排水对非饱和残积土坡复杂渗流场调控机理研究

发布时间：2018-03-01 15:28

本文关键词： PLAXIS 排水孔布设有限元模拟复杂渗流场花岗岩残积土　出处：《福州大学》2014年硕士论文　论文类型：学位论文

【摘要】：渗流控制是改善边坡渗流场的有效途径,工程上广泛应用排水系统对边坡渗流场进行调控,以达到疏干地下水,增强抗剪强度,实现边坡抗滑的目的。含排水孔的渗流场十分复杂,涉及到排水、大气降雨、地下水等非饱和-饱和渗流的共同作用,受到降雨强度与模式、边坡土性与结构、排水系统布设等多因素的共同影响与制约。由于没有阐明多因素影响下排水对边坡渗流场的调控作用,揭示排水调控机理及确定主控因素,目前的布设方案主要停留在依靠经验和规范的水平,理论研究远落后于工程实际,带来诸多问题,如排水孔失效、过密、无法达到排水要求等。因此,开展排水对非饱和残积土坡复杂渗流场调控机理研究,对科学有效地指导相关工程具有重要的理论意义和工程实用价值。本文利用PLAXIS有限元软件中的PLAXFLOW模块进行二维渗流分析,土体模型采用Van Genuchten非饱和土模型,排水孔采用空气单元法结合材料单元配合幕工具进行模拟。首先,以福建省典型花岗岩残积土均质土坡为研究对象,进行非饱和残积土坡排水与不排水两种条件下的对比模拟,研究不同降雨条件、地下水位以及是否布设排水孔条件下边坡渗流场的调控规律。未布设排水孔时坡脚最容易发生破坏,长时间持续的强降雨对边坡稳定影响最大,随着边坡土质细颗粒增多,降雨入渗速度变缓、饱和度增高；布设排水孔之后可以排出一部分入渗的雨水、显著降低地下水位,坡体各点的饱和度和渗流流速都有明显降低,对边坡渗流场的调控具有积极作用。其次,以福建省典型花岗岩残积土多层土坡为研究对象,分析对比了在边坡排水孔选型和布设时孔径、孔长、倾角对其排水效果的影响,同时验证了沿高程方向布设多排排水孔时的排水效果。在工程常用取值范围内,排水孔孔长对排水效果影响较大,排水孔布设长度应根据边坡需要治理的范围来确定；排水孔孔径影响较小,提出了孔径选择建议；倾角对排水孔调控范围有影响,可根据需要降低的地下水位进行选择。当在边坡高程方向布设多排排水孔后,对地下水位有明显的调控作用,表现在地下水浸润线变缓,水位降低,各参考点流速变慢。最后,对一工程实例采用了最优排水孔布设,验证了排水孔可以有效排出坡体内的水,提高坡体的稳定性,并建议结合其他加固措施确保边坡的稳定。
[Abstract]:Seepage control is an effective way to improve the seepage field of the slope. The drainage system is widely used in engineering to regulate the seepage field of the slope in order to drain the groundwater and enhance the shear strength. The seepage field with drainage holes is very complex, which involves the joint action of unsaturated and saturated seepage such as drainage, atmospheric rainfall, groundwater and so on, and is subjected to rainfall intensity and model, slope soil property and structure, etc. The influence and restriction of many factors, such as the layout of drainage system, has not been clarified, and the regulating effect of drainage on seepage field of slope has not been clarified, and the mechanism of drainage regulation and the determination of main controlling factors have been revealed. At present, the layout scheme mainly stays at the level of relying on experience and norms, and the theoretical research falls far behind the engineering practice, which brings many problems, such as the failure of drainage holes, too tight, unable to meet the drainage requirements and so on. It is of great theoretical significance and practical value to study the regulation mechanism of drainage on the complex seepage field of unsaturated residual slope, which is of great theoretical significance and practical value to guide the relevant engineering scientifically and effectively. In this paper, the two-dimensional seepage analysis is carried out by using the PLAXFLOW module in the PLAXIS finite element software. The soil model is Van Genuchten unsaturated soil model, and the drainage hole is simulated by air element method combined with material element fitting curtain tool. Firstly, the typical granite residual soil homogeneous slope in Fujian Province is taken as the research object. The comparison and simulation of unsaturated residual soil slope drainage and undrainage are carried out to study different rainfall conditions. Under the condition of underground water level and whether or not the drainage hole is installed, the seepage field of the slope is regulated. When the drainage hole is not installed, the foot of the slope is most likely to be destroyed, and the long lasting heavy rainfall has the greatest influence on the stability of the slope, and with the increase of fine soil particles of the slope, The rainfall infiltration rate becomes slower and the saturation increases. Rain Water, who can discharge part of the infiltration after the drainage hole is laid out, significantly reduces the underground water level, and the saturation and seepage velocity at all points of the slope body are obviously reduced. Secondly, taking the multi-layer soil slope of typical granite residual soil in Fujian Province as the research object, the influence of pore diameter, hole length and inclination angle on drainage effect of slope drainage hole selection and layout is analyzed and compared. At the same time, the drainage effect is verified when multiple drainage holes are arranged along the elevation direction. In the range of commonly used values in engineering, the length of drainage holes has a great influence on the drainage effect, and the length of drainage hole layout should be determined according to the scope of slope treatment. The influence of pore diameter on the drainage hole is small, the selection of pore diameter is suggested, and the inclination angle has an effect on the range of drainage hole regulation, which can be selected according to the need to reduce the groundwater level. When multiple drainage holes are arranged in the direction of slope elevation, It has obvious regulating effect on groundwater level, which is shown by the decrease of groundwater level, the decrease of groundwater level and the decrease of flow velocity of each reference point. Finally, the optimal drainage hole layout is adopted for an engineering example. It is proved that the drainage hole can effectively discharge the water from the slope body and improve the stability of the slope body, and it is suggested that the stability of the slope can be ensured by combining other reinforcement measures.
【学位授予单位】：福州大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU463

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