共查询到19条相似文献,搜索用时 438 毫秒
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要实现饱和-非饱和土体的水-气二相流-固耦合作用的数值模拟,关键是如何实现渗流场与应力场的耦合,目前,松弛耦合方法不仅精度能够满足一般的工程要求,而且求解方法易于实现,是多相流-固耦合问题研究的主要方向。本研究根据松弛耦合原理,利用TOUGH2/EOS3来模拟水-气二相渗流过程;利用FLAC3D来模拟土体变形;基于水-气二相渗流过程与力学过程的相互影响,给出饱和度-密度、孔隙水压力和气压力-有效应力、体积应变-孔隙率、孔隙率-固有渗透率,以及孔隙率-毛细压力等状态变量之间的耦合关系式;利用C++控制TOUGH2、FLAC3D在流固耦合过程中的有序运行并利用耦合关系式传递相关状态变量,以实现对水-气二相流-固耦合作用的模拟。利用该模型对一现场压气试验进行模拟,通过模型计算值与实测值的对比,验证了模型的准确性和有效性。 相似文献
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非饱和砂土坡面降雨非正交入渗试验与数值模拟研究 总被引:1,自引:0,他引:1
传统降雨入渗分析仅以降雨强度在坡面上的正交分量作为边界条件,不符合实际降雨非正交入渗规律。为了研究非饱和砂土的非正交入渗规律性,采用自行研制的室内降雨试验装置对非饱和砂土坡面进行了一系列不同降雨强度、坡角和孔隙比的降雨入渗试验,并对应地进行了正交入渗条件下的数值模拟。测量了入渗率、出渗速率及砂土储水增量随时间变化的关系曲线,分析了雨强、坡角和孔隙比对试验结果的影响。试验结果显示各试验中均无坡面径流现象,与正交入渗边界理论差异显著。通过分析非饱和砂土在传统坡面降雨正交入渗边界条件下的入渗率、出渗速率及砂土储水增量等数值模拟结果与对应的降雨入渗试验结果的差异,证明按正交入渗边界理论计算得到的砂土坡面土体含水率、入渗能力及坡面边界条件转化的判别机制均与实际情况不符。 相似文献
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《岩石力学与工程学报》2016,(Z2)
依据多相渗流和非饱和土理论,提出在潜在滑坡区后缘进行充气形成非饱和区,截排斜坡后缘来水向潜在滑坡区入渗,以降低潜在滑坡区的地下水位,提高边坡稳定性。采用长边坡二维有限元数值模拟方法,研究充气过程中坡体非饱和区气–水两相流运动特征和地下水位变化规律,为充气截排水技术运用于实际工程提供理论指导。通过分析充气点下游边坡地下水位的变化规律,论证充气截排水方法具有可行性;基于充气过程中非饱和区的扩展过程分析,将充气截排水分为3个阶段,即充气点附近非饱和区形成与扩展阶段、充气形成的非饱和区局部越过地下水位线的不稳定两相流阶段和充气形成的非饱和区基本稳定的截排水工作阶段;发现了充气过程中非饱和区孔隙气压力、孔隙气流速度、孔隙水渗流速度和体积含水量会随时间发生波动性变化,且四者的变化具有良好的相关性,当孔隙气压力随时间增大时,孔隙气体流速也随时间增大,孔隙水渗流速度和体积含水量则随时间减小,反之亦然,此规律的形成主要是气-水的流动性差异和相互驱动作用的结果。 相似文献
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多孔介质微观大小孔隙的分布及其连通具有随机性,使得流体在实际孔隙中的流动与理想单孔隙中迥异,当多孔介质中的含水量循环变化时,毛细滞回和残留含气量效应极大地影响着多孔介质的渗流过程。基于对非饱和孔隙介质干湿过程的分析,提出能够考虑残留含气量影响的土水特征关系理论模型,随后建立一个新的渗流理论模型,该模型考虑残留含气量对流动过程的影响。在此基础上,建立相应的数值分析模型,并进行程序代码的实施。建立的模型能够用于模拟任意含水量变化条件下残留含气量对多孔介质中非饱和渗流过程的影响。通过数值模拟结果与实测数据的比较,证实残留含气量效应对非饱和孔隙介质中流体分布的重要影响。为更准确地预测多孔介质中的土水状态,在非饱和渗流分析中考虑残留含气量与毛细滞回效应十分必要。 相似文献
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R. Chesnaux 《Water and Environment Journal》2009,23(1):32-40
The aim of this paper is to show how standard hydrogeologic software, usually used to model contaminant transport in groundwater under unsaturated conditions, can also be used to model gas transport in unsaturated porous media. Physical processes involved in the interaction between the atmosphere and the unsaturated soils are considered: transport by diffusion through the air and the groundwater, exchange between the liquid and gas phases and consumption. These physical processes are incorporated into the governing equations of a groundwater numerical code; by considering air, contained in the unsaturated soil, as water in the seepage numerical model, the air effectively becomes fluid within the numerical code. Then, the investigated gas is defined as the contaminant in the transport model, which is transported by -the air for the modeller-, and -water for the numerical code-. The over-riding assumption is that the air profiles and, therefore, water profiles of volume contents remain constant. The approach is illustrated using two examples, which consider the transport of oxygen. The first deals with oxygen distribution through a laboratory-cell diffusion containing reactive mining tailings. The second deals with the oxygen fluxes through the vadose zone, between the atmosphere and an unconfined aquifer's water table. Both examples consider different cases of oxygen consumption. 相似文献
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多孔介质中两相流动过程的毛细滞回效应 总被引:1,自引:1,他引:0
含水量大小以及干湿循环变化历史对多孔介质渗流过程有着重要影响。基于多孔介质理论和毛细滞回内变量模型,建立能够考虑含水量变化历史影响的多孔介质两相流动模型,并利用开发的U-DYSAC2有限元程序进行相应的数值模拟。通过模拟结果与试验数据的比较,验证所建数值模型在模拟复杂条件下非饱和多孔介质渗流问题的可靠性与有效性。对干湿循环变化条件下土质边坡渗流过程进行数值分析,结果表明:毛细滞回效应对非饱和土渗流过程具有显著影响,非饱和土水力状态不仅取决于当前含水量或基质吸力大小,而且还与土体所经历的水力历史有关;特别地,如果利用主脱湿线来描述土水特征关系,那么土体中基质吸力的预测结果会偏高,从而使得传统边坡稳定性分析方法高估土体抗剪强度以及坡体安全系数。因此,在模拟非饱和多孔介质复杂渗流问题时必须要考虑毛细滞回效应。 相似文献
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在阐述压气法隧道施工原理的基础上,建立了水–气二相流模型来模拟压气法隧道施工过程中超压空气驱替隧道周围土体的孔隙水的水–气二相流过程。该模型同时考虑了土体中气相和水相的流动以及水相和气相相互作用的影响,比较符合水–气二相渗流过程的物理意义。通过工程算例,计算出不同施工进度下开挖面和隧道混凝土衬砌上的空气损失速率以及空气入流对隧道周围土体渗流场的影响,结果表明:在均质的地质条件下,开挖面上的漏气速率一般为常数,而衬砌上的漏气速率将随着隧道长度的增加而线性增大。最后,提出了利用水–气二相流模型进一步提高压气法隧道施工的漏气量的数值模拟精度,需要深入研究的两点意见。 相似文献
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为研究海塘的洪水渗透规律和渗透破坏机制,提出了可考虑土体渗透性随渗透破坏而变化的饱和非饱和/非稳定渗流分析模型,编制了相应的程序.选取实际海塘进行了洪水渗透过程的数值模拟,并将计算结果与现场监测试验结果进行了对比,表明所建立的分析模型和计算程序是正确的.工程实例分析结果表明,海塘洪水渗透过程是一个涉及土体渗透性变化的饱和非饱和/非稳定渗流过程,塘身浸润线变化经历4个阶段,海塘渗透破坏是大渗流比降下洪水长时间渗透所导致的.因此海塘的洪水渗透破坏涉及破坏区土体渗透性的变化以及饱和-非饱和/非稳定渗流,按中国现行规范应用稳定渗流分析方法进行计算是存在问题的. 相似文献
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Tomohiro Mori Ryosuke Uzuoka Takashi Chiba Kenji Kamiya Motoki Kazama 《Soils and Foundations》2011,51(6):1075-1090
This paper presents a case study on a numerical prediction of the seepage and seismic behaviors of an unsaturated fill slope. In this study, the numerical prediction is performed with a dynamic three-phase (soil, water and air) coupled analysis based on porous media theory and constitutive models. The weak forms of three governing equations, momentum balance equations of the overall three-phase material and mass and the momentum balance equations of the pore fluids (water and air), are implemented in a finite element model. The discretized equations are solved by the fully implicit method and the skeleton stress is also implicitly integrated. The in-situ observation at the target fill slope of the case study has been ongoing since 2006. First, distributions of water saturation in the fill slope are simulated by performing seepage analyses to reproduce the in-situ ground water level in the fill slope. Second, seismic responses of the fill slope during two past earthquakes are simulated, and the numerical method is validated by comparing observed acceleration records and numerical one. Finally, seismic responses of the fill slope during a future scenario earthquake are predicted under different moisture conditions of unsaturated fill. As a result, the following findings were obtained. 1) The shape of the ground water level was partially reproduced from the quite dry fill slope element by using virtual constant precipitation. However, the observation results of moisture distribution above the ground water level were not reproduced. 2) In the validation analyses after two earthquakes, the numerical method reproduced the positions of peak frequency of acceleration Fourier spectra. 3) The numerical results clearly showed that frequency characteristics of the seismic response and the residual displacement of the fill slope were affected by the initial distribution of the degree of saturation in the fill ground. 相似文献
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张玉军 《岩石力学与工程学报》2005,(17)
从建立应力平衡方程、水连续性方程和弹塑性矩阵入手,使用Galerkin方法,将各控制方程分别在空间域和时间域进行离散,初步开发出了一个用于分析饱和–非饱和孔隙介质中水–应力耦合弹塑性问题的二维有限元程序。通过引入一组特定的与非饱和状态有关的计算公式,对一个假定的非饱和土体中水–应力耦合问题进行了数值计算,考察了不同时间土体中的位移、孔隙水压力、有效主应力、流速和塑性区的分布,定性验证了该程序的正确性。 相似文献
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Fusao Oka Sayuri Kimoto Naoaki Takada Hitoshi Gotoh Yosuke Higo 《Soils and Foundations》2010,50(4):483-494
A multiphase deformation analysis of a river embankment was carried out using an air-soil-water coupled finite element method capable of considering unsaturated seepage flow. A numerical model for unsaturated soil was constructed based on the mixture theory and an elasto-viscoplastic constitutive model. The theory used in the analysis is a generalization of Biot's two-phase mixture theory for saturated soil. An air-soil-water coupled finite element method was developed using the governing equations for three-phase soil based on the nonlinear finite deformation theory, i.e., the updated Lagrangian method. Two-dimensional numerical analyses of the river embankment under seepage conditions were conducted, and the deformation associated with the seepage flow was studied. We have found that the occurrence of large deformations corresponds to the large values of the hydraulic gradients at the toe of the embankment, and that the overflow of river water makes the embankment more unstable. It has been confirmed that seepage-deformation coupled three-phase behavior can be simulated well with the proposed method. 相似文献
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Compacted soils are widely used in engineering work and engineers often specify that cohesive soils be compacted either around or on the wet side of optimum water content. In general, at the corresponding degree of saturation values, water component in soil voids is continuous but the air phase is not. The modelling of the infiltration process through compacted soils requires that unsaturated hydraulic functions be defined. A theoretical soil water retention function for soils with a discontinuous air phase is derived using the theory proposed by Schuurman (1966). Data from the test results provide encouraging evidence of the validity of the proposed theory. An empirical hydraulic conductivity function where the air is present in the form of occluded bubbles is also determined by curve fitting to the experimental measurements. A numerical solution of Richards' equation for one-dimensional flow, which incorporates the experimental findings, was used to simulate the measured transient water flow. The results show that the proposed constitutive relationships are capable of producing simulations of the measurements of the unsaturated flow that are both qualitatively and quantitatively realistic. 相似文献