loading - Geotechnical Investigation and Design Tables - page 306

24.3 Construction loads
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Wheel vehicles provide the greatest load.

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Tracked vehicles may be heavier, but provide a reduced load. This is useful in
trafficking low strength areas.

Table 24.3 Typical wheel loads from construction traffic.

Equipment Size Approximate mass Tyre inflation pressure (kPa)

Fully laden (tonnes) Per wheel (tonnes)

Small 25 6 200-400

Scrapers

Large 110 28 500-600

Small 25 4 350-700

Dump trucks

Large 80 20 600-800

24.4 Ground bearing pressure of construction equipment
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The table above is simplified below with some additional equipment shown.

Table 24.4 Ground bearing pressure.

Type of equipment Typical bearing pressure (kPa)

Small 60

Bulldozer

Large 70

Wheeled tractor 180

Small 150

Loaded scraper

Medium 200

Large 300

Sheepsfoot roller 1750

24.5 Vertical stress changes
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Soil stresses decrease with increased distance from the loading.

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The shape and type of the foundation, and the layering of the underlying material
affects the stress distribution.

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The table below is for a uniform elastic material under a uniformly loaded flexible
footing. These Boussinesq solutions are for a uniform pressure in an isotropic
homogeneous semi-infinite material.

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There is a 10% change in normal stress at approximately 2B (square foundation).
Hence the guideline for the required depth of investigation (Refer Chapter 1).

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For a strip footing the 10% change in stress occurs at approximately 6B.