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United States Department of Agriculture

Agricultural Research Service


item Pachepsky, Yakov

Submitted to: Soil Science
Publication Type: Other
Publication Acceptance Date: January 29, 2004
Publication Date: April 1, 2004
Citation: Pachepsky, Y.A. 2004. Seepage in soils: Principles and Applications. Soil Science. 169:314-315.

Technical Abstract: Book review. Lakshmi N. Reddi. 2003. Seepage in soils: principles and applications. John Wiley and Sons, Hoboken, NJ. Textbook for advanced undergraduate and graduate students in civil engineering, Because the author defines neither seepage nor soil in this book, I assume a reader is free to give his or her definitions, and will give definitions that I have deemed to be appropriate for the purpose of this review. Seepage in this book is the saturated water flow. Soil in this book is the superficial unconsolidated porous medium that is either man-made or naturally deposited. The book teaches laws governing seepage, provides methods to forecast seepage for particular conditions, and explains available arsenal of techniques to control seepage. The book is very timely, as most of the literature on seepage is out of print and hard to get. The book has an unusually high level of rigor. The author has made the point that understanding of subsurface hydraulics can be achieved via work with a rich set of simple analytical solutions and hand drawing flow nets. The author argues that, equipped with this knowledge, students should easily understand and confidently use canned software programs later and, more important, will be in a position to interpret with confidence results yielded by these programs. In my opinion, this approach can help students to develop an intuitive perception though hands-on experience that is not easy to obtain in subsurface hydraulics. I recall that my own understanding of seepage had a substantial boost after a hands-on experience with conductive paper models. A rigorous course is arguably more difficult for students to learn. However, the actual difficulty depends on the didactic tact and the pace of presentation. The book is almost impeccable in this respect. The introductory chapter contains a highly readable historical review of the major contributors to understanding and modeling seepage and its effects on civil engineering objects. Chapter 2 introduces the hydraulic conductivity as the most important property of soils. The commendable attention is paid to various aspects of the hydraulic conductivity concept, measurement and applications. Various estimation techniques and measurement methods are described and, where possible, compared. The concept of flow nets is introduced in Chapter 3. Both graphical methods and appropriate mathematical solutions are presented. The qualitative and quantitative effect of the graduate flow net refinement on the accuracy is illustrated. A rich assortment of flow nets covers a multitude of case studies. Mathematical solutions of two-dimensional problems in subsurface hydraulics are introduced in Chapter 4 and 5. Chapter 4 contains many useful solutions based mostly on assumptions that are valid where hydraulic head gradients are not steep. Among other materials, the chapter contains an excellent compendium of solutions developed by Don Kirkham for drainage. Another class of approximate solutions comprehensively covers seepage with free boundary and seepage faces. The Chapter 5 is different from others in requiring strong mathematical background, specifically, a knowledge of elements of complex variables. Readers who do not have such background will not be able to enjoy the beauty of solution derivations, but still will found enough usable graphical information about flow under hydraulic structures with and without sheet piles. Water transported by seepage may have its energy converted in work that will cause failures of various structures, landslides, etc. Chapter 6 gives an excellent introduction in the problem. Mathematical solutions and techniques developed/explained in Ch. 3-5 are now used to reveal the presence of critical values of internal gradients, exit pressure gradients and uplift pressure that can cause quicksand conditions, piping, heaving, and instability of slopes. The author provides rich graphic representation of possible pressure head distributions that is most helpful in visualizing possible reasons of structural failures. Designing soil filters and drainage layers remains an empirical art. The author follows the history of the design criteria and provides several sets of criteria for filter designs in a succinct narration of Chapter 7. The chapter is full of interesting and useful information. However, the chapter should answer or at least imply an answer to the question "Which set of criteria to use?" The next Chapter 8 contains an exemplary overview of geosynthetics and its use in seepage control. Chapter 8 and 9 address available technical solutions to control seepage. The author covers a remarkable volume of material in concise and comprehensive manner. The chapters are appropriately related to the theoretical background of the first chapters and empirical elements represented in Chapters 6 and 7. Empirical and semi-empirical methods to design seepage control are also well represented. The last chapter of the book considers seepage at waste containment facilities. The appropriate legal terminology is introduced. Because this type of seepage demonstrates tremendous variability in space and time, the author develops this chapter around a computer model suitable to use weather, vegetation and soil data to generate annual dynamics of seepage for typical landfills. The book is a well-written comprehensive treatise, and a civil engineer will be tempted to turn to this book many times during the career after studying it once. One warning seems to be appropriate. The book is written in such a way that a reader should not have any doubt about the applicability of equations and graphs in this book. This is a convenient way to perceive the world. However, the hydraulics of nature does not reduce to the Darcy law. Preferential flow, focused flow, concentrated flow, gravitational instability, and similar phenomena that do not follow the Darcy law, are omnipresent. It is true that our current knowledge is not sufficient to simulate those phenomena properly. Nevertheless, we know about them enough to make a future civil engineer more risk-informed and uncertainty-conscious. Esthetics and style of the book are highly commendable. The literature on seepage has a long-standing tradition of having an excellent graphics, and the book continues this important tradition. References are used in a very appropriate manner. The utility of the tables as a reference source is impressive. Overall, the book strikes the balance between rigor and utility. It is rich in material, and it can serve as a textbook both for a solid in-depth course and for a one-semester course for students who are required to know some of the basics of seepage. The book has all prerequisites to become a must-have source for civil and agricultural engineers. Yakov Pachepsky, USDA-ARS, Beltsville, MD

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