土木工程降雨條件下坡積土邊坡暫態飽和區形成機理及分布規律

付宏淵　史振寧　曾鈴

摘要：

降雨是引起坡積土邊坡失穩的最常見外部因素之一。雨水的入滲在引起土體抗剪強度參數降低的同時，還將導致土體重度的增加、基質吸力的降低，最終造成邊坡的失穩。開展雨水在邊坡內部的滲流過程研究已成為分析邊坡在降雨條件下穩定性的前提。基于有限元數值模擬方法，進行了雨水在土體中滲流過程的模擬，著眼于降雨條件下邊坡暫態飽和區的形成、分布及消散特征，描述了該過程中邊坡內部含水率、基質吸力、水力梯度的變化規律。結果表明：暫態飽和區形成的主要原因是土體中向濕潤鋒下方滲出的雨水量小于降雨入滲補給量，從而使得土體中的含水率累積升高；暫態飽和區的形成與降雨強度、降雨時間具有十分密切的關系，暫態飽和區形成時間、雨水入滲深度、土體表面體積含水率大小分別與降雨強度存在函數關系；清晰描述了暫態飽和區形成發展消散地下水位升高的全過程，從該過程看，邊坡排水措施的設計值得思考。

關鍵詞：

邊坡工程；坡積土邊坡；降雨入滲；數值模擬；暫態飽和區

中圖分類號：TU457

文獻標志碼：A文章編號：16744764（2017）02000110

Abstract：

Rainfall is one of the most common external factors causing the instable residual soil slope. Rainwater infiltration leads to the reduction of the soil shear strength， the increase of the weight of soil and the decrease of the matric suction， so as to cause the slope instability. The study of rainfall infiltration inside the slope has become the precondition of the study of the slope stability under the rainfall condition. Basing on the finite element numerical simulation method， this paper focuses on the simulation of rainfall infiltration process. The present work is emphasized on the formation， distribution and vanishing of transient saturated zone， and characterizes the variation of volume water content， matric suction and the hydraulic gradient inside the slope. The results can be the foundation of the study that the rainfall influences the stability of residual soil slope. The calculation results show that： 1）The major cause of the formation of transient saturated zone is ascribed to the fact that the rainwater exudation under the wetting front is less than the amount of rainfall infiltration， thus increasing the moisture content in the soil； 2）The formation of transient saturated zone， rainfall infiltration depth and the water content of soil surface have close relationship with rainfall intensity and duration. The entire process from the formation， to the development， to the vanishing of transient saturated zone， and to the raise of groundwater level is studied. From the design of slope drainage is worth thinking is indicated.

Keywords：

slope engineering； residual soil slope； rainfall infiltration； numerical simulation； transient saturated zone

邊坡失穩與許多因素有關，現場監測及理論研究結果表明[1]：邊坡失穩主要與水文地質條件、氣候因素以及人為削坡等單個或多個因素有關。近年來，隨著中國高速公路建設的大力推進，出現了大量人工開挖路塹邊坡，且表面具有一定厚度的第四系堆積土，這些邊坡在人為擾動與降雨影響下極易發生失穩破壞。……