Graphical Determinations of Earth Slope, Retaining Walls and Dams

The author states that this book ls intended for students and not for professional engineers, but the subject treated is one of deep interest to civil engineers as well. The stability of earth slopes is considered, in the first chapter, on the basis of the angle of natural slope due to the internal friction of the material, and also by including with the friction the cohesion of the soil which is found to exist in old well settled banks. The subject is treated both graphically and analytically. The slope of equal stability as affected by height of bank when cohesion is considered is then constructed, bringing out the steep top and flat bottom, which is characteristic of the natural earth slope. Comparisons are then made of the amounts of excavation per lin. ft. for a 50-ft. cut taken out to different uniform slopes, with those obtained for corresponding slopes of equal stability or equal safety and the saving in excavation shown. The pressure of earth against retaining walls is taken up graphically in Chapter II., using the method given by Rebhann. The treatment includes the irregular profile or surcharge, also the effect of cohesion for walls supporting firm undisturbed earth free from water and frost. The passive pressure or the resistance of earth to motion from the horizontal thrust of say an arch is also considered. The analytical method from Rebhann is developed in Chapter III., while the formulas of Rankine and Weyrauch are given without derivation. No account is taken of cohesion in this chapter. At the close of the chapter three tables are given showing the close numerical agreement between the three methods for heights of wall from 25 to 85 ft. for different batters and for different surcharges. The design of retaining walls is considered in Chapter IV. The method is extended to walls with buttresses and counterforts, the latter both with and without relieving arches, but it is not extended to reinforced-concrete construction. Masonry dams are briefly discussed in the last chapter. The stability of earth slopes and the earth pressure against retaining walls are well presented in the first three chapters. Attention is called to earth slopes as they actually occur and to the assumptions made by Rebhann in developing the methods used in finding the pressures against retaining walls. The chapter on the design of retaining walls would have been of greater value to the student or to the young practicing engineer if it had been put more in touch with actual practice by considering the effects of character of soil, drainage, frost, and even of foundations upon stability, as was done for earth slopes, and by a. few illustrations from practice. These applications would have been especially valuable in showing the application of theory to practice, an application which is questioned by many engineers. An extension of the chapter to reinforced-concrete retaining walls in connection with the European system of buttresses, counterforts and relieving arches would have greatly enhanced the value of the book, even if added at the expense of the chapter on dams. The treatment of masonry dams is brief, but a pretty good general idea is given of the methods of computing stability and of determining practical cross-sections with illustrations from European and American practice. The typography is excellent. -Engineering News, Volume 60 [1908]