Retaining walls; their design and construction . a basis of comparison with the formulas developed later,a table of values of d for the several values of the angle h is givenin Table 1. To summarize briefly the results above, it may be said thatequation (14) is the Rankine expression for the thrust of an earthwith an angle of repose of 30° whose upper surface is a horizontalplane. The former remarks upon the usual nature of embank-ments as found in actual practice justify a blanket assumption of30° for this angle of repose and the resulting simplification of thethrust expression strengthens th
Retaining walls; their design and construction . a basis of comparison with the formulas developed later,a table of values of d for the several values of the angle h is givenin Table 1. To summarize briefly the results above, it may be said thatequation (14) is the Rankine expression for the thrust of an earthwith an angle of repose of 30° whose upper surface is a horizontalplane. The former remarks upon the usual nature of embank-ments as found in actual practice justify a blanket assumption of30° for this angle of repose and the resulting simplification of thethrust expression strengthens the reasons for the selection of thatparticular value of the angle of repose. For a wall with slopingback retaining a fill of shape shown in Fig. 5 equation (14) givesthe expression for the thrust. The computation of this thrust isto be aided by the use of Table 1. Coulomb Method of Maximum Wedge of Sliding.—The sameassumptions as to the properties of the id(!al earth mass are madeas were made in the preceding theory. Referring to Fig. 6 any. Fig. 6.—Method of niaximutn wedge of sliding. prism of earth AFC, where AC makes an angle a with the hori-zontal, which is greater than the angle of repose 0, will tend toslough away from the remaining earth bank and will thereforerequire a retaining wall with back AF to hold it. In this prism of 12 RETAINING WALLS earth the forces acting upon it are its weight G, the reaction ofthe thrust T upon the wall and the reaction of its pressure Qupon the remaining bank. As different wedges of possible slidingare selected, some one wedge will produce the maximum thrustupon the wall AF, which is the actual thrust sought. From the equilibrium of the figure, the forces T, G and Q,are concurrent, , must meet in a common point. From thelaw of concurrent forces T/sin t = G/sin g = Q/sin q. t, g and q are the angles asshown in the figure. G is the weight of the irregular prism AFEC and is resolved by themethods of equivalent figures (any elementa
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