Movements - Geotechnical Investigation and Design Tables - page 293

Movements

23.1 Types of movements
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Some movements typically occur in practice, ie stress and strain are interrelated.
If the load is applied and soil resistance occurs, then some nominal movement is
often required to mobilise the full carrying capacity of the soil or material.

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The large factors of safety in the working stress design, typically captures the
acceptable movement, ie deformations are assumed kept to an acceptable level.
Limit equilibrium and conditions can then be applied in the analysis. However,
many design problems (eg retainingwalls) should also consider deformationwithin
the zone of influence.

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In the limit state design, movements need to be explicitly checked against allowable
for the serviceability design case.

Table 23.1 Types of movement.

Design application Parameter Typical movement

Shallow foundations Allowable bearing capacity 25 mm for building

Deep foundations Shaft friction 10 mm for shaft friction to be mobilised

Retaining walls Active and passive earth 0.1% H for K a to be mobilised in dense sands

Pressure coefficient 1% H for K p to be mobilised in dense sands

Reinforced soil walls Frictional and dilatancy to 25 to 50 mm for geogrids

transfer load to soil 50 to 100 mm for geotextiles

reinforcement

Pavements Rut depth based on a 20 mm rut depths in major roads - paved

strain criterion related to 100 mm rut depths in mine haul roads

number of repetitions

Embankment Self weight settlement 0.1% height of embankment

Drainage Total settlement Varies with crossfall. 100 to 500 mm

23.2 Foundation movements
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The immediate settlement is calculated using elastic theory.

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Consolidation settlements occur with time as water is expelled from the soil.