Geotechnical Engineering is the branch of civil engineering concerned with the engineering behavior of earth materials. It uses principles of soil mechanics, rock mechanics and engineering geology to investigate subsurface conditions and materials, determine the relevant physical/mechanical and chemical properties of the materials, evaluate stability of natural slopes and man-made soil deposits, access risks posed by site conditions, design earthworks and structure foundations and monitor site conditions, earthwork and foundation construction.
Geotechnical investigations are important in that they provide a deep understanding of both the properties and behavior of soil and rock and the interaction between them and the structures they support. The investigations entail fieldwork whose purpose is to examine and collect material samples -both soil and rock- that are then taken to a laboratory for further testing. The samples are obtained from the subsurface by means of different methods depending on the nature of the material.
Soft unconsolidated materials can be obtained by excavation of pits either by hand or by use of an excavator. During the excavation process, the materials are examined and samples collected at different depths depending on the change of properties. The samples are then stored in sample bags and labelled accordingly.
Hard consolidated materials i.e rocks are obtained through drilling by use of a drilling rig. The drilling methods differ depending on the purpose of the investigation although the most common and recommended method is core drilling method.
Below are some of the laboratory tests performed on the samples collected in the field;
The results obtained from the above tests are collectively analyzed to help come up with the suitable design that meets a project’s objectives.