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Types and methods of site investigation

Short answer

Site investigation uses surface methods (geological mapping, remote sensing) and sub-surface methods (test pits, boreholes, geophysical surveys like seismic refraction and electrical resistivity). In situ and lab tests provide engineering properties, and results are compiled in logs and reports.

Describe the types and methods of site investigation.

Site investigation is carried out in stages (reconnaissance, preliminary, detailed) using surface and sub-surface methods.

A. Surface investigation

  1. Direct methods: field geological mapping, traversing, measurement of strike/dip and joints, outcrop study, geomorphological mapping, study of existing cuts and landslides.
  2. Indirect methods: study of topographic maps, aerial photographs and satellite images (remote sensing), GIS, and review of earlier reports.

B. Sub-surface investigation

  1. Direct methods:
    • Test pits and trenches: to 3-5 m depth; for soil and shallow rock.
    • Shafts, adits and drifts: to inspect rock in tunnels and dam abutments.
    • Boring (auger, wash, percussion) and core drilling: to get samples and rock quality (RQD); depth as required.
    • Sampling: disturbed and undisturbed samples.
  2. Indirect methods: geophysical exploration:
    • Seismic refraction (depth of bed rock, velocity),
    • Electrical resistivity (soil/rock layers, groundwater),
    • Gravity, magnetic and ground penetrating radar.

C. In-situ and laboratory tests

Standard penetration test, plate load test, permeability (Lugeon/packer) test, shear test, rock mechanics tests and soil tests.

D. Reporting

Logs, geological sections, maps and recommendations.

✓ Answer checked by Claude Opus 5.5 (high effort)

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