| Recent years, extreme meteorological conditions appear frequently, people start to pay attention to it for the severe test to surviving. Since the construction of the Three Gorges Reservoir, the migrant is about 110.56 million and resettle area is 15000km2 in the reservoir area, include 13 cities, 116 towns move all or part. Great amount of engineering spoil accumulated while relocating, and is dumped on the slope directly, landslide may be caused and make impact on life and property of residents in resettlement areas under extreme meteorological condition. Therefore, research of responsive mechanism between landslide of engineering spoil accumulation and extreme meteorological condition is an important issue. Based on the results of previous studies, take example of engineering spoil accumulation in the Three Gorges Reservoir in Chongqing, combined with research methods of experiment, theoretical analysis, numerical simulation, analyzed the changing relationship of saturation line, pore water pressure, infiltration depth with rainfall intensity, rainfall duration and void ratio in engineering spoil accumulation slope under the extreme rainfall, got the transient stability coefficient by calculating the stability of engineering spoil accumulated landslide under various void ratios and rainfall conditions though the unmodified and amended stability formula , and compared the results of two formulas. The main contents and results are as follows:First, analyzed the latest researching all of the word and parameter experiment of particle curve, natural bulk density, shear strength parameters and soil-water characteristic curve, experiment shows that the engineering spoil is fine-grained gravel soil; saturated permeability coefficient increased as well as void ratio, and the increasing trend is moderate as void ratio is less than 0.7 but increased rapidly as it is greater than 0.7.Take 60% saturation for the boundary, soil cohesion increased as saturation is less than 60%, decreasd rapidly as it is more than 60% , and reached to the peak near 60%. Trend of soil internal friction angle ? value decreased slowly at first, rapidly then, slowly again ,rapidly at last as saturation increased from 20% to 40%,40% to 60%,60% to 80%, and more than 80%. Matric suction increased as void ratio decreasing in the same saturation, and decreased as saturation increasing in the same void ratio, , and the value is no longer effected by compaction density when saturation reached to 80% , When the void ratio is greater than 0.7081, the soil-water characteristic curve changed with saturation unobviously.Second, based on the strength theory of unsaturated soil, derived simple Sweden arc method from modifying the traditional formula of Sweden arc method to make it can be used in stability calculation of saturated slope as well as unsaturated slope.Third, according to the most extreme rainfall over the years in the Three Gorges Reservoir area, assuming slope of engineering spoil accumulation experienced 4 days of antecedent rainfall (25mm / d) and 2 days of extreme rainfall (100mm / d, 200mm / d, 300mm / d) continuously, obtained distribution of the pore water pressure of each time by using GEOSTUDIO (2004) software calculated the flow process in the slope of engineering spoil accumulation under the given boundary conditions. Numerical results show that: the relationship between the extreme rainfall intensity and permeability and rainfall duration are the parameters which have a significant effect on pore water pressure. Depth of rainfall infiltration is greater as extreme rainfall intensity and permeability coefficient are greater when bearing the same early rainfall and same rainfall duration. And the changing of pore water pressure in engineering spoil accumulation at the foot of the slope is severer than the shoulder, and the effect by extreme rainfall is the most obvious.Fourth, depending on the water content and value of pore water pressure of each node at the different time, stability coefficients of each moment were calculated by using method of Sweden arc method in specification and modified Sweden arc method , results shows : the stability calculated by modified formula is higher than unmodified formula ,the rate is 0.245-0.293. When the void ratio of unsaturated soil slope is 0.7081:1)The stability coefficients of engineering spoil accumulated landslide of unmodified and modified formula in terms of less than 1.000 and 1.062 under extreme rainfallⅠfor 45.6 and 48 hours .2)The stability coefficients of engineering spoil accumulated landslide of unmodified and modified formula in terms of less than 1.000 and 1.023 critical stability under extreme rainfallⅡfor 40.3 and 48 hours .3)The stability coefficients of engineering spoil accumulated landslide of unmodified formula is less than 1 under extreme rainfallⅢfor 36 hours; and modified formula changed the time from 36 to 44.5 hours , increased 8.5 hours, matric suction of unsaturated soil slope played role fully , results close to reality... |
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