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PAD FOOTING DESIGN AND

CONSTRUCTION PART 1

PREPARED BY AHMAD HAKIMI BIN MAT NOR

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BEARING CAPACITY ANALYSIS

BEARING

CAPACITY

FAILURE

Foundation

consideration rest

on dense sand @

stiff cohesive soil(a) General shearfailure

(b) Local shear

failure

(c)Punching shear

failure

Foundation

consideration rest

on sand @ clayey

soil of medium

compaction

Foundation

consideration rest

on fairly loose soil

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Plastic Analysis Of Bearing Capacity (Terzaghi method)

III IIII

IIII

Ø

Zone I : Triangular Zone

Zone II : Zone of Radial Shear 

Zone III : Rainkine Passive Zone

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Allowable bearing capacity (qa)

The allowable bearing capacity , qa is the loading per unit area thatthe soil is able to support without unsafe movement,

Where:

qa = allowable bearing capacity

qult = ultimate bearing capacity

FS = safety factor

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Ultimate bearing capacity in cohesive soil (qult)

The basic principle in evaluating the bearing capacity of cohesive soil (clayey) soil

is best introduced by Terzaghi (Terzaghi and Peck,1967).

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Note : e is the base of natural

logarithms- approximately

2.71828

The line on figure 9.4

representing Nγ was found by

plotting values determined in

studies Meyerhof (1955)

Nγ=22

Nq=23

Nc=36

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Local Shear Failure

C’ and Ø’

qu = c’N’c + γ1Df  N’q + 0.5γ2 BN’γ

Shear Strength --- C and Ø

Note:

- Loose sand and soft clay = Local shear failure

-Dense Sand and Hard Clay = General shear failure

@-Ø ≥36   ̊= General shear failure

-Ø ≤ 29   ̊= Local shear failure

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Rajah 9.4

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EFFECT OF WATER TABLE ON BEARING

CAPACITY

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Case III. When the water table is located so that d ≥ B, the water will have no

effect on the ultimate bearing capacity

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END