Environmental Engineering Reference
In-Depth Information
5.4.2.2
Geotechnical mapping
Geotechnical mapping at and near the sites of the proposed works is the key to the success
of the site investigation. The mapping involves the identification and location of all surface
features relevant to the establishment of geotechnical models at the sites. The plans and sec-
tions produced by the mapping form the initial geotechnical models which are the basis for
the subsurface exploratory work, aimed at checking the models, filling in gaps and answer-
ing specific questions raised by the indicated geological environments (see Chapters 3 and 4).
The geotechnical maps are usually produced at an intermediate scale (1 : 5000 or 1 : 2500)
covering the general works sites, and at 1:1000 or 1:500 covering the immediate area of the
sites. The maps show the following types of factual information as shown on Figure 5.6.
-ground surface contours;
- geomorphic features, e.g. slope changes, areas of hummocky ground;
- geological surface features, e.g. areas of rock outcrops, scree, boulders and soil;
- features of
in situ
rock, e.g. rock types and their boundaries, attitudes of bedding and
foliation, the nature, location and orientation of important geological defects such as
sheared or crushed zones;
-groundwater features, e.g. springs, seepage, areas of swamp and vegetation indicating
moist or wet ground;
Figure 5.6.
Plan showing some of the features presented on a large scale geotechnical plan of a site for
an embankment dam.
