水位波动条件下基坑周围地基土的孔压响应

发布时间：2018-05-22 07:46

本文选题：水位波动 + 深基坑　；参考：《浙江大学》2013年硕士论文

【摘要】：随着我国经济的发展以及城市化进程的加快,各地高层建筑、地下空间和设施正如火如荼地建设,基坑工程所面临的环境愈加复杂。近年来涌现了大量的临海、临江深基坑工程,与传统内陆远离开阔水域基坑工程不同的是,该类工程受波浪、潮汐等引起的水位波动影响显著,水位波动对深基坑工程性状的影响是随工程实践产生的一个新课题。而研究水位波动条件下基坑的变形、稳定和围护结构受力等变化,关键问题在于研究基坑周围地基土的孔压响应机制。本文首先提出了滨海浅层含水层地下水位波动和临海水位波动两种情况下的基坑渗流简化分析模型,利用PLAXIS软件,基于Biot固结理论,建立相应的有限元数值分析模型；分析了浅层含水层地下水位波动与水位在海床面以上波动两种条件下基坑及周围地基的水土压力响应,并讨论相关参数对基坑渗流性状的影响；依托于港珠澳大桥珠海拱北隧道明挖暗埋海域段基坑工程,分析了水位波动对重力式挡墙基坑稳定性的影响；最后根据渗流条件将基坑渗流场分区,利用Laplace、Fourier变换分别推导了含水层地下水位波动、水位在海床面以上波动时板式支护结构基坑,以及含水层地下水位波动时重力式挡墙基坑周围地基孔压响应的二维近似半解析解。得到以下主要结论： 1、由水位波动引起的基坑周围地基的相对超孔压波动幅值沿最短渗流路径不断衰减,浅层含水层地下水位波动情况下基坑周围孔压波动滞后现象明显； 2、浅层含水层地下水位波动情况下,综合系数θ(与土体固结系数、海床厚度、水位波动周期相关)越大,基坑周围地基的相对超孔压波动幅值越小,滞后相位越大；然而,当水位在海床面以上波动时,θ越大,基坑主动侧的相对超孔压波动幅值越大,滞后相位越大,基坑被动侧的相对超孔压波动幅值则越小,但滞后相位还是越大；稳态渗流(θ=0)时的相对孔压为水位波动条件下不同θ时相对超孔压波动幅值的极值； 3、传播系数β越大,即饱和系数Sr越低,基坑周围的波动孔压响应幅值越小,孔压波动滞后相位越大； 4、围护墙底至底部不透水边界距离L、基坑宽度、渗透系数各向异性对水位波动条件下基坑周围的孔压响应影响明显。
[Abstract]:With the development of economy and the acceleration of urbanization, high-rise buildings, underground space and facilities are being constructed in full swing, and the environment of foundation pit engineering is becoming more and more complex. In recent years, a large number of deep excavation projects near the sea have emerged. Unlike the traditional inland and open water excavation projects, these projects are significantly affected by water level fluctuations caused by waves, tides, etc. The influence of water level fluctuation on the engineering behavior of deep foundation pit is a new subject arising from engineering practice. The key problem of studying the deformation, stability and stress of the surrounding foundation pit under the condition of water level fluctuation lies in the study of the pore pressure response mechanism of the foundation soil around the foundation pit. In this paper, a simplified analysis model of foundation pit seepage under the condition of shallow aquifer groundwater level fluctuation and coastal water level fluctuation is put forward, and the corresponding finite element numerical analysis model is established by using PLAXIS software and based on Biot consolidation theory. The soil and water pressure responses of foundation pit and surrounding foundation are analyzed under the condition of groundwater level fluctuation in shallow aquifer and the fluctuation of water level above the seabed surface, and the influence of relevant parameters on the seepage behavior of foundation pit is discussed. The influence of water level fluctuation on the stability of gravity retaining wall foundation pit is analyzed based on the foundation pit engineering of Zhuhai Gongbei Tunnel of HongKong-Zhuhai-Macao Bridge, and the seepage field of foundation pit is divided according to the seepage condition, and the influence of water level fluctuation on the stability of gravity retaining wall foundation pit is analyzed. By means of Laplace Fourier transform, 2-D approximate semi-analytical solutions of the pore pressure response around the foundation pit of the gravity retaining wall and the aquifer groundwater level are derived, respectively, in which the groundwater level fluctuates above the seabed surface, the plate retaining structure foundation pit is subjected to the fluctuation of the water level above the seabed surface, and the pore pressure response around the foundation pit of the gravity retaining wall is obtained. The main conclusions are as follows: 1. The amplitude of the relative super-pore pressure fluctuation of the foundation pit caused by the water level fluctuation continuously attenuates along the shortest seepage path, and the lag phenomenon of the pore pressure fluctuation around the foundation pit is obvious under the condition of the shallow aquifer groundwater level fluctuation; 2. In the case of groundwater level fluctuation in shallow aquifer, the larger the comprehensive coefficient 胃 (relative to soil consolidation coefficient, seabed thickness, water level fluctuation period), the smaller the amplitude of the relative excess pore pressure fluctuation and the larger the lag phase of the foundation around the foundation pit. When the water level fluctuates above the seabed surface, the larger 胃, the larger the amplitude of the relative super-pore pressure fluctuation and the larger the lag phase of the active side of the foundation pit, and the smaller the amplitude of the relative super-pore pressure fluctuation of the passive side of the foundation pit, but the larger the lag phase. The relative pore pressure of steady flow (胃 ~ 0) is the extreme value of the fluctuation amplitude of relative excess pore pressure under the condition of water level fluctuation. 3. The larger the propagation coefficient 尾, the lower the saturation coefficient Sr, the smaller the response amplitude of the wave pore pressure around the foundation pit, and the larger the lag phase of the pore pressure fluctuation. 4. The impervious boundary distance from bottom to bottom, the width of foundation pit and the anisotropy of permeability coefficient have obvious influence on the response of pore pressure around the foundation pit under the condition of water level fluctuation.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU470

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