials were analyzed and a correlation between cyclic shear strength and number of cycles was obtained and listed in Tables 3 and 4
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