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Unformatted text preview: BC7 General Shear Failure Bearing Capacity: o Form of Terzaghi equation essentially correct: bearing factors and extensions improved o Desirable to analyze deeper footings (D f > B), inclined loads, eccentric loads, sloped ground, and tilted footing base o Several important solutions available: Meyerhof (1963) uses = (45 + /2) and includes shear strength in soil above footing, inclined and eccentric loads Hansen (1970) similar to Meyerhof, adds slope and tilted base Vesic (1973) similar to Hansen with modified inclination, slope, and tilt factors All three methods use same N c and N q , but have different N Do not mix the methods , compare if time & project dictate extra effort Meyerhof Bearing Capacity Equation: (for general shear failure) q u = (q c + q q + q ) = cN c cs cd ci + qN q qs qd qi + BN s d i where: q u = ultimate bearing capacity c = cohesion (q c due to c) q = stress at depth of foundation = D f (q q due to q) = average unit weight of soil under footing (q due to ) (if completely submerged, use = = b ) B = width of foundation (= diameter for circular foundation) cs , qs , s = shape factors cd , qd , d = depth factors ci , qi , i = load inclination factors N c , N q , N = bearing capacity factors Shape Factors ( s ): for ( = 0) cs + = L B 20 . 1 qs = s = 1.00 for (0 <10) interpolate between ( = 0) and ( = 10) for ( 10) cs + + = 2 45 tan L B 20 . 1 2 qs = s + + = 2 45 tan L B 10 . 1 2 Depth Factors( d ): for ( = 0) cd + = B D 20 . 1 f qd = d = 1.00 for (0 < 10) interpolate between ( = 0) and ( = 10) for ( 10) cd + + = 2 45 tan B D 20 . 1 f qd = d + + = 2 45 tan B D 10 . 1 f B Q q = D f D f Soil: , c, BC8 Inclination Factors ( i ): for ( = 0) ci = qi = i = 1.00 for ( = 0) ci = qi 2 90 1 - = i = 0 for ( > 0) ci = qi 2 90 1 - = i 2 1 - = (= 0 if > ) Bearing Factors (N): ) 2 / 45 ( tan e N 2 tan q + = b ( in radians) - = tan 1 N N q c , N c = 5.14 for...
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This note was uploaded on 09/12/2011 for the course CEG 4012 taught by Professor Staff during the Fall '08 term at University of Florida.
- Fall '08