A geotechnical investigation tells you what is under your site before you design on it. It reveals the soil and rock layers, the groundwater level and the strength of the ground, so foundations are neither unsafe nor over-designed.
When you need one
Buildings, bridges, industrial plants, roads, tanks and retaining walls all depend on ground conditions. An investigation is most useful early, before the layout and budget are fixed, because ground problems found later are usually far more expensive to solve.
The process, step by step
- Desk study and site visit: existing maps and records, access, nearby structures and visible signs of trouble.
- Planning: the number, location and depth of boreholes or test pits, based on the structure, its loads and the site. Soil testing for buildings explains this for smaller projects.
- Drilling and sampling: disturbed and undisturbed soil samples, and rock core where rock is met.
- Field tests: commonly the SPT, with CPT, plate load tests or permeability tests where needed.
- Laboratory testing: classification, strength, consolidation and chemical tests.
- Analysis and report: the ground model and foundation recommendations.
Indian Standards commonly used
- IS 1892: code of practice for subsurface investigation
- IS 2131: standard penetration test
- IS 1888: load test on soils
- IS 2720 (series): methods of test for soils
- IS 1498: soil classification
- IS 6403 and IS 8009: bearing capacity and settlement of shallow foundations
What a good report tells you
- Borehole logs and the soil and rock profile
- Groundwater level at the time of investigation
- Field and laboratory results
- Recommended foundation type and depth
- Safe bearing capacity and expected settlement
- Any special risks, such as expansive soil, soft clay or liquefaction
Adding geophysics
Boreholes only show the ground at each point. Geophysical surveys such as ERT and MASW help cover the ground between them, which is useful on large or variable sites.
FAQ
How long does a geotechnical investigation take?
It depends on the number and depth of boreholes, site access and the laboratory programme. We confirm a schedule once we have seen the scope.
Is a geotechnical investigation the same as soil testing?
Soil testing is one part of it. A full investigation also covers drilling, field tests, groundwater and engineering recommendations.
Who needs the report?
Your structural engineer uses it to design foundations. Contractors and authorities may also ask for it.
Talk to our team
Planning a project? Call +91 98718 04288, email contact@geowingseng.com or see our geotechnical investigation service.
