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4.2 Causes of settlement

The main reason for development of (intolerable) settlement is the application of (excessive) structural loading on the foundation. However, settlement may develop due to direct or indirect environmental loadings and actions too such as:

  • Consolidation due to water table lowering, resulting in an increase in effective stress (Figure 4.3).
  • Changes in soil density due to dynamic loadings e.g., seismic loading of dry coarse-grained soils resulting in dynamic compaction and saturated coarse-grained soils resulting in liquefaction (Figure 4.4).
  • When a structure is founded on expansive soil deposits, heave i.e., upwards soil movement may develop due to soil moisture increase, or settlement due to soil shrinkage caused by decrease of its moisture content (Figure 4.5). Expansive soils, mainly high plasticity clays, tend to expand while absorbing water, and contract while expelling it.
  • Collapse of the structure of sensitive soils.
  • Poor compaction of fill materials.

The focus of this Part is on settlements due to application of structural loadings.

Left hand photograph shows an overpass, with a crack running from the ground to the top surface of the bridge. Right hand photograph shows a close-up of the vertical crack.
Figure 4.3. Differential settlement of a bridge due to over-pumping for irrigation purposes (author’s own photos).
Photograph of the surface of a carpark. There is a large puddle extending from beneath the cars to the foreground of the photo, and the surface of the carpark has settled as result of soil liquefaction.
Figure 4.4. Settlement due to seismic liquefaction (Soil liquefaction 2, Katori-city, Japan by katorisi, via Wikimedia Commons, is licensed under CC BY-SA 3.0).
Photograph of the side of a house with a diagonal crack in the shape of steps running from the top left-hand corner of the wall to the ground on the right.
Figure 4.5. Masonry damage due to subsidence (US Geological Survey USGS website, marked as public domain).

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Fundamentals of foundation engineering and their applications Copyright © 2025 by University of Newcastle & G. Kouretzis is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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