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Subsidence Investigations and Analysis
Subsidence is a major cause of failure of structures due to excessive settlement of foundations. There can be a multitude of causal factors including: Instability due to the presence of naturally occurring voids or unmapped mine shafts or workings, Settlement and compaction of soils due to percolation of water, Groundwater level fluctuations, Variation in the moisture content of clay soils
As a result of being based in East Anglia, A F Howland Associates has gained extensive knowledge and experience of subsidence events and their investigations.
Another major cause of subsidence in the East Anglian region is shrinkage/heave movements caused by variations in moisture content of clay soils. Seasonal variation can lead to near surface movement but some species of trees can cause variations in moisture content to much greater depths through the action of their root systems.
Investigation of subsidence events utilises the following methods:
- Exploratory holes (using cable percussive, window sampling or trial pitting methods) to identify features and obtain samples for laboratory analysis
- Dynamic penetration testing to investigate relative soil resistivity
- Foundation inspection pits to determine foundation construction and depth
- Structural and vegetation surveys
Subsequently, recommendations can be formulated to advise upon the most cost efficient solution to the problem.