Retaining walls; their design and construction . st (see pages 11-15), may safely be apphcd to deter-mine the thrust. ^ Earth Pressure, Walls and Bins, pp. 90, 66 RETAINING WALLS That the wall be self-sustaining while under construction, itis necessary that its center of gravity projected down, alwaysfalls within the base. To effect this, denote the ratio of thewidth of base to height of wall (a parallelogram is the only typeof section discussed in detail here) by k. That the wall be self-sustaining, it is necessarythat k be greater than tan in the former pages, adirect method of det
Retaining walls; their design and construction . st (see pages 11-15), may safely be apphcd to deter-mine the thrust. ^ Earth Pressure, Walls and Bins, pp. 90, 66 RETAINING WALLS That the wall be self-sustaining while under construction, itis necessary that its center of gravity projected down, alwaysfalls within the base. To effect this, denote the ratio of thewidth of base to height of wall (a parallelogram is the only typeof section discussed in detail here) by k. That the wall be self-sustaining, it is necessarythat k be greater than tan in the former pages, adirect method of determiningupon the ratio k for anycharacter of loading, predi-cated upon the resultant in-tersecting at the outer edgeof the middle third may befound for this type of the following work theearth pressure coefficient isK, defined by equation (25).In view of the fact that theangle h is now negative, Table 13 has been prepared giving thevalues of this coefficient A for negative values of the angle 6. The thrust moment is T XAO (76) From (24). Fig. 31.—Design of revetment wall. gh-K 1 + 2c AO = EF = ED - FD. ED = Bh cos{ - b) FD = {Bh tan fe + ^ A70 sin ( -h) - {3B tan h + 2k) sin(<^ - 6)] The stal)ility moment of the wall (both of the moments aretaken about the outer edge of tlie middle third, 0) is vikh- L tan h + kh/2 \ kh^ A-/i/3J = m ! (3 tan h + k) Equating tliese two moments, and writing tiio resulting equa-tion as a quadratic in k k + Rk = S (77) DESIGN OF GRAVITY WALLS lere R S = 3 tan 6 + 2s(l + 2c) sir i{ -b) s is the ratio — 67 (78)(79) Table 13 b 0 = O° = 30° 6 = 5° 6=10° 6 = 5° 6 = 10° 6 = 5° 6=10° 0 .35 .25 .30 .21 .23 .17 .2 .47 .37 .40 .29 .31 .23 .4 .57 .46 .48 .37 .37 .29 Table 14 gives a series of values of the ratio, k, based on theabove equation for several values of b and . Revetment wallsare usually built o
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