土水特征曲线在滑坡预测中的应用性探讨

ON APPLICATION OF SOIL-WATER CHARACTERISTIC CURVES TO LANDSLIDE FORECAST

通过模型试验与数值分析方法的结果对比,研究土水特征曲线中的主要增湿路径与主要减湿路径对降雨型滑坡预测的影响。研究结果表明,采用不同状态路径的土水特征曲线来进行降雨条件下边坡的有限元渗流分析,会得到不同的基质吸力和孔压变化趋势,进而影响强度折减有限元法的计算结果;而对于相同的基质吸力条件下,采用主要增湿路径所预测的非饱和渗透系数会低于主要减湿路径的预测值,使得主要减湿路径预测滑坡破坏时间较主要增湿路径快。此外,若边坡产生滑动型破坏,则实际滑坡发生时间在主要减湿路径与主要增湿路径的预测值之间。研究成果说明,采用作为界限的主要增湿和主要减湿路径作为土水特征曲线的滞后模型,对降雨型滑坡灾害的防灾预警具有一定的实用价值,可利用主要增湿与减湿路径预测滑坡发生的时间差,规划与建立合适的滑坡雨量预警基准。

The determination and application of soil-water characteristic curves（SWCCs） are key issures for unsaturated soil mechanics in geotechnical engineering practice. Unfortunately, it is hard to use in practice owing to the complexity of SWCCs. Hence, the landslide model tests for soil slope under artificial rainfall and numerical analyses are used to study the practicability of main drying and wetting curves in SWCCs. In the numerical analyses, the pore water pressure in slopes is calculated by the finite element analysis of water flow through unsaturated-saturated soils; and the slope stability is evaluated by finite element method in consideration of shear strength reduction technique. The results show that the actual occurrence time of landslide is between the evaluated time of main drying curve and main wetting curve in general condition; and the occurrence time of landslide which is evaluated by main drying curve is shorter than main wetting curve. It is implied that the main drying curve and main wetting curve can be used to build rainfall warning criteria for rainfall-induced landslide hazards. Consequently, the main drying and wetting curves of SWCCs are the most significant simplified hysteresis model for unsaturated soil slope seepage numerical analysis. Because the main drying and wetting curves represent the two boundaries of soil state path; it is appropriate for using these two boundary curves to build up rainfall warning criteria of landslide hazards for specific mitigation purpose such as emergency response.