The resulting values of head will be used to derive equipotentials which will be compared to those obtained using a flow net sketch. Soil mechanics note 5 flow net construction and use. How to draw flow net seepage by hand soil mechanics. Seepw can model simple saturated steadystate problems or sophisticated saturated unsaturated transient analyses with atmospheric coupling at the ground surface. Flow lines represent the path of flow along which the water will seep through. Properties and application of flow net are explained in this article.
One of the reasons for presenting this case is that it appears in most text books on seepage and consequently. Procedures for confined flow, unconfined flow, and multilayer systems are presented with examples. Seepage, drainage, and flow nets, third edition, features. Seepw is a powerful finite element software product for modeling groundwater flow in porous media. From such maps, flow directions, rates of flow, and the hydrostratigraphy can often be inferred. Use this procedure to estimate seepage quantity and distribution of pore water pressures in.
This lecture talks about flow nets and how to draw them by hand. The resulting solutions have been used to prepare graphical design aids that con be readily applied by the highway designer. From the drawn flow net, n f and n d can be easily counted, and hence, the seepage discharge can be easily computed by using eqn. Seepage, drainage, and flow nets is the definitive reference on seepage and drainage through soils for engineering purposes. Groundwater flow nets graphical solutions to the flow. Flow rate per meter length of sheet pile, if k 1104 msec 2. Seepage % hydraulic structures % net flow % finite elements % karkheh dam introduction water leakage at earth dams and its method f o in eyes of engineers, dams are known as alive dams 6, 7. Completewith solid coverage of seepage principles and flow netconstruction, this book is an invaluable aid to. Water seepage model in ideal cracks straight and smooth as the fig. Flow net and seepage analysis gate problems soil mechanics. Unconfined groundwater flow nets on a slope ce 215 soil mechanics 14. Feb 06, 2017 this lecture talks about flow nets and how to draw them by hand. A flow net is a graphical representation of flow of water through a soil mass.
Figure 1 shows an example of flow net construction. Determine the head at the inlet and outlet of the flow net. Section 4 the spreadsheet tool has further been used to analyse other worked examples from the main text. A flow net is drawn by hand as a demonstration, and various calculations including head, pressure, uplift force, and gradient are. The use of these design aids is illustrated by a series of examples, and the results are compared with moreexact flow net solutions obtained by tho use of electric analogs. There is also a student version that is either free or very cheap. You can see much better quality flow nets in textbooks. Seepage lecture geotechnical engineering soil mechanics. Notice that one of the flow paths crosses the piezometric line, which confirms that the zeropressure line is not a flow boundary in a saturatedunsaturated flow system. It is possible, by means of a flow net, to calculate the hydrostatic uplift on a structure such as a dam or barrage, the amount of seepage. Unconfined flow two basic methods to determine phreatic surface. It is usually easier to start by drawing the flow lines. Add seep3d to seepw to analyze 3d groundwater flow using the same comprehensive.
Determine the quantity of seepage under the dam and plot the distribution of uplift pressure on the base of the dam. Texts on engineering seepage, such as harr 1962 or cedergren 1967, provide hints on graphical construction and include many examples of steadystate, freesurface flow nets. Pe06seepageflownets solved problems in seepage and flow. The effective stress at point a, if void ratio equal to 0. Field examples are used to show how this technique can be used to diagnose design flaws. In my seepage and drainage class i use the program seepw. In hydrology, seepage flow refers to the flow of a fluid water in permeable.
Crosssectional flow net of a homogeneous and isotropic aquifer hubbert, 1940. The flow net properties of the flow net and equations for estimating discharge quantity, seepage pressure, and discharge gradient are presented in figure 1. Clear explanations of darcys law, permeability, and other coreconcepts seepage analyses and drainage designs for earth dams, levees,foundations, earth slopes, roads, airfields, streets, parking lots,and more information on contemporary topics, including wick drains,fin drains. It is a cadbased, windows program, very easy to use but very powerful steadystate, transient, saturated and unsaturated flow. Determine the amount of seepage that occurs under steady state flow conditions and calculate the pore pressure at the mid point of the. Effects of boundary condition on shape of flow nets. Flow nets are applicable for the study of cutoff walls and wellpoints, or. In the flow net there are 47 flow channels and 15 equipotential drops.
Because of changes of geology and other seepage rules have given necessary. It is a curvilinear net formed by the combination of flow lines and equipotential lines. The flow net is an excellent tool for evaluating the effects of seep. Use this procedure to estimate seepage quantity and distribution of pore water pressures in twodimensional flow.
How high water will rise in piezometers at points a, b, c, and d. Flow nets square ideally, the cells in the flow net should be square flow net example flow lines are to upstream ground surface flow lines are to face of toe filter faces equipotential lines are to impervious boundaries flow lines are to equipotential lines everywhere. Jun 21, 2017 a flow net is a graphical representation of the pattern of the seepage or flow of water through a permeable soil. The coefficient of permeability of the foundation soil is 25 x 105 ms. Seepage and flow nets theory of structures eurocode standards. Let us consider a state of plane seepage as for example in the earth dam shown in figure 1. Enrol today in our site and get access to our study package comprising of video lectures, study material, practice questions and test. The pipe, which is filled with sand has a gross internal cross sectional area of 0. Anisotropy in seepage analyses geoslope international. From the flow net, the total head at any point can be computed.
Seepage, drainage, and flow nets, 3rd edition wiley. Pdf on apr 1, 2016, yos simanjuntak and others published seepage flow out of a pervious concretelined pressure tunnel find, read and cite all the research you need on researchgate. The technique is shown to be useful in both low velocity darcy and high velocity nondarcy flow regimes. These are compared with the solutions obtained by flow net sketching. The objective of this laboratory is to introduce you to flow nets and the construction of equipotential maps. Dec 14, 2016 seepage theories khoslas method of independent variables for determination of pressures and exit gradient for seepage below a weir or a barrage in order to know as to how the seepage below the foundation of a hydraulic structure is taking place, it is necessary to plot the flow net. The definitive practical guide to understanding and solving seepageand drainage problems now in its third edition, this unique resource offers simplemethods for analyzing and designing seepage and groundwater controlsystems for all major types of civil engineering works. Modify the net so that it meets the conditions outlined above and so. Two layer flow system with sand below ku kl 1 50 two layer flow system with tight silt below flow nets for seepage from one side of a channel through two different anisotropic twolayer systems.
Dec 11, 2016 how to draw flow net seepage by hand last updated on sat, 10 dec 2016 soil mechanics impermeable fig. In seepage problems the velocity of flow is very small and the velocity head is. Science and technologies related to basic structures. Appropriately contouring these results produces the desired flow lines, and the flow net is complete. Introduction to seepage and drainage cedengineering. Draw a coarse net which is consistent with the boundary conditions and which has orthogonal equipotential and flow lines. The accuracy of the computation of hydraulic quantities, such as discharge and pore water pressure, does not depend much on the exactness of the flow net. A flow net is a 2d diagram of equipotentials lines of equal head and flow lines. Figures 2 and 3 illustrate flow directions at entrance boundaries, exit boundaries, and across boundaries between soils of different permeabilities. Between the upstream and downstream equipotentials the total head loss is 400 m.
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