Geotechnical Engineering

Disturbed soil sample is one in which the structure of the soil has been changed sufficiently that tests of the structural properties of the soil will not be representatives of in-situ conditions, and only properties of soil grains can be accurately determined.

Undisturbed soil sample is one where the condition of the soil in the sample is close enough to the conditions of the soil in in-situ to allow tests of structural properties of the soil to be used to approximate the properties of the soil in-situ.

Rock outcrops are defined as visible exposures of bedrock or other geologic formations at the surface of the Earth. Rock outcrops take many different forms within the Park, ranging from the massive granite boulders of Old Rag Mountain, to the sheer cliffs of Little Stony Man, and the jumbled boulder fields of Blackrock.

Most civil engineering projects involve some excavation of soils and rocks, or involve loading the Earth by building on it. In some cases, the excavated rocks may be used as constructional material, and in others, rocks may form a major part of the finished product, such as a motorway cutting or the site f or a reservoir. The feasibility, the planning and design, the construction and costing, and the safety of a project may depend critically on the geological conditions where the construction will take place. This is especially the case in extended ‘greenfield’ sites, where the area affected by the project stretches for kilometres, across comparatively undeveloped ground. Examples include the Channel Tunnel project and the construction of motorways. In a section of the M9 motorway linking Edinburgh and Stirling that crosses abandoned oil-shale workings, realignment of the road, on the advice of government geologists, led to a substantial saving. In modest projects, or in those involving the redevelopment of a limited site, the demands on the geological knowledge of the engineer or the need for geological advice will be less, but are never negligible. Site investigation by boring and by testing samples may be an adequate preliminary to construction in such cases.

Abutment in bridge is designed as earth pressure and rest condition because abutments support the ends of the bridge and transfer the loads from the superstructure in to the ground. The abutments also support the bearing devices and the backwalls Moreover, bridge abutments connect the deck, or surface of the bridge, to the ground and help support its weight both horizontally and vertically. On short bridges, one abutment is placed at either end of the bridge and connected to the embankment, sometimes including a retaining wall.