Updating Bearing Capacity – SPT Graphs - Maryland State Highway ...

q ult= γ 1x 1D + γ 2x 2Bwhere γ 1 represent the unit weight of soils above the footing baseandγ 2 represent the unit weight of soils below the footing baseCase 1 Z w > BFor both γ 1 and γ 2 use the dry unit weight γ d , water table has no effect on the bearing capacity.Case 2 Z w < BFor γ 1 , use γ d , and for γ 2 useγ2= γbZw+B( γ − γ )dbwhere γ b , buoyant unit weight of soils equal the saturated unit weight γ sat minus the unit weightof water γ w , i.e.,γb= γsat− γwCase 3 Z w ≤ 0For γ 1 use γ d up to the water table elevation, and γ b up to the elevation of the footing base, and forγ 2 use γ b .4.3 Graphs for Footing on Cohesive Soils4.3.1 Wall FootingThe AASHTO equation:q 0+ qN s b iult= cNcscbcic+ .5γBNγsγbγiγqqq qwill have: i) for ϕ = 0, N c = 5.14, N q = 1.0 and N γ = 0.0ii) s c = s q = s γ = 1 for L > 5Biii) i c = i q = i γ = 1 for vertical loadandiv) b c = b q = b γ = 1 for horizontal base4-6