Importance of soil mechanics

Soil mechanics is the branch of engineering mechanics that describes the behaviour of soil under stress, water flow and loading. Almost every civil structure rests on, in, or is built of soil, so its design depends on soil behaviour.

Fields of application

• Foundations: finding the bearing capacity and settlement of footings, rafts and piles so a building, bridge or tower does not fail or settle too much.
• Earth structures: design of earth dams, embankments, canal banks and road/rail embankments, using soil as a construction material (compaction, permeability, strength).
• Retaining structures: earth pressure on retaining walls, sheet piles, basement walls and braced excavations.
• Slope stability: natural hill slopes, cuttings, and embankment slopes, which is vital in the hilly terrain of Nepal where landslides are common.
• Pavements: subgrade strength (CBR), drainage and frost/swelling effects for highways and airfields.
• Seepage and groundwater: flow below dams and weirs, uplift pressure, piping, dewatering of excavations.
• Underground structures: tunnels, culverts, pipelines and shafts, which need lateral earth pressure and ground movement estimates.
• Ground improvement and earthquake engineering: compaction, drainage and stabilisation; liquefaction of loose saturated sands during earthquakes.

Without soil mechanics, structures would be designed by guesswork, leading to excessive settlement, tilting, slope failure or collapse.