Abstract
In order to understand the hydrological process of expansive soil slopes, simulated rainfall experiments were conducted to study the effects of slope gradient and initial soil moisture content on runoff and infiltration for expansive soil slopes located in south China. The field program consisted of four neighboring slopes (70%, 47%, 32%, and 21%) instrumented by a runoff collection system and moisture content sensors (EC-5). Results from the monitored tests indicate that there was delay in the response of surface runoff. The runoff initiation time decreased with initial soil water content and increasing slope gradient. After the generation of runoff, the cumulative runoff per unit area and the runoff rate increased linearly and logarithmically with time, respectively. The greater the initial soil moisture content was, the smaller the influence of slope gradient on runoff. A rainfall may contribute from 39% to about 100% of its total rainfall as infiltration, indicating that infiltration remained an important component of the rainwater falling on the slope, despite the high initial soil water content. The larger the initial sealing degree of slope surface was the smaller the cumulative infiltration per unit area of the slope. However, the soil moisture reaction was more obvious. The influence of inclination is no longer discernible at high initial moisture levels. The greater the initial soil moisture content and the smaller the slope gradient, the weaker was the change of soil water content caused by simulated rainfall. The influence of initial soil moisture content and slope gradient on the processes of flow and changes of soil water content identified in this study may be helpful in the surface water control for expansive soil slopes.
Highlights
Expansive clay is a special soil formed in the natural geological process with obvious swelling and shrinkage, distributed in more than 40 countries and regions [1]
The results demonstrated that rainwater infiltrates into the expansive soil slope and the soil expands by absorbing water, leading to changes in stress, deformation, permeability, and shear strength of the slope
2019,and several simulated were carried out in the to studysoil the influence of slope gradient initial moisturerainfall contenttests on runoff and infiltration forsite expansive influence of slope gradient and initial moisture content on runoff and infiltration for expansive soil slopes
Summary
Expansive clay is a special soil formed in the natural geological process with obvious swelling and shrinkage, distributed in more than 40 countries and regions [1]. The failure of expansive soil slopes was a common problem in the rainy season. Chen et al [4] analyzed the influence of water infiltration and fracture on the deformation of expansive soil slopes with different densities using centrifugal model tests and found that rainwater was responsible for the slope failure. Ng et al and Zhan carried out artificial rainfall simulation tests on an 11 m high cut slope in a typical medium-plastic expansive clay [5] and studied the interaction between expansive soil and water [6]. The results demonstrated that rainwater infiltrates into the expansive soil slope and the soil expands by absorbing water, leading to changes in stress, deformation, permeability, and shear strength of the slope. Qi and Vanapalli [7] evaluated
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