Transcript Pertemuan 05 Daya Dukung Tanah Matakuliah : S2094 / Rekayasa Pondasi Tahun

Matakuliah : S2094 / Rekayasa Pondasi
Tahun
: 2005
Versi
: 1.1
Pertemuan 05
Daya Dukung Tanah
Shallow Foundations
Bearing Capacity
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The problems of soil mechanics can
be divided into two principal groups stability problems and elasticity
problems
- Karl Terzaghi, 1943
Karl Terzaghi (1883-1963)
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Father of modern soil mechanics
Born in Prague, Czechoslovakia
Wrote “Erdbaumechanick” in 1925
Taught at MIT (1925-1929)
Taught at Harvard (1938 and after)
Karl Terzaghi at Harvard, 1940
Bearing Capacity Failure;
Fargo Grain Elevator, N. Dakota
Transcosna Grain Elevator, Canada
Oct. 18, 1913
West side of foundation sank 24-ft
Stability Problem
Bearing Capacity Failure
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Bearing Capacity Analysis
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How do we estimate the maximum
bearing pressure that the soil can
withstand before failure occurs?
Bearing Capacity Failures
Types/Modes of Failure
 general
shear failure
 local shear failure
 punching shear failure
General Shear Failure
Punching Shear Failure
Model Tests by Vesic (1973)
General Guidelines
Footings in clays - general shear
 Footings in Dense sands ( Dr> 67%)
-general shear
 Footings in Loose to Medium dense
(30%< Dr < 67%) - Local Shear
 Footings in Very Loose Sand ( Dr < 30%)punching
shear

Bearing Capacity Formulas
qult  N c su   zD
Terzaghi Bearing Capacity
Formulas
Terzaghi Bearing Capacity
Formulas
For Continuous foundations:
qult  cN c   zD N q  0.5 BN 
For Square foundations:
qult  1.3cN c   zD N q  0.4 BN 
For Circular foundations:
qult  1.3cN c   zD N q  0.3 BN 
Bearing Capacity Factors
Terzaghi Bearing Capacity
Formulas
D
B
 No sliding between footing and soil
 soil: a homogeneous semi-infinite
mass
 general shear failure
 footing is very rigid compared to soil