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黄土坡体滑坡水土耦合机理及其应用研究
Alternative TitleSeepage-stress Coupling Mechanism and Application in Loess Slope Landslide
周丹洋
Thesis Advisor李家春
2019-05-28
Degree Grantor中国科学院大学
Place of Conferral北京
Subtype硕士
Degree Discipline流体力学
Keyword黄土,渗流稳定性,降雨,灌溉,排水
Abstract

我国黄土分布广泛,尤其是在黄河中游的甘肃、宁夏、陕西、山西等黄土高原地区,是世界上水土流失最严重和生态环境最脆弱的地区之一。在持续降雨或突降暴雨或大面积灌溉的情况下,滑坡灾害频繁发生,致灾严重,对当地人民的生命财产安全造成极大的威胁。本文研究黄土坡体滑坡灾害形成、发生、发展的规律与水土耦合机理,旨在为该地区滑坡灾害的防治提供科学依据。

本文首先建立了渗流条件下坡体稳定性分析模型,采用有限元强度折减法对杨家岭滑坡进行了数值模拟,并与传统方法的计算结果进行了对比,验证了本模型的可靠性。以20177月下旬我国陕西榆林地区突降暴雨诱发的严重滑坡灾害为案例, 分析了不同降水历程以及考虑水对土体弱化作用后坡体稳定性的变化。再以1969年甘肃省黑方台地区的提灌工程为背景,进行10年灌溉期的数值模拟,分析了最佳排水孔长度的设置。并针对当地作物对科学灌溉方法进行初步探讨。论文研究的主要研究结果如下:

针对陕西榆林滑坡案例,分析了不同降水强度和持续时间对于黄土坡体稳定性的影响。研究发现黄土土坡上的降水会快速入渗,导致孔隙水压骤增,坡体稳定性降低。安全系数下降速度由快变慢,这是由于黄土结构沟豁纵横,裂隙丰富所致。模拟结果还表明,土体的初始含水量越大,坡体的稳定性越低,也愈容易发生滑坡灾害。

大量实验证明,土体含水可降低土体抗剪强度(包括粘聚力和摩擦角),所以,水土耦合必须考虑水对土体强度的弱化作用。我们发现土体强度的减弱会直接导致坡体稳定性的进一步下降,相比土体内摩擦角,土体的粘聚力降低的作用更加明显。

对黑方台地区长年大水漫灌条件下坡体内部渗流进行模拟,发现在灌溉水达到地下水位前,坡体处于较稳定的状态;当入渗锋面到达地下水位后,坡体内的灌溉水对地下水位进行补给,使地下水位快速抬升,从而降低坡体稳定性,极易导致滑坡灾害的发生。

为防治因灌溉引起的黄土坡体滑坡,利用排水方法即可取得明显效果,经济实用。针对实际的工程案例,排水孔的长度设置在一个最佳值时效果最好。同时,我们还根据当地生态环境和农作物需求,进行科学灌溉的模拟,从而达到防治滑坡和节约用水的目的。

Other Abstract

Loess in China is widely distributed, especially in the Loess Plateau such as Gansu, Ningxia, Shaanxi, and Shanxi in the middle reaches of the Yellow River. It is one of the regions with the most serious soil erosion and the most ecological environment in the world. In the case of continuous rainfall or sudden downpour or large-scale irrigation, landslide disasters occur frequently, causing serious disasters, posing a great threat to the lives and property of local people. This paper studies the formation, occurrence and development of the landslide hazard of the loess slope and the coupling mechanism of water and soil, aiming to provide a scientific basis for the prevention and control of landslide disasters in this area.

In this paper, the slope stability analysis model under seepage condition is established firstly. The Yangjialing landslide is numerically simulated by finite element strength reduction method, and compared with the traditional method, the reliability of the model is verified. Taking the severe landslide caused by sudden rainstorm in Yulin, Shaanxi Province in late July 2017 as an example, the variation of different rainfall processes and the stability of slope after considering the weakening effect of water on soil were analyzed. Based on the irrigation project in Heifangtai area of ​​Gansu Province in 1969, the numerical simulation of the 10-year irrigation period was carried out, and the optimal drainage hole length setting was analyzed. A preliminary discussion on scientific irrigation methods for local crops. The main findings of the thesis research are as follows:

According to the case of Yulin landslide in Shaanxi, the effects of different rainfall intensity and duration on the stability of loess slope are analyzed. It is found that the rain on the loess soil slope will infiltrate rapidly, resulting in a sudden increase in pore water pressure and a decrease in slope stability. The rate of decline of the safety factor is slower and slower. This is due to the fact that the loess structure is thick and vertical, and the crack is rich. The simulation results also show that the greater the initial water content of the soil, the lower the stability of the slope, and the more likely the landslide disaster occurs.

A large number of experiments have proved that the soil water content can reduce the soil shear strength (including cohesion and friction angle), so the water and soil coupling must consider the weakening effect of water on the soil strength. We have found that the weakening of the soil strength directly leads to a further decline in the stability of the slope. The effect of the soil's cohesion is more obvious than the soil friction angle.

The simulation of the seepage inside the slope under the condition of flood irrigation in the Heifangtai area shows that the slope is in a stable state before the irrigation water reaches the groundwater level. When the infiltration front reaches the groundwater level, the irrigation water in the slope body replenishing the groundwater level will cause the groundwater level to rise rapidly, thus reducing the stability of the slope and easily causing landslide disasters.

In order to prevent loess landslide caused by irrigation, the drainage method can be used to obtain obvious effects, which is economical and practical. For practical engineering cases, the length of the drain hole is best at setting an optimum value. At the same time, we also carry out scientific irrigation simulation according to the local ecological environment and crop demand, so as to achieve the purpose of preventing landslides and saving water.

Language中文
Document Type学位论文
Identifierhttp://dspace.imech.ac.cn/handle/311007/79112
Collection流固耦合系统力学重点实验室
Recommended Citation
GB/T 7714
周丹洋. 黄土坡体滑坡水土耦合机理及其应用研究[D]. 北京. 中国科学院大学,2019.
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