Rainfall infiltration characteristics and numerical simulation of slope instability in the basalt residual soil in the coastal area of Southeast China
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摘要: 暴雨作用下，东南沿海地区玄武岩残积土滑坡极易失稳，但相关的研究较为少见。文章以浙江省温州市马济头滑坡为对象，首先利用原状土土柱实验，获取中峰型和前峰型降雨工况下玄武岩残积土的雨水运移特征；然后使用Geo-studio软件反演土柱降雨实验，获取玄武岩残积土的非饱和渗透参数；接着通过数值模拟，获取两种降雨工况下马济头滑坡的渗流场及稳定性。结果表明：降雨作用下，玄武岩残积土的浅层土体含水率增长速率较快，上部及深部土体更易达到饱和；10 mm/h降雨强度下，湿润锋下渗速率较小且不随深度变化；30 mm/h降雨强度下，湿润锋下渗速率可增大2~3倍，雨水主要在峰值降雨期快速入渗；降雨作用下，马济头滑坡的滑带土饱和度迅速增大，孔隙水压力随之增大，坡脚出现大面积滞水，土体抗剪强度急剧降低，模拟降雨第三天，滑坡的稳定性系数降至最低，滑坡最终失稳；中峰型降雨工况下雨水入渗速率更快，坡脚处产生更大滞水面积，滑坡更容易失稳。本文的研究成果可为东南沿海玄武岩残积土滑坡的稳定性评价提供理论依据。Abstract: Slopes in the basalt residual soil in the coastal areas of southeast China are easy to fall during the typhoon rainstorm. However, this aspect was seldom examined. In this paper, the Majitou landslide is chosen as a sample, and the undisturbed soil column tests are conducted to get the rainwater migration and distribution characteristics of the basalt residual soils under the central and advanced rainfall conditions. Geo-studio software is used to retrieve the soil column tests to obtain the unsaturated seepage parameters of the soil. The above results are applied to the numerical simulation to obtain the seepage field and slope stability of the Majitou landslide under the two rainfall conditions. The results indicate that the volumetric water contents in the upper and bottom parts of the soil column increase greatly during rainfall; under the rainfall intensity of 10 mm/h, the migration velocity of wetting front is low and unchanged with depths; while under the rainfall intensity of 30 mm/h, the migration velocity is 2-3 times greater than the former and decreases gradually with depth. Rainwater rapidly enters the basalt residual soil during the peak rainfall, and after three days’ rainfall, the soil saturation and the pore-water pressure of the Majitou landslide increase rapidly. The perched water appears at the foot of the slope, the soil shear strength decreases sharply, and the slope is unstable. The rainwater movement velocities under the central rainfall conditions are faster, which lead to the larger perched water area, and the landslide is easier to induce. The results in this paper may provide theoretical background for the stability evaluation and treatment for slopes in the basaltic residual soil in the coastal regions in southeast China.
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Key words:
- residual soil slope /
- landslide /
- soil column test /
- seepage field /
- stability assessment /
- numerical simulation
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