Objectives of investigation for hill road

Engineering geology is the application of geological principles and data to civil engineering so that works are planned, designed and built safely, economically and in harmony with the environment.

Major objectives of investigation for a hill road

1. Selection of the best alignment: compare alternative routes and choose the most stable, shortest and economical one, avoiding active landslides, fault zones and unstable slopes.
2. Identification of rock and soil types along the route, their strength and weathering, to decide cut slope angles and excavation methods (manual, ripping or blasting).
3. Study of geological structures: dip and strike of beds and joints relative to the road cut; whether discontinuities dip out of the slope (risk of planar or wedge failure).
4. Landslide and slope stability assessment: mapping existing and potential slides, rockfall and debris-flow areas; deciding treatment.
5. Groundwater and drainage: locating springs, seepage and gullies; planning side drains, culverts and subsurface drainage.
6. Foundation conditions for bridges, culverts and retaining walls: depth to bedrock, bearing capacity and scour.
7. River training: studying river erosion, flood levels and bank stability where the road runs along rivers.
8. Material survey: finding quarries for aggregate, borrow areas for fill and sources of sand.
9. Hazard evaluation: seismic zone, active faults, debris flows, glacial lake outburst floods in high areas.
10. Design of stabilisation measures: retaining walls, breast walls, gabions, bioengineering, anchors.
11. Environmental protection: minimising slope disturbance and planning safe disposal of spoil.
12. Cost estimation: reliable quantities of rock and soil excavation, and of protection works.

These objectives are met through desk study, aerial photograph interpretation, engineering geological mapping along the alignment, test pits and boreholes at critical sites, and geophysical profiling.