3.1 Soil Mechanics

Soil mechanics is the branch of Civil Engineering that studies soil's physical and mechanical properties as they relate to construction and Engineering practices. It underpins geotechnical Engineering, where soil behaviour is crucial for the design of foundations, retaining walls, embankments, and other earthworksHuman-made modifications to the landscape, such as ditches, banks, and mounds, often significant in archaeological studies.. Understanding soil mechanics helps engineers assess bearing capacity, settlementThe act of establishing a community in a new area., and slope stability, ensuring safe and efficient designs.

Soil

Eurocode 7 (EN 1997-1: Geotechnical Design – Part 1: General Rules) is specifically dedicated to geotechnical engineering, offering guidelines for soil testing, analysis, and design methodologies.

Soil is a natural, heterogeneous material composed of solids (minerals and organic matter), liquids (water), and gases (air). Its behaviour depends on several properties:

1. Grain Size Distribution (e.g., clay, silt, sand, gravel)
2. Consistency (plasticity and liquidity indices)
3. Density and Porosity
4. Shear Strength (cohesion and internal friction angle)
5. Permeability (water flow characteristics)

Soil classification systems organise soils based on particle size and plasticity. Common systems include:

• Unified Soil Classification System (USCS)
• British Soil Classification System (BSCS)

Eurocode 7 emphasises soil characterisationProblem-oriented approach where each emission or consumption of raw material is in a quantity that reflects the problem caused. through field and laboratory testing, such as sieve analysis, Atterberg limits, and in-situ density tests.