A soil investigation is a systematic assessment of the ground conditions at a construction site. It examines soil composition, bearing capacity, groundwater levels, and potential contamination to inform foundation design and construction planning.
Types of Soil Investigation
Geotechnical Investigation
Focuses on the physical and mechanical properties of the soil:
- Cone penetration tests (CPT) — a cone is pushed into the ground to measure resistance and determine soil layer profiles
- Boreholes — soil samples are extracted at various depths for laboratory testing
- Plate load tests — a loaded plate measures the soil’s bearing capacity at the surface
Environmental Investigation
Focuses on chemical contamination:
- Exploratory investigation — initial sampling to detect the presence of contaminants
- Detailed investigation — in-depth sampling to determine the extent and severity of contamination
- Baseline measurement — establishes a reference point before construction begins
When is a Soil Investigation Required?
A soil investigation is typically required when:
- Applying for a building permit for new construction
- Changing the use of a property (e.g. industrial to residential)
- Buying or selling land where contamination history is unclear
- Designing foundations that need to match the actual ground conditions
- Excavating or moving soil off-site
Application
Soil investigations are essential for virtually all construction projects. The results directly influence:
- Foundation type selection (shallow footings, piles, raft foundations)
- Excavation planning and dewatering strategies
- Soil disposal and reuse decisions
- Risk assessment for workers and future occupants
- Project cost estimation and scheduling
Skipping a soil investigation can lead to foundation failure, unexpected contamination costs, and regulatory penalties.
Related Terms
- Soil quality map
- Cone penetration test
- Foundation design
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