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Geological investigation of tunnel and road

Short answer

Tunnel investigation proceeds from desk study and remote sensing for alignment selection, to field mapping, seismic refraction and boreholes for rock class and support prediction, and face mapping during construction. Road investigation uses aerial photos to avoid landslides, geological traverses, boreholes at bridges and cuts, and slope stability analysis for cut design.

Discuss the geological investigation of tunnel and road.

Tunnel

  1. Reconnaissance: desk study, air photos and satellite images, geological map; identify possible alignments and portal sites.
  2. Preliminary: field mapping along the alignment, measurement of joints, faults and folds; seismic refraction and resistivity; a few boreholes at portals and at deep cover; rock tests.
  3. Detailed: large-scale mapping, core drilling along the axis (spacing based on geology), packer tests, groundwater observation, geological longitudinal section with rock classes (RMR/Q), prediction of support, water inflow, squeezing and rock burst. Pilot tunnel or adits for a long tunnel.
  4. During construction: face mapping, probe drilling, monitoring.

Road

  1. Reconnaissance: study of maps, aerial photos; identify landslides, unstable zones, river crossings.
  2. Preliminary: geological traverse along alternatives, mapping of rock type, structure, slope stability and hydrology; select alignment.
  3. Detailed: large-scale mapping, test pits and trenches, boreholes at bridges, high cuts, embankments; geophysics at critical sections; slope-stability analysis with joint orientation (stereonet); drainage design; materials survey for aggregate and borrow.
  4. Construction: inspect cuts, treat failures, monitor slopes.

✓ Answer checked by Claude Opus 5.5 (high effort)

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