Mohammad Ebrahim Banihabib; Mohammad Hossein Poormohamadi
Volume 2, Issue 3 , October 2010, , Pages 123-132
Abstract
When upstream water surface of an earth dam falls down rapidly and the upstream slope of the dam cannot be drained, the rapid drawdown analysis is necessary. There are several methods for rapid drawdown analysis including; Bishop, Ordinary, Janbu, Morgenstern-Price, Spencer, Lowe-Karafiath, United State ...
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When upstream water surface of an earth dam falls down rapidly and the upstream slope of the dam cannot be drained, the rapid drawdown analysis is necessary. There are several methods for rapid drawdown analysis including; Bishop, Ordinary, Janbu, Morgenstern-Price, Spencer, Lowe-Karafiath, United State Army Corps of engineers (USACE) and modified USACE. Modified USACE is presented by Lowe and Karafiath and is modified by Duncan, Wright and Wong. For simulation two models of SEEPE/W and SLOPE/W, are used. Drawdown velocity of 1, 2, 4 and 6 m/day are used in simulation. Simulations show that increasing drawdown velocity causes decreasing safety factor. Rapid drawdown analysis by Bishop, Morgenstern-Price, Spencer, Lowe-Karafiath, USACE and modified USACE give the same results for safety factor. Safety factor of rapid drawdown analysis will decrease 26% compared to steady state analysis on the average.
Seyed Ali Asghar Hashemi; Mahmood Arabkhedri
Volume 2, Issue 1 , May 2010, , Pages 25-34
Abstract
Evaluation of empirical models for sediment yield in watersheds is a necessity. One of the conventional models in Iran is MPSIAC that has been used extensively. Sediment measurement of small dam's reservoirs is one of the methods for evaluation of these models. In this research, 9 small watersheds were ...
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Evaluation of empirical models for sediment yield in watersheds is a necessity. One of the conventional models in Iran is MPSIAC that has been used extensively. Sediment measurement of small dam's reservoirs is one of the methods for evaluation of these models. In this research, 9 small watersheds were selected in Semnan Province. There is an earth small dam at the outlet of each watershed built in the past 10 years. These dams have not spilled since they were built. Therefore total sediment volume discharged from each watershed was entrapped behind the dams. The amount of deposited sediments in these reservoirs was measured by surveying and estimation of apparent Specific Weight which then compared with estimating values of MPSIAC model by paired t-test. The results showed that the difference between the means for estimated volumes of sediment yield by use of MPSIAC model at the level of 5% had no significant difference while the difference between mean weights of sediments at the level of 5% was significant. Also determination of performance and relative root mean square error showed that MPSIAC model has no appropriate efficiency for application in the region.
