Geotechnical Investigations and Geotechnical Report (Soils Report)
The geotechnical report communicates the site conditions, design, and construction recommendations. Project site investigations aim to provide specific information on subsurface soil, rock, and water conditions. The geotechnical engineers review and analyze the data from the site investigations to arrive at the design and construction recommendations.
The objectives of site investigation or exploration are as follows:
- Determine the bearing capacity of the soil
- Determine the stability of the faces of the excavation
- Determine drainage characteristics of soil
- Construction methods for excavating the soil and/or rock
- Determine the depth of the water table, the impact on the structure, and the method for dewatering the excavation
- Determine compressibility of soil and impact of foundation settlement
Geotechnical reports are typically required and must be reviewed for items of work that relate to:
- Cuts and embankments
- Embankments over soft ground
- Landslide corrections
- Retaining structures
- Structure foundations (spread footings, piles, drilled shafts)
- Ground improvement techniques
- Material sites (borrow sites)
- Others
While the geotechnical report content and format may vary from one report to another, all geotechnical reports contain certain basic essential information, including:
- Summary of all subsurface exploration data, including subsurface soil profile, exploration logs, laboratory or in situ test results, and groundwater information;
- Interpretation and analysis of the subsurface data;
- Specific engineering recommendations for design;
- Discussion of conditions for the solution of anticipated problems; and
- Recommended geotechnical special provisions.
The soil boring log provides information about the soil types, the depth of each soil type layer, the strengths of the soil at each layer, and the groundwater table. The rock core log provides information about the type of rock encountered, its compressive strength, and its consistency.
