降雨-蒸发循环作用下膨胀土填方边坡变形特征与机理研究

Study on deformation characteristic and mechanism of expansive soil fill slope under precipitation-evaporation cycle

为了对安康膨胀土地区拟建机场工程设计提供必要的基础参数,特在该场地建立了填方边坡稳定性的现场物理试验模型;跟踪测试了边坡在降雨-蒸发循环作用下的一系列变形,进而分析了其演化规律与成因机制。结果显示:(1)新建填方边坡的雨水入渗过程由自由入渗、冲刷入渗及稳定入渗3个阶段组成。在本次试验中;雨水入渗过程大部分处于冲刷入渗阶段,导致其入渗深度有限。(2)对于完整均匀的填方边坡,其变形的发展受到土体膨胀变形的主导作用;在坡顶主要表现为竖直向的胀缩变形;坡面则主要表现为水平向的累积变形;随着深度的加大、降雨次数的增加,变形速率急剧降低。(3)边坡的变形与降雨-蒸发作用密切相关,降雨作用是导致变形陡增的主要因素;蒸发作用是变形发展的必要前提条件。(4)防止边坡在降雨-蒸发作用下的变形破坏应从两方面着手:一是有效减弱其在边坡表层影响范围内土体湿度的变化,二是防止径流对坡面的冲刷、侵蚀作用。

An airport is planned to build in Ankang City where expansive soil distributes widely. In order to provide the necessary basic parameters for the project, a field physical test model of the stability of fill slope was built at the proposed site. a tracking test series of deformation of expansive soil fill slope under precipitation-evaporation cycle were conducted, and the the deformation evolution law and cause mechanism were analyzed. The results show that： （ 1 ） Stormwater infiltration process of the new fill slope can be divided into three stages ： free infiltration, scouring infiltration and stable infiltration. In this test, most time of the rain infiltration process is scouring infiltration stage, resulting in limited a infiltration depth. （2） For a complete uniform fill slope, the soil swelling deformation plays the leading role in the deformation development; at slope top the performance is vertical expansion and contraction deformation while at slope surface the performance mainly displays horizontal cumulative deformation. With the increase of the depth and rainfall frequency, the slope deformation rate decreases dramatically. （3） The deformation of slope is closely related to the action of rainfall and evaporation, in which rainfall is the main factor in slope abrupt change, evaporation is a necessary prerequisite for the development of deformation. （4） two approaches should be adopted in preventing deformation and failure of the slope in rainfall-evaporation： one is to effectively weaken the variations of the moisture of the soil mass in influenced range of its surface layer, the other is to prevent runoff scouring action on the slopes.