Stress Distribution 2

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Stress Distribution

in Soil Mass–

Part 2

KAEA 3233 - SOIL MECHANICS II

Dr. Tan Chee GhuanDepartment of Civil Engineering

Faculty of Engineering

University of Malaya1


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2

Pressure distribution diagrams

• Stress varies along depth as well as

horizontal distance.

• Vertical pressure on a given

horizontal plane is same in all

directions at equal radial distance

from the axis of loading.• An ‘isobar’ is a stress contour or a

curve which connects all points

below the ground surface with the

same vertical stress.• An isobar is a spatial curved

surface and resembles a bulb in

shape. The stress isobar is also

called ‘pressure bulb’.

Isobar


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Pressure distribution diagrams


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Significant depth


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Significant depth


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Example 2

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A single concentrated load 1000 kN acts at the ground surface.

Construct an isobar for a vertical pressure of intensity 40 kN/m2. Use

Boussisesq formula.


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Vertical Stress Caused by a Line Load

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• Road, railway traffic, walls and etc.

• The vertical stress in a soil mass due to a vertical

line load can be obtained using boussinesq’s

solution.


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Vertical Stress Caused by a Strip Load

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• Exterior Wall Foundation


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Vertical Stress Caused by a Circular Load

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Vertical Stress Caused by a Circular Load


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Example 3

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A ring footing of external diameter 8m and internal diameter 4m

rests at a depth of 2m below the ground surface. It carries a load ofintensity 150 kN/m2. Find the vertical stress at a depths of 2m, 4m

and 8m along the axis of the footing below the footing base.

Stress Distribution 2

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