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

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TABLE 2.1 Angle of Friction from Different EquationsN 60 Eq. 2.1 Eq. 2.2 Eq. 2.32 27.70 27.604 28.29 28.206 28.88 24.49 28.808 29.46 25.95 29.4010 30.15 27.25 30.0012 30.62 28.42 30.6014 31.19 29.49 31.2016 31.76 30.49 31.8018 32.33 31.43 32.4020 32.88 32.32 33.0022 33.44 33.16 33.6024 33.98 33.97 34.2026 34.53 34.75 34.8028 35.08 35.49 35.4030 35.61 36.21 36.0032 36.15 36.91 36.6034 36.08 37.58 37.2036 37.20 38.24 37.8038 37.72 38.87 38.4040 38.24 39.49 39.0042 38.75 40.09 39.6044 39.25 40.69 40.2046 39.76 41.27 40.8048 40.26 41.83 41.4050 40.75 42.39 42.002.4 Cohesion of Cohesive SoilsThe SPT N-value for a given clay may vary significantly with seasonal fluctuations in thewater table. Thus, the values may fall short of providing information on the characteristics of theclay, mainly its strength. There are correlations that estimate the undrained shear strength ofclay as a function of the SPT N-value. These correlations are not as meaningful for sensitive andmedium to soft clays where effects of disturbance during sampler penetration may cause alowering in the SPT N-value.2-4
The Japanese “Road Bridge Specifications” (Shioi and Fukui, 1982) offer a correlationbetween the cohesion, c, and the SPT N-value for cohesive soils:c = ( 0.061 to 0. 102)NtsfSowers (1979) presented the relationship between the SPT N-value and the underained shearstrength S u that is shown in Fig. 2.2. The relationship can be represented by:For clays with high plasticity:S u= ( 0.102 to 0. 179)NtsfFor clays with medium plasticity:S u= ( 0.051to 0. 102)NtsfFor clays of low plasticity and clayey silts:S u= ( 0.026 to 0. 051)NtsfIn Fig. 2.3 the NAVFAC, 1982 relationships between the SPT N-value and the unconfinedcompressive strength are presented. They can be summarized as:An average relationship for all clays by Terzaghi and Peck: c = 0.066N tsfFor clay of high plasticity, Sowers,c = 0.13N tsfFor clays of Medium plasticity, Sowers,c = 0.076N tsfFor clays of low plasticity and clayey silts, Sowers,c = 0.038N tsfTo add further insight into the correlation between the N-value and the shear strength offine grained soil, a study by Henmueller (2001) was undertaken and is presented in appendix B.2-5
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: Fig. 2.1Correlation between frictio
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 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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