The Graphical representation of purpose specific geological information or data obtained from field (after site investigation) which can be quantified (in numbers), with reference to north at certain scale is known as Engineering Geological Map.It includes lithology (distribution of rock types), soil types (alluval,colluvial,residual etc.), geomorphology (river,stream,slope aspect ,inclination,slope instabilities like mass movements i.e, landslides,debris flow,slope failure etc.).
In others words,an engineering geological map is a type of geological map which provides a generalized representation of all those components of a geological environment of significance in landuse planning, and in design, construction and maintenance as applied to civil and mining engineering. Engineering Geological Maps are prepared on a scale of 1:10000 or smaller.
Classifications:
Engineering geological maps may be classified according to purpose, content and scale as follows:Show More
The Graphical representation of purpose specific geological information or data obtained from field (after site investigation) which can be quantified (in numbers), with reference to north at certain scale is known as Engineering Geological Map.It includes lithology (distribution of rock types), soil types (alluval,colluvial,residual etc.), geomorphology (river,stream,slope aspect ,inclination,slope instabilities like mass movements i.e, landslides,debris flow,slope failure etc.).
In others words,an engineering geological map is a type of geological map which provides a generalized representation of all those components of a geological environment of significance in landuse planning, and in design, construction and maintenance as applied to civil and mining engineering. Engineering Geological Maps are prepared on a scale of 1:10000 or smaller.
Classifications:
Engineering geological maps may be classified according to purpose, content and scale as follows:
According to Purpose:
According to purpose, they may be classified as:
Special purpose:
Multipurpose:
.According to content:
According to content they may be classified as:
Analytical maps:
These maps provide details about the individual components of the area. For example, map of weathering grades, jointing map, seismic hazard map.
Comprehensive maps:
These maps depict all the principal components regarding geological information of the area only. These are of two kinds- maps of engineering geological conditions depicting all the principal components of the engineering geological environment; and maps of engineering geological zoning, evaluating and classifying individual territorial units on the basis of the uniformity of their engineering geological conditions.
Auxiliary maps:
Complementary maps:
These include geological, tectonic, geomorphological, pedological, geophysical and hydrogeological maps. They are maps of basic data which are sometimes included with the set of engineering geological maps.
According to scale:
According to scale they may be classified as:
Large-scale: 1 : 10000 and greater.
Medium-scale: less than 1 : 10000 and greater than 1 : 100000.
Small-scale : 1 : 100000 and less.
Geological features represented on engineering geological maps:
The character of the rocks and soils, including their distribution, stratigraphical and structural arrangement, age, genesis, lithology, physical state, and their physical and mechanical properties.
Hydrogeological conditions, including the distribution of water-bearing soils and rocks, zones of saturated open discontinuities, depth to water table and its range of fluctuation, regions of confined water and piezometric levels, storage coefficients, direction of flow; springs, rivers, lakes and the limits and occurrence interval of flooding; pH, salinity, corrosiveness.
Geomorphological conditions, including surface topography and important elements of the landscape.
Geodynamic phenomena, including erosion and deposition, aeolian phenomena, permafrost, slope movements, formation of karstic conditions, suffusion, subsidence, volume changes in soil, data on seismic phenomena including active faults, current regional tectonic movements, and volcanic activity.
Engineering geological map should fulfil the following requirements:
It should portray the objective information necessary to evaluate the engineering geological features involved in regional planning, in the selection of both a site and the most suitable method of construction, and in mining.
It should make it possible to foresee the changes in the geological situation likely to be brought about by a proposed undertaking and to suggest any necessary preventive measures.
It should present information in such a way that it is easily understood by professional users who may not be geologists.
Preparations:
All the geological features (rock units, bedding planes, faults, foliations, etc.) present in the area must be shown so that the geology of the area can easily be underestood and interpreted.
Rocks units or geologic strata are shown by appropriate and relevant color or symbols to indicate where they are exposed at the surface.
Bedding planes and structural features such as folds, faults, foliations, and lineation are shown with the strike and dip or trend and plunge symbols which give these features three dimensional orientations.
Stratiographic contour lines can be used to illustrate the surface of a selected stratum illustrating the subsurface topographic trends of the strata.
Orientations of planes are often measured as a strike and dip while of lines are shown as trend and plunge.Strike and dip symbols consists of a long strike line, which is perpendicular to the direction of a greatest slope along the surface of the bed, and a shorter dip line on side of the strike line where the bed is going downwards.The angle that the bed makes with the horizontal, along the dip direction, is written next to the dip line.In azimuthal system, the orientation is shown as strike / dip.
Trend and Plunge are used for linear features and their symbol is a single arrow on the map.The arrow is oriented in the down going direction of the feature (Trend) and at the end of the arrow, the number of degrees the feature lies below the horizontal (Plunge) is noted.eg- 34/86 indicates a feature that is angled at 34 degrees below the horizontal at an angle that is just East of true South.
Uses of Engineering Geological Maps:
These provides the information about the rock mass and soil type available in a particular area which can be used for site selection.
These helps to find the possible and probable reserve and estimate the reserve capacity.
These helps to access the environmental effect.
These helps to analyse and find the slope stability strength of the rock mass, soil, etc.
Uses of Topographical Maps:
From a given contour plan, the section along any given direction can be drawn to know the topography of the area.
A contour plan helps in section of route of highway, canal, etc.
It helps to calculate the capacity of the reservoir.
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