Research On The Seepage Characteristics And The Stability Of High Side-slope With Thick Covering Layer Under The Condition Of Rainfall Infiltration

The construction of highways has developed rapidly, but its construction in mountain areas has confronted with challenges such as landslide and high side-slope deformation, which are usually caused by the complexity of topography and geological conditions. Problems of landslide and high side-slope deformation not only increase investment and construction periods, but also cause natural disasters. The instability and slump of side-slope, one of three major geological disasters around the globe, has seriously endangered the state property and human beings’ lives. This thesis will choose the left thick layer of the high side-slope in Liuzhou to Nanning K1251+000～K1251+180 section of the Quanzhou to Nanning highway as its research object. According to the actual situation of the project, the research on the seepage characteristics of slope and its stability will be carried out by Geo-studio numerical simulation software. The main achievements of this thesis are as follows:(1) The intensity of the rainfall can affect the internal saturation line of slope, which further causes the safety factor of slope. In the continuous rainfall process, the non-saturated region of high side-slope in the covering layer will shrink to "O" shape. As the heavier the rainfall is, the smaller the "O" shape appears. In the initial period of rainfalls the safety factor of side-slope is in slight decline, while the continuous rainfall will affect the descend range of the safety factor of side-slope. After the rain stopped, the safety factor of side-slope will firstly increase and then decrease. Short-term heavy rainfalls exert great influence on the stability of high side-slope with thick cover.(2) The lighter the covering layer is, the change of the saturation line in the foot of the side-slope appears, and the larger the transient saturated zone and unsaturated zone within the slope are. The safety factor of slope is inversely proportional to the thickness of the covering layer. In other words, the larger the area of covering layer is, the smaller the safety factor of slope is, and the slower the descend range of the safety factor of slope is.(3) When the soil permeability coefficient of the covering layer is smaller than a certain value, the bigger the soil permeability coefficient of the covering layer is, the shorter the time spent in the accumulation of the volumetric water content will be, and the greater the descend range of the seepage line will be. As the soil permeability coefficient continually increase, the seepage line in the surface of the slope will be no longer connect with the seepage line at the foot of the slope, and the seepage line in the surface of the slope will gradually disappear. When the soil permeability coefficient of the covering layer is larger than a certain value, the seepage line of side-slope is only formed at the bottom of slope bedrock. As the soil permeability coefficient in the covering layer increases, the seepage line of side-slope decrease. Under the same rainfall intensity, if the soil permeability coefficient of the covering layer becomes big, the safely factor of the side-slope will in decline, and it is its descend range.(4) Anchor can effectively improve the stability of the covering layer of high side-slope. When anchor’s anchorage section does not deeply insert into the bedrock, the longer the anchor is, the bigger the safety factor of side-slope is, and the higher the slope stability is. When anchor’s anchorage section deeply inserts into the bedrock, the length of the anchor will not affect the safety factor of side-slope and the slope stability. Besides, anchor’s anchorage section can have a great influence on the stability of the covering layer of high side-slope.