Matakuliah: S2094 / Rekayasa Pondasi

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Pertemuan 06Daya Dukung Tanah

• Matakuliah S2094 / Rekayasa Pondasi
• Tahun 2005
• Versi 1.1

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Further Developments

• Skempton (1951)
• Meyerhof (1953)
• Brinch Hansen (1961)
• De Beer and Ladanyi (1961)
• Meyerhof (1963)
• Brinch Hansen (1970)
• Vesic? (1973, 1975)

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Vesic? (1973, 1975) Formulas
Shape factors. Eq. 6.14, 6.15 and 6.16 Depth
Factors . Eq. 6.17, 6.18 and 6.19 Load
Inclination Factors . Eq. 6.20, 6.21 and
6.22 Base Inclinations factors .. Eq. 6.25 and
6.26 Ground Inclination Factors. Eq. 6.27 and
6.28 Bearing Capacity Factors . Eq. 6.29, 6.30
and 6.31
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Bearing Capacity of Shallow Foundations

• 6.3 Groundwater Effects
• 6.4 Allowable Bearing Capacity
• 6.5 Selection of Soil Strength Parameters
• 6.6 Local Punching Shear Cases
• 6.7 Bearing Capacity on Layered Soils
• 6.8 Accuracy of Bearing Capacity Analyses
• 6.9 Bearing Capacity Spreadsheet

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Allowable Bearing Capacity

• .. Allowable Bearing Capacity
• F . Factor of safety

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Factor of Safety

• Depends on
• Type of soil
• Level of Uncertainty in Soil Strength
• Importance of structure and consequences of
  failure
• Likelihood of design load occurrence

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Minimum Factor of Safety
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Selection of Soil Strength Parameters

• Use Saturated Strength Parameters
• Use Undrained Strength in clays (Su)
• Use Drained Strength in sands,
  
• Intermediate soils that where partially drained
  conditions exist, engineers have varying
  opinions Undrained Strength can be used but it
  will be conservative!

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Accuracy of Bearing Capacity Analysis

• In Clays ..Within 10 of true value (Bishop and
  Bjerrum, 1960)
• Smaller footings in Sands. Bearing capacity
  calculated were too conservative but
  conservatism did not affect construction cost
  much
• Large footings in Sands Bearing capacity
  estimates were reasonable but design was
  controlled by settlement

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Accuracy Bearing Capacity Analysis