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

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In the study, soil borings used in the design of the metro subway system were used for makingcomparisons between SPT N-values and the shear strength of fine grained soils. The studyconcluded that there is a correlation between the SPT N-value and the shear strength of finegrained soils. However, sensitive clays indicate less correlation because of their dependence onmoisture content. From the above information, it is concluded that if no test was performed onthe cohesive soils, the following relationships in Table 2.2 could be used:TABLE 2.2 Relationships Between Shear Strength and N-values for Cohesive SoilsType of ClayHigh plasticity (CH)Medium plasticity (CL)Low plasticity and clayey silt (SC-ML)Cohesion (tsf)c = 0.13 Nc = 0.076 Nc = 0.038 N2-8
CHAPTER IIIAVAILABLE BEARING CAPACITY EQUATIONSDue to extensive research in the topic of bearing capacity, numerous methods of analysishave been developed. The research started by Terzaghi (1943) and was followed by Skempton(1951), Meyerhof (1951), Hansen (1961), De Beer and Ladanyi (1961), Meyerhof (1963),Hansen (1970), Vesic (1973, 1975), and others. The most popular and widely used bearingcapacity equations in practice today are the Terzaghi and AASHTO equations. The following isa short description of each.3.1 Terzaghi’s Bearing Capacity EquationsThe Terzaghi (1943) set of equations were the first to be proposed. They have been verywidely used since then and continue to be in great use mainly because of their relative simplicity.Terzaghi used trial wedges of the type assumed by Prandtl (1921), expanding and improving onPrandtl’s theory. The expressions of bearing capacity obtained by Terzaghi are:Long footings:q ult= cN + γDN+ 0. γBN(3.1)c q5γSquare footings:q ult= 1.3cN+ γDN+ 0. γBN(3.2)c q4γCircular footings:q ult= 1.3cN+ γDN+ 0. γBN(3.3)c q3γwhere:c = cohesion of soilγ = unit weight of soilD = depth of foundation3-1
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: Fig. 2.3Relationship between SPT N-
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 and 32: x1 and x2 factors180160140120100806
Page 33 and 34: q ult= γ 1x 1D + γ 2x 2Bwhere γ
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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