FCE 311 GEOTECHNICAL ENGINEERING

2. INTRODUCTION TO SOIL MECHANICS

Department of Civil & Construction Engineering

University of Nairobi

2.1 Definition of Soil

 

• Soil is the relatively loose mass of mineral and organic materials and sediments found above the bedrock, which can be relatively easily broken down into its constituent mineral or organic particles.

Soil Layers• Soil consists of layers

of minerals constituents of variable thickness, which differ from the parent materials in the morphological, physical, chemical and mineralogical characteristics

2.2 Soil Mechanics and Geotechnical Engineering

Soil Mechanics

• Soil mechanics is a branch of engineering mechanics that describes the behaviour of soils. Soil mechanics provide the theoretical basis for analysis in geotechnical engineering

Geotechnical Engineering

• Branch of civil engineering concerned with the engineering behaviour of earth materials.

• Uses principles of soil mechanics, rock mechanics and engineering geology to investigate:

1.Subsurface conditions and materials,

2.Relevant physical/mechanical and chemical properties of the materials,

Geotechnical Engineering – cont’d

3. Evaluate stability of natural slopes and man-made soil deposits,

4. Access risks posed by site conditions,

5. Design earthworks and structure foundations and

6. Monitor site conditions, earthwork and foundation construction.

Typical geotechnical engineering project

• A typical geotechnical engineering project begins with a review of project needs to define the required material properties.

• Then follows a site investigation of soil, rock, fault distribution and bedrock properties on and below an area of interest to determine their engineering properties.

Typical geotechnical engineering project

• A geotechnical engineer then determines and designs the type of foundations, earthworks and pavement subgrades required for the intended man-made structures to be built.

• Foundations are designed and constructed for structures of various sizes such as high-rise buildings, bridges, medium to large commercial buildings, and smaller structures where the soil conditions do not allow code-based design.