Free Seepage Research Articles

РАСЧЕТЫ УСТАНОВИВШЕЙСЯ СВОБОДНОЙ ФИЛЬТРАЦИИ ИЗ НЕОБЛИЦОВАННЫХ КАНАЛОВ

Purpose: to obtain calculated dependencies for determining free and banked seepage from irrigation canals. Materials and methods: during the research, methods of the theory of filtration from unlined and lined canals of irrigation and drainage systems were used. Results. Free seepage from the canals with steady flow shows significant water losses, reaching 30 % of discharge. As a result, the canal efficiency decreases, thus contributing to the flooding of the canal areas, the subsequent soil salinization, waterlogging and their gradual withdrawal from agriculture. Free steady seepage from canals will be observed in the absence of impermeable water-resistant depth layers or when the groundwater level occurs at a depth of more than 20–25 m from the earth's surface. In this regard, to determine the seepage discharge with free seepage, the calculated dependences of N. N. Pavlovsky, V. V. Vedernikov, A. N. Kostyakov, S. F. Averyanov and Yu. M. Kosichenko are recommended. In the case when banked-up seepage occurs during steady motion, the method of filtration resistance and the formulas of S. F. Averyanov, N. N. Verigin, A. Ya. Oleinik, taking into account the unsteady seepage process, with differential equation of unsteady flow motion of the Fourier type may be used. Conclusions. The solutions obtained of seepage problems under steady motion made it possible to find calculated dependencies and calculation methods for free and banked-up seepage from irrigation canals. A classification of seepage losses from irrigation canals for free flow conditions has been developed.

Numerical modelling of the effect of horizontal drains in centrifuge tests on soil-structure interaction in liquefiable soils

The research presented herein was carried out in the framework of the H2020 LIQUEFACT project ( http://www.LIQUEFACT.eu/ ). This paper presents the results of a set of numerical analyses performed to study the soil-structure interaction in presence of a liquefiable soil. In the first part of the paper, the attention was focused on the ability of some advanced soil constitutive models to simulate the centrifuge tests carried out within the project. Two finite element codes, Plaxis 2D and OpenSees, were used for the computations. The results were analysed in terms of accelerations, displacements and pore pressures build up. In the second part of the paper the effects of the introduction of horizontal drains, as mitigation techniques against liquefaction, were shown and discussed in terms of their ability in reducing pore pressure build-up and building settlement. All the numerical predictions confirmed the experimental evidence that horizontal drains are able to reduce the excess pore pressure during shaking and the structural settlement. The amount of reduction depends on the water boundary condition at surface: a free seepage surface generally allowed a larger mitigation than where the liquefiable layer was topped by clay.

Role of river stage in characterization of phreatic line

PurposeThe purpose of this study is to understand the basics of interactions of groundwater and surface water, which is needed for effective management of water resources.Design/methodology/approachThe experimental setup was framed using curved flume and the straight flume, which simulates the model of river and groundwater storage, respectively. The model set up further consists, downstream, central and upstream sections where 14 observation wells, which are arranged at a measured distance from the canal side.FindingsExit gradient is higher at downstream when the average head differences between canal and river are 31.9 cm and 35.7 cm. Free seepage height is more in the downstream wells than upstream and central wells. At the downstream section, there is a greater chance of instability of the riverbank.Research limitations/implicationsResults will be used for better planning of hydraulic structural design.Practical implicationsResults will help in storing the large water and better irrigation planning for the water acute states and locations.Originality/valueThe originality is own developed physical model and its own first type to understand the basic of interaction and effects.

Seepage analysis in body and foundation of Sang Siah Dam using the Seep/W

Abstract. One of the most important topics in designing of earth dams is determine the drainage rate in body and foundation of dam. The aim of this study is evaluating the seepage in body and foundation of Sang Siah dam, located in Kurdistan province of IRAN. Seepage analysis was done by SEEP/W software, from GEO STUDIO package. Three sections of Sang Siah dam were analyzed using SEEP/W software and the seepage rate was evaluated. Afterwards, the effects of cut off wall, clay blanket and concrete coverage were investigated with SEEP/W software. The free seepage line was analyzed by creating clay blanket, concrete coverage and cut off wall and it was revealed that clay blanket can be a good option in order to decreasing seepage of dam. Overall results showed that the seepage rate calculated using the software had 7-8% different with the actual measurements, due to differences in dam’s dimensions at various sections, anisotropic of soil, etc. The results were generally acceptable.

Steady free-surface flow in porous media: generalized Dupuit–Fawer equations

Steady free-surface flow in open channels may be analysed by the reduction of the two-dimensional (2D) potential flow problem to a quasi-2D potential flow approach by inclusion of streamline curvature and inclination effects following Fawer's theory. Flow of water in open channels and groundwater flow with a free surface can be characterized by potential functions and stream functions both obeying Laplace's 2D equation, provided there is isotropy and homogeneity. It is thus natural to expect the transfer of ideas from the open channel to the groundwater flow. A novel approximate model based on Fawer's theory for steady open channel flows with curved streamlines, coupled with Darcy's law, is proposed for groundwater flow with a free seepage surface. The seepage surface is described by a second-order differential equation which is applied to flow through both rectangular and trapezoidal dams, resulting in good agreement with the full 2D potential flow methods and test data.

A priori error analysis of the mortar finite element method for variational inequalities

AbstractThe mortar finite element method is a special domain decomposition method, which can handle the situation where meshes on different subdomains need not align across the interface. In this article, we will apply the mortar element method to general variational inequalities of free boundary type, such as free seepage flow, which may show different behaviors in different regions. We prove that if the solution of the original variational inequality belongs to H2(D), then the mortar element solution can achieve the same order error estimate as the conforming P1 finite element solution. Application of the mortar element method to a free surface seepage problem and an obstacle problem verifies not only its convergence property but also its great computational efficiency. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2008

Calculation of free seepage from watercourses with curvilinear profiles

A strict hydromechanical solution is given to the problem of free seepage from watercourses (rivers, canals, water bodies, industrial and agricultural ponds) for a family of smooth and complex curvilinear profiles with the use of conformal mappings and with the representation of the flow domain as the basis of the water-course profile in the Zhukovski complex domain. All necessary parameters of the flow are determined, including the outline of the curvilinear profile of the watercourse, depression curves and constant pressure lines (isobars), seepage flow, etc. For the particular case of a circular base of the watercourse profile, the results of obtained solution coincide with the known exact solutions derived by V.V. Vedernikov and N.N. Pavlovskii. Specific numerical examples of calculations for watercourses with different relative widths are given.

Convergence analysis of P1 finite element method for free boundary problems on non-overlapping subdomains

The paper applies a conforming P 1 finite element method to general variational inequalities derived from free boundary problems. The domain of the free boundary problem can be properly split into two non-overlapping subdomains where the free boundary is located in only one subdomain. The variational inequality is reduced to a partial differential equation in the subdomain which does not contain the free boundary but still keeps its original form in the other subdomain. Therefore, the original variational inequality can be discretized separately with P 1 finite element in different subdomains. A non-overlapping domain decomposition method is introduced to solve these two discretized sub-problems by P 1 finite element method iteratively while a Robin type boundary condition is utilized for the data transfer on the common boundary. We show that the sequence of such finite element solutions converges to the discretized solution of the original problem. Application to a free seepage problem verifies the theory.

Boundary integral in free seepage analysis : Martins, J B; da Veiga, E V Proc 5th Engineering Mechanics Division Speciality Conference, Wyoming, 1–3 Aug 1984V1, P230–233. Publ New York: ASCE, 1984

Boundary integral in free seepage analysis : Martins, J B; da Veiga, E V Proc 5th Engineering Mechanics Division Speciality Conference, Wyoming, 1–3 Aug 1984V1, P230–233. Publ New York: ASCE, 1984