共查询到20条相似文献，搜索用时 718 毫秒
1.
岩体裂隙网络非稳定渗流分析与数值模拟 总被引：1，自引：0，他引：1
针对裂隙岩体的非稳定渗流问题,通过将Darcy定理扩展到包含干区的整个裂隙网络区域,并令潜在溢出边界条件为Signorini型互补边界条件,将湿区上的非稳定渗流问题转化为全域上的一个新的初边值问题。为降低试探函数选取的难度,建立与定义在整个裂隙网络区域上的偏微分方程（PDE）提法等价的抛物型变分不等式（PVI）提法,并给出裂隙网络非稳定渗流分析的有限元数值分析格式和迭代算法,与砂槽模型试验数据的对比分析,验证其有效性。最后,将文中发展的计算方法应用到含复杂裂隙网络的边坡非稳定渗流分析,计算结果很好地反映出边坡内部自由面随库水降落的变化规律,并能准确地描述裂隙网络内部渗流运动特征及流量分布的不均匀性。 相似文献
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This paper proposed a numerical formulation for unsaturated flow problems with nonlinear boundaries of seepage face and soil–atmosphere interface via the concept of parabolic variational inequality (PVI) method. A unified unilateral boundary condition was first proposed to represent the conditions on the seepage face and soil–atmosphere interface boundaries within the partial differential equation (PDE) formulation. A PVI formulation mathematically equivalent to the PDE formulation was then proposed, which automatically transforms the flux part of the unified unilateral boundary condition into the natural boundary condition and eliminates the singularity at seepage points. By discretizing the PVI formulation, a finite element procedure together with an iterative algorithm was suggested. An existing experiment of unsaturated flow in a layered hillside and a laboratory test of unsaturated flow through sand flume performed in this study were used to validate the proposed method, with a good agreement between the measured and computed results and a satisfactory balance of mass being maintained during the simulations. The numerical results also indicated that the problem of mesh dependence associated with unsaturated flow simulations is well addressed with the proposed numerical method. Finally, the process of unsaturated flow in a soil slope with layers of horizontal drains subjected to rainfall/evaporation was further examined. The numerical results reveal that the deployment of drains in a soil slope can significantly lower the pore water pressure around the drains, with the bottom layer drains being most effective in controlling the seepage flow. 相似文献
3.
排水是岩土体及工程构筑物渗流控制的主要措施之一,其实质是通过在渗流域内形成潜在溢出边界或低水位边界而实现渗流控制的。在排水渗控条件下,渗流场往往具有强烈的边界非线性特征,Signorini型变分不等式方法从理论上为稳定和非稳定排水渗流问题提供了有效的分析方法,但其实际效果还需要得到试验的验证。通过开展含5个排水廊道的排水砂槽模型试验,研究了复杂排水条件下砂土渗流的基本规律,并通过试验数据与数值计算成果的对比分析,论证了Signorini型变分不等式方法的有效性和正确性。试验结果表明,在稳定渗流条件下,排水砂槽上游侧3个排水廊道对渗流控制起主导作用,而下游侧2个廊道则失去排水功能,数值计算与试验成果吻合较好;在非稳定渗流条件下,受测压管精度、砂样均匀性和毛细效应的影响,数值计算与试验成果存在一定偏差,但也较好地揭示了复杂排水条件下砂槽中的非稳定渗流特征。排水砂槽试验结果验证了Signorini型变分不等式方法的有效性和正确性,为复杂排水条件下岩土体及工程构筑物的渗控结构优化设计提供了有效的分析手段。 相似文献
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软土在低水力坡降下的渗流会偏离达西定律,即为非达西渗流模式。假设孔隙水渗透服从指数渗流模式,采用镜像法原理推导了浅埋单孔和双孔圆形隧道非达西渗流场的解析解。结合算例,对浅埋圆形隧道非达西渗流解析解与达西渗流解析解进行了对比分析与验证,并对非达西渗流指数、隧道周围土体与衬砌渗流系数比值对隧道渗流场的影响进行了讨论。结果表明：非达西渗流指数、渗流系数比值对隧道渗流量和周围土体孔压均有较大的影响;随着渗流指数逐渐增大,土体内水头损失加快,隧道周围土体孔压及渗流量逐渐减小;随着土体与衬砌渗流系数比值逐渐增大,衬砌排水能力增强,隧道渗流量逐渐增大,隧道周围土体孔压减小更大。 相似文献
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In this study, a simplified analytical closed‐form solution, considering plane strain and axial symmetry conditions, for analysis of a circular pressure tunnel excavated underwater table, is developed. The method accounts for the seepage forces with the steady‐state flow and is based on the generalized effective stress law. To examine the effect of pore pressure variations and also the boundary conditions at the ground surface, the formulations are derived for different directions around the tunnel. The proposed method can be applied for analysis and design of pressure tunnels. Illustrative examples are given to demonstrate the performance of the proposed solution and also to examine the effect of seepage forces on the stability of tunnels. The simplified analytical solution derived in this study is compared with numerical analyses. It is concluded that the classic solutions (Lame's thick‐walled solution), considering the internal pressure as a mechanical load applied to the tunnel surface, are not applicable to pervious media and can result in an unsafe design. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
7.
Transient seepage analysis in zoned anisotropic soils based on the scaled boundary finite‐element method 
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下载免费PDF全文 The scaled boundary finite‐element method, a semi‐analytical computational scheme primarily developed for dynamic stiffness of unbounded domains, is applied to the analysis of unsteady seepage flow problems. This method is based on the finite‐element technology and gains the advantages of the boundary element method as well. Only boundary of the domain is discretized, no fundamental solution is required and singularity problems can be modeled rigorously. Anisotropic and non‐homogeneous materials satisfying similarity are modeled with no additional efforts. In this study, firstly, formulation of the method for the transient seepage flow problems is derived followed by its solution procedures. The accuracy, simplicity and applicability of the method are demonstrated via four numerical examples of transient seepage flow – three of them are available in the literature. Homogenous, non‐homogenous, isotropic and anisotropic material properties are considered to show the versatility of the technique. Excellent agreement with the finite‐element method is observed. The method out‐performs the finite‐element method in modeling singularity points. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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根据水位条件、施工工艺和防排水设计原则将隧道渗流计算围岩透水边界条件大致划分为4种类型,并分析了不同透水边界条件适应的施工工况。基于复变函数理论和保角映射方法,推导得出4种透水边界条件下隧道围岩内任一点孔隙水压力和隧道涌水量解析计算公式,通过与数值解的对比,印证了解析解的准确性。在此基础上,根据不同透水边界条件下隧道涌水量和围岩关键点孔隙水压力随埋深直径比（ ）的变化规律,分析了透水边界条件的变化对浅埋隧道和深埋隧道的影响,并探讨了浅埋水下隧道渗流计算中透水边界条件的选取。相关结论与认识对于隧道渗流计算和排水设计具有一定的指导作用和参考价值。 相似文献
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Darcian flow under/through a leaky cutoff wall: Terzaghi–Anderson's seepage problem revisited 下载免费PDF全文
下载免费PDF全文 An analytical solution is obtained for 2‐D steady Darcian flow under and through a cutoff wall partially obstructing a homogeneous isotropic foundation of a dam. The wall is leaky; that is, flow across it depends on the ratio of hydraulic conductivity of the wall and the wall thickness that results in the third‐type (Robin) boundary condition along the wall, as compared with the Terzaghi problem for an impermeable wall. The Laplace equation for the hydraulic head is meshlessly solved in a non‐standard flow tube. A Fredholm equation of the second kind is obtained for the intensity of leakage across the wall. The equation is tackled numerically, by adjusted successive iterations. Flow characteristics (total Darcian discharge and its components through the wall and the window between the wall top and horizontal bedrock, stream function, head distribution, and Darcian velocity along the wall and tailwater bed) are obtained for various conductivity ratios, head drops across the structure, thicknesses of the foundation, and the degree of its blockage by the wall. Comparisons with the Terzaghi limit of an impermeable wall show that for common wall materials and thicknesses, the leakage may constitute tens of percent of the discharge under the dam. The through‐flow hydraulic gradients on a vertical wall face (Robin's boundary condition) as well as the exit gradients along a horizontal tailwater boundary (Dirichlet's boundary condition) acting for decades have deleterious impacts on dam stability because of potential heaving, piping, and mechanical–chemical suffusion. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
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卡拉水电站坝区渗流控制效应精细模拟与评价 总被引：1，自引：0，他引：1
卡拉水电站坝址区河谷狭窄,岸坡陡峻,地质条件复杂,渗漏问题突出。为减小卡拉坝区渗漏并改善大坝的渗透稳定性,工程设计采取防渗帷幕、排水孔幕和排水洞等防渗排水措施。采用子结构、变分不等式和自适应罚函数相结合的方法（简称SVA方法）,结合典型溢流坝段与坝区整体渗流场分析成果,评价卡拉大坝及坝基渗流控制方案的合理性,并论证其优化的可能性。研究表明：①防渗帷幕有效雍高了帷幕上游侧岩体内的地下水位、增加了绕坝渗流的渗径长度并降低了坝基的扬压力,排水系统则显著降低了坝体内的孔隙水压力以及坝基扬压力;②排水孔幕间距对坝体内的自由面分布有着显著影响,排水孔幕间距取3.0～4.5 m是合适的。 相似文献
11.
Farhang Daneshmand 《国际地质力学数值与分析法杂志》2012,36(6):780-797
One major difficulty in seepage analyses is finding the position of phreatic surface which is unknown at the beginning of solution and must be determined in an iterative process. The objective of the present study is to develop a novel non‐boundary‐fitted mesh finite‐element method capable of solving the unconfined seepage problem in domains with arbitrary geometry and continuously varied permeability. A new non‐boundary‐fitted finite element method named as smoothed fixed grid finite element method (SFGFEM) is used to simplify the solution of variable domain problem of unconfined seepage. The gradient smoothing technique, in which the area integrals are transformed into the line integrals around edges of smoothing cells, is used to obtain the element matrices. The solution process starts with an initial guess for the unknown boundary and SFGFEM is used to approximate the field variable. The boundary shape is then modified to eventually satisfy nonlinear boundary condition in an iterative process. Some numerical examples are solved to evaluate the applicability of the proposed method and the results are compared with those available in the literature. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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A new artificial boundary approach for transient seepage problems in unbounded domain is presented. The artificial boundary condition at the truncated boundary is derived from the analytical solutions for transient seepage problems in one dimension, including solutions, respectively, for flow in one‐dimensional infinite space and for radial flow in an infinite layer, and then it is tentatively applied for some two dimensional problems in addition to the one‐dimensional problems mentioned above. The boundary conditions derived relate the time‐dependent boundary flux with the time derivative of the hydraulic head at the truncated boundary, which makes the implementation much easier compared with the infinite element method. The accuracy and efficiency of the artificial boundary are validated by several numerical examples, which shows that the proposed boundary can give very good results for one‐dimensional transient seepage problems, as expected, whereas reasonable results can be also obtained for two‐dimensional problems, such as two‐dimensional axisymmetric flow and flow in an infinite plane. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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A local artificial boundary for transient seepage problems with unsteady boundary conditions in unbounded domains 下载免费PDF全文
下载免费PDF全文 Numerical analysis of transient seepage in unbounded domains with unsteady boundary conditions requires a more sophisticated artificial boundary approach to deal with the infinite character of the domain. To that end, a local artificial boundary is established by simplifying a global artificial boundary. The global artificial boundary conditions (ABCs) at the truncated boundary are derived from analytical solutions for one‐dimensional axisymmetric diffusion problems. By applying Laplace transforms and introducing some specially defined auxiliary variables, the global ABCs are simplified to local ABCs to significantly enhance the computational efficiency. The proposed local ABCs are implemented in a finite element computer program so that the solutions to various seepage problems can be calculated. The proposed approach is first verified by the computation of a one‐dimensional radial flow problem and then tentatively applied to more general two‐dimensional cylindrical problems and planar problems. The solutions obtained using the local ABCs are compared with those obtained using a large element mesh and using a previously proposed local boundary. This comparison demonstrates the satisfactory performance and obvious superiority of the newly established boundary to the other local boundary. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
14.
对滑坡防治工程相关规范中渗流问题的研究 总被引：1，自引：0，他引：1
渗流对滑坡稳定性至关重要,在松散堆积层滑坡稳定性评价中如何正确反映渗透力的作用是岩土工程界近年来讨论的热点。目前涉及滑坡防治工程的有关国家规范已经考虑渗流的影响,但在渗透力的重复计算上存在突出的问题,一些重要的概念和原理亟待从源头上进行澄清。文中以流体力学的基本理论为依据,从渗透力概念定义的微观源头上,证明了渗透力是一种等效力。在非压缩流体条件下,无论稳定流还是非稳定渗流,渗透力与浮力的共同作用效果与周边孔隙水压力是完全等效的。针对滑坡渗流模型,从宏观上再次证明了上述等效性原理,且表明在流网比较简单的条件下,采用渗透力计算比较简便,论证了更为严格的条件下条分法的下滑力中应考虑渗透力和浮力的影响。在此基础上,对现有规范的稳定性评价和滑坡推力计算方法进行了修正,定性和定量地评价了现行规范评价方法的偏差对滑坡设计推力和工程造价影响的程度。实际算例表明,现行规范的设计推力偏大5 %以内,主体工程造价偏大幅度基本与此相当,并略低。 相似文献
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A practical and efficient numerical scheme for the analysis of steady state unconfined seepage flows
The scaled boundary finite‐element method (SBFEM), a novel semi‐analytical technique, is applied to the analysis of the confined and unconfined seepage flow. This method combines the advantages of the finite‐element method and the boundary element method. In this method, only the boundary of the domain is discretized; no fundamental solution is required, and singularity problems can be modeled rigorously. Anisotropic and nonhomogeneous materials satisfying similarity are modeled without additional efforts. In this paper, SBFE equations and solution procedures for the analysis of seepage flow are outlined. The accuracy of the proposed method in modeling singularity problems is demonstrated by analyzing seepage flow under a concrete dam with a cutoff at heel. As only the boundary is discretized, the variable mesh technique is advisable for modeling unconfined seepage analyses. The accuracy, effectiveness, and efficiency of the method are demonstrated by modeling several unconfined seepage flow problems. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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关于渗流的力及其应用 总被引：5，自引：1，他引：4
饱和渗流是岩土体失稳的重要因素。叙述了渗流产生的消极破坏力“浮力”和积极破坏力“渗透力”。较详细地讨论了渗流各力之间的相互转换关系及其在管涌滑坡问题中的正确应用;并特别推荐引用渗透力计算滑坡问题具有简便、精确的优点。并指出了在计算中和设计规范中引用渗流力方面的误解。 相似文献
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通常的渗流计算中排水的模拟方法很多,诸如排水子结构法、增加渗透阻抗等。但大型地下厂房与洞室的排水非常复杂,若对每个排水孔都进行模拟就非常繁杂。利用简化方法,采用给定水头和给定流量相结合的方法可以较为方便地解决复杂排水模拟的问题。对糯扎渡地下厂房和洞室群的复杂排水和对左岸包括地下厂房与硐室进行渗流计算分析,通过多个计算方案的比较,对给定流量和给定水头模拟排水效果进行合理假定,使模拟结果得到的排水区流量和水头趋于一致,由此得到合理可靠的排水模拟效果。对模拟得到的糯扎渡左岸山体渗流场进行了分析。计算结果有助于优化工程渗控方案,同时为计算变形稳定提供合理可靠的水荷载。 相似文献
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A major challenge in seepage analysis is to locate the phreatic surface in an unconfined aquifer. The phreatic surface is unknown and assumed as a discontinuity separating the seepage domain into dry and wet parts, thus should be determined iteratively with special schemes. In this study, we systematically developed a new numerical manifold method (NMM) model for unconfined seepage analysis. The NMM is a general numerical method for modeling continuous and discontinuous deformation in a unified mathematical form. The novelty of our NMM model is rooted in the NMM two‐cover‐mesh system: the mathematical covers are fixed and the physical covers are adjusted with iterations to account for the discontinuity feature of the phreatic surface. We developed an energy‐work seepage model, which accommodates flexible approaches for boundary conditions and provides a form consistent with that in mechanical analysis with clarified physical meaning of the potential energy. In the framework of this energy‐work seepage model, we proposed a physical concept model (a pipe model) for constructing the penalty function used in the penalty method to uniformly deal with Dirichlet, Neumann, and material boundaries. The new NMM model was applied to study four example problems of unconfined seepage with varying geometric shape, boundary conditions, and material domains. The comparison of our simulation results to those of existing numerical models for these examples indicates that our NMM model can achieve a high accuracy and faster convergence speed with relatively coarse meshes. This NMM seepage model will be a key component of our future coupled hydro‐mechanical NMM model. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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半无限含水层中带衬砌隧洞渗流解析研究 总被引：3，自引：0，他引：3
现有关于半无限含水层中隧洞渗流的解析解不能考虑衬砌部分排水的特性。假定土体和衬砌均为饱和均匀连续介质,采用土体与衬砌分算;利用复变函数解决孔口问题基本方法,对土体采用共形映射坐标变换,将土体中的渗流方程转换为与衬砌部分类似的二维Laplace方程圆环域的Dirichlet问题;通过Fourier解法,根据边界条件并利用流量连续条件,求得半无限空间中带衬砌隧洞渗流量和衬砌周边水头解析解答。分析了径深比、土体与衬砌渗透系数相对值、内壁水压力等因素对渗流量和衬砌周边水头的影响,并与数值算例进行了比较。结果表明,对浅埋隧洞该解析解仍具有较好的精度,是简便、实用的计算方法。 相似文献