Research on Analysis Method for Stability of Perched Transient Saturated Slope
(2.Key Laboratory of Water-sediment Sciences and Water Disaster Prevention of Hunan Province, Changsha University of Science & Technology, Changsha, Hunan, China 410004)
(3.Water Resources Department of Hunan Province, Changsha, Hunan, China 410007)
(4.Shaoyang Hydro & Power Design Institution, Shaoyang, Hunan, China 422000)
【Abstract】In order to analyze the stability of the transient saturated slope caused by rainfall infiltration, the instability mechanism of transient saturated slope under the condition of rainfall infiltration was analyzed by considering the influence of unit weight, matric suction and transient water pressure. The distribution law of transient water pressure in the transient saturated area was discovered, and the corresponding computing methods for transient water pressure were proposed. A modification on Janbu limit equilibrium method with the consideration of transient water pressure, matric suction and great changes was made by dint of the distribution condition whether the slope was situated at the perched transient saturated area. And a routine which could search both circular and non-circular sliding surfaces was programmed for the stability analysis of transient saturated slope. The variation law of stability factor and sliding mechanism of perched transient saturation slope were investigated. The results show that the stability is mainly influenced by matric suction at the beginning of rainfall period, as the depth of transient saturated area is shallow. With the increase of the depth of the transient saturated area, transient water pressure in the slope becomes the main factor controlling the slope stability, and the safety factor of the slope gradually decreases. The safety factor of non-circular type is smaller than that of circular type with the increase of the depth of the transient saturated area. Besides, the potential sliding surface of non-circular sliding mode becomes shallower with the decrease of the depth of the transient saturated area. It is also indicated that under the same condition, the depth of non-circular sliding surface is always smaller than that of circular sliding surface with the increase of the depth of the transient saturated area. The depth of the most dangerous mansard sliding surface decreases with the increase of the transient saturated area. The depth of the circular sliding surface decreases first and then increases. This variation trend is related to the transient water pressure on the bottom of the slice and the shear strength parameters. A shallow non-circular slice mode is more easily generated in the perched transient saturated slope.
【Keywords】 road engineering; perched transient saturated slope; improved Janbu method; transient water pressure; instability mode;
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