人工降雨条件下黄土边坡的室内模型试验研究

发布时间：2018-06-12 14:03

本文选题：黄土 + 滑坡　；参考：《西北农林科技大学》2013年硕士论文

【摘要】：在我国，黄土和黄土状土广泛分布，总面积约为64万m2。黄土滑坡地质灾害频繁发生，以其大规模、强危害、难预测、难治理等特点严重威胁着人民生命财产安全，限制着黄土地区经济和社会发展。另外，黄土高原普遍存在坡面侵蚀问题，主要发生在降雨较多的6—9月，黄土坡面会遭受严重破坏，进一步引发水土环境恶化及土壤养分流失，降低土地生产力。降雨等引发的水分入渗对边坡的破坏作用是显而易见的，坡面冲蚀也是由降雨引起，鉴于此，为进一步保障人民生命财产安全，本文将开展针对降雨这一主要诱因对黄土滑坡和坡面侵蚀的影响的试验研究。本文自行研制人工降雨装置，并建立了黄土边坡的室内模型，所用黄土土料取自陕西杨凌。通过人工降雨条件下黄土滑坡及裸坡坡面形态变化的试验研究，，利用水分传感器、应力传感器、示踪点、数码拍摄等综合监测，观察了强降雨条件下黄土滑坡的发生发展过程以及坡面形态的变化情况。试验的主要内容及结论如下：（1）通过在边坡内部埋设的水分传感器获得坡体内部实时含水率，并在有机玻璃一侧观察湿润峰情况。由此可知，水分入渗速率随时间变化由快到慢，坡顶的水分入渗速率始终大于坡面的；水分径流量和入渗量的比值随时间先增大再减小最终趋于稳定；坡体内部含水率由上到下依次开始增大，其值增大到一定水平后趋于平稳，标志着该位置土体近似饱和，模型发生滑坡时最大体积含水率约为41%~44%。（2）60°模型内部埋设微型压力盒测量不同位置的应力值。可知，某一位置的应力与其深度有关，深度越深应力越大；应力发展与时间有关，累计时间在t=400min~700min之间时应力值波动最大，据此可知该时间段有可能是滑坡形成的关键期。（3）通过示踪点、小红旗、棉线等实现位移监测并对表面现象如裂缝等进行观察记录。可知，坡体有向下和向前两个方向的位移，坡顶下方位移方向与竖向所成角度约为0~10°，最大位移约10cm；坡面下方位移方向与竖向所成角度约为30°~60°，最大位移约15cm；降雨过程中坡顶首先产生贯通的拉裂缝，水分进一步入渗后坡体内部产生局部微小竖向裂缝。（4）利用数码设备记录边坡整体变化和坡面形态变化等，以45°模型试验为例可知，其坡面侵蚀经历了“片蚀—沟蚀—沟间坡面面蚀向深切和侧蚀发展”的过程，后期形成较大冲蚀沟并且沟岸发生崩塌；坡面因受侵蚀呈整体下降趋势；降雨使得坡趾处土体饱和程度较高，小型滑塌自下而上发展，边坡土体的坡面崩滑位置逐渐向上推移，最终发生大规模坡面崩滑。
[Abstract]:Loess and loess soil are widely distributed in China, with a total area of about 640000 m2. The frequent occurrence of loess landslide geological hazard is a serious threat to the safety of people's life and property and restricts the economic and social development of loess area because of its large scale, strong harm, hard to predict, difficult to manage and so on. In addition, slope erosion is a common problem in the Loess Plateau, which mainly occurs in the June to September rainfall. The loess slope will suffer serious damage, which will further lead to the deterioration of soil and water environment and soil nutrient loss, and reduce the land productivity. The effect of water infiltration caused by rainfall on the slope is obvious, and the erosion of the slope is also caused by rainfall. In view of this, in order to further ensure the safety of people's lives and property, In this paper, the influence of rainfall on loess landslide and slope erosion will be studied. In this paper, the artificial rainfall device is developed, and the indoor model of loess slope is established. The loess soil material is taken from Yang Ling of Shaanxi province. Through the experimental study on the morphological change of loess landslide and bare slope under artificial rainfall, the comprehensive monitoring is made by using water sensor, stress sensor, tracer point, digital photography and so on. The occurrence and development process of loess landslide and the change of slope shape were observed under the condition of heavy rainfall. The main contents and conclusions of the experiment are as follows: 1) the real time moisture content of the slope is obtained by the moisture sensor embedded in the slope and the wet peak is observed on the side of organic glass. It can be seen that the water infiltration rate changes from fast to slow with time, the water infiltration rate at the top of the slope is always larger than that on the slope, and the ratio of water runoff and infiltration volume increases first with time and then decreases and then tends to stabilize. The moisture content of the slope begins to increase from top to bottom, and the value increases to a certain level, which indicates that the soil is approximately saturated in this position. The maximum volume water content of the model is about 41 / 44 when the landslide occurs. The stress values of different positions are measured by embedding a micro pressure box inside the model. It can be seen that the stress in a certain position is related to its depth, the deeper the stress is, the greater the stress is, and the stress development is related to time, and the stress value fluctuates most when the cumulative time is between t=400min~700min. It can be concluded that this time period may be the key period of landslide formation. (3) displacement monitoring is realized by tracing points, small red flags, cotton thread and so on, and surface phenomena such as cracks are observed and recorded. It can be seen that there are downward and forward displacement in the slope, the angle between the displacement direction and the vertical direction is about 010 掳, the maximum displacement is about 10 cm, the angle between the direction and the vertical direction is about 30 掳and 60 掳, the maximum displacement is about 15 cm. In the process of rainfall, the top of the slope first produces a through pull crack, and after the water is further infiltrated, there are local tiny vertical cracks in the slope body. 4) the digital equipment is used to record the overall change of the slope and the change of the slope surface shape, etc. Taking the 45 掳model test as an example, it can be seen that the slope erosion has experienced the process of "deep erosion and lateral erosion development on the slope between the sheet erosion and the gully", which formed a large erosion trench and collapsed in the gully bank in the late stage, and the slope surface showed an overall downward trend because of the erosion. Rainfall makes the soil saturation degree is higher at the toe of the slope. The small landslide develops from the bottom to the top, and the landslide position of the slope soil gradually moves upward, and finally a large scale slope collapse occurs.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU411;TU444

【参考文献】