Detail stage of EG site investigation

The detail stage (detailed design stage) is the final stage of investigation after the site or alignment has been selected, and gives the complete and accurate geological data for the final design and construction.

Activities

1. Large-scale engineering geological mapping (1:1,000-1:500) of the site, with detailed structural study.
2. Dense sub-surface exploration: closely spaced core drilling (including supplementary holes), test pits, trenches, shafts and adits.
3. Geophysical surveys to fill the gaps between holes.
4. In-situ tests: permeability (Lugeon), plate load, shear, flat-jack, SPT and in-situ stress tests.
5. Laboratory tests on rock and soil for strength, deformability, durability and index properties.
6. Rock mass classification (RMR, Q, GSI) and design parameters.
7. Groundwater study: observation wells, piezometers.
8. Detailed investigation of construction materials and their reserve.
9. Geological sections and 3D model; final report with recommendations for foundation treatment, slope support, grouting, excavation and monitoring.

Scale and spacing are chosen from the importance of the structure and the geological complexity.