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

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4.2 Effect of Water TableUltimate bearing capacity should be determined using the highest anticipated groundwater level at the footing location. Depending on the relative position of the water table level tothe level of the base of the footing, three cases can be considered, case 1, depth of water tablebelow the footing Z w is larger than the footing width B as shown in Fig. 4.3.; case 2, depth ofwater table is smaller than B, and case 3, the water table is above the base of the footing.The equation for bearing capacity is:can be written as[ x D x B]q ult 1+ 2= γFig. 4.3Water Table Level4-5
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 <strong>Graphs</strong> 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
Page 1: UPDATING BEARING CAPACITY - SPT GRA
Page 4 and 5: SUMMARYThe graphs used by the Maryl
Page 6: 90x1 and x2 factors x1 and x2 facto
Page 9 and 10: LIST OF TABLESTablePage2.1 Angle of
Page 11 and 12: CHAPTER IINTRODUCTION1.1 General Ov
Page 13 and 14: Fig. 1.2Maryland SHA graphs for cla
Page 15 and 16: CHAPTER IISOIL PROPERTIES FROM SPT
Page 17 and 18: Fig. 2.1Correlation between frictio
Page 19 and 20: The Japanese “Road Bridge Specifi
Page 21 and 22: Fig. 2.3Relationship between SPT N-
Page 23 and 24: CHAPTER IIIAVAILABLE BEARING CAPACI
Page 25 and 26: q ult(AASHTO 4.4.7.1-1)= cNc+ 0.5γ
Page 27 and 28: TABLE 3.3 AASHTO Expressions for Fo
Page 29 and 30: 90807060Wall Footing on Granular So
Page 31: x1 and x2 factors180160140120100806
Page 35 and 36: Presumptive Ultimate Bearing Capaci
Page 37 and 38: = 466N psfFigure 4.5 and Table 4.4
Page 39 and 40: CHAPTER VAPPLICATIONS OF CURRENT AN
Page 41 and 42: Fig. 5.1 Comparison between the cur
Page 43 and 44: Fig. 5.2 Comparison between the cur
Page 45 and 46: REFERENCESMcGregor, J.A. and Duncan
Page 47 and 48: A.1. x 1 and x 2 factors as a funct
Page 49: APPENDIX BShear Strength vs. SPT-va

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