Upper bound solution of slope stability analysis for“filling earth from #br#
upstream deposited silt”
WANG Hongyu1，2，YAN Chao1，CAO Jing1
(1. School of Civil and Hydraulic Engineering，Ningxia University，Yinchuan，Ningxia 750021，China；2. Engineering Research Center of Ministry of Education for Efficient Utilization of Modern Agricultural Water Resources in Arid Regions，Ningxia University，Yinchuan，Ningxia 750021，China)
Abstract：The stability analysis problem of the composite earth dam with multiple weak joints composed of soils in different consolidation states will be encountered when adopting the method of filling earth from upstream deposited silt which be common in northwest loess hill region for the reinforcement of the reservoir. Based on the upper bound theorem of plastic mechanics limit analysis，two destruction mechanisms have been constructed with the slope of filling earth from deposited silt as the research object that according to the structural type of composite earth dam and the operating characteristics of the reservoir. Then，considering the influence of the static water pressure of the dam slope and the pore water pressure in the earth caused by the dynamic change of the reservoir water level，the safety factors have been analyzed and optimized by using strength reduction technology and SQP method. On this basis，taking the reservoir reinforcement project of filling earth from upstream deposited silt from Ningxia southern mountainous area as a case，the upper limit solution of this paper and the numerical simulation results of Optum-G2 and Geo-studio have been compared and analyzed. The research results show the upper limit solutions of the two destruction mechanisms are very close to the numerical simulation values and the relative error of the safety factor is less than or equal to 5.7% when the reservoir water level drops sharply from the design water level to the dead water level. The failure mode change with the width of the weak interface of silt and new fill. The slope safety factor shows a nearly linear relation with the weak interface width variation that the safety factor will be increased about 2.7% as add every 1 m of interface width when the dam slope fails in translation. And the slope safety factor also has a nearly linear relation with the slope ratio variation that the slope safety factor will be reduced about 8.6% as add every 0.1 of slope ratio under rotation-translation combined failure conditions. The upper bound solution that presents in this paper is simple，convenient and suitable for the type of problem.
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2023, Vol. 42 
