Geology For Civil Engineers
Geology For Civil Engineers
Geology For Civil Engineers
Objectives:
projects for the purpose of assuring that the geological factors regarding the
highlights the various aspects related to dams, locations of dams, alignment of dams,
Introduction:
“The dams are barrier constructed across rivers to store water”. It will retain water
They are mainly built to control floods, for irrigating lands, for supplying water to
“The mass of water stored at upstream side of the dam is called as reservoir”
Heel of dam: is the contact with the ground on the upstream side.
Abutments: are the sides of the valley on which the structure of the dam rests.
Galleries: are small rooms like structure lift within the dam for checking operations.
Parapet Wall: low protective walls on the either side of the roadway on the crest.
Crest: The top of the dam. In some cases this provides a roadway or walkway.
Dead storage level(DSL): level of permanent storage below which water will not be
withdrawn.
Sluice way: These are the opening within the dam structures near base of the dam.
Sluice way structures are used to analyze and clear the slit accumulation in the
INVESTIAGTIONS:
6. Communication investigation
1. Majority of the portion of dam construction site should be on the high ground.
5. Dam site should be connected with the nearby towns and cities via road.
6. Dam site should have suitable topography that can naturally hold large amount of
LOCATION
1. Dams on shales: shales are two types: cementation shale and Compaction shales.
4. Dams on faults
Alignment
1. Abutment problems: The rocks that exist in the abutments of an dam should be
2. Dams on strata dipping Upstream: They are most capable of supporting the
weight of the dams and the pressure of the reservoir because the resultant of
these two forces acts nearly at right angles to the bedding planes of rocks.
INFLUENCE OF ROCK TYPES
The rocks present in the foundation and abutments of dam, must be sound
enough to withstand the expected static and dynamic pressures. For that the type
of rock present at the dam site plays most important role along with structures of
the rocks.
Igneous Rock: The massive igneous rocks like Granites, diorites, gabbros,
dolerites are excellent category because they posses high compressive strength,
shear strength and module elasticity required for very high dams.
But he extrusive igneous rocks like basalt are not desirable because they are
often vesicular.
Sedimentary Rock:
The strength of the sediments such as sandstone, conglomerates, and breccia will
If the degree of cementation goes increasing with time, the strength of sediments
increases.
For example:
The well cemented Cuddapah, sandstones and quartzite have high strength while
the much younger Himalaya sediments of Paleozoic and Mesozoic age are softer
and weaker.
Metamorphic rocks:
This group of rocks shows greatest variations in terms of suitability for dam sites.
Some varieties are hard, compact, thoroughly crystalline, well knit and massive and ideal
However, some other varieties like schists, slates and phylites may pose considerable
troubles and require very detail investigation with regards to their foliation, mica content,
1. Rocks of reservoir site should hard and impervious in nature like basalt, granite,
quartzite etc.
2. Reservoir should not be located in the areas composed of rocks having high porosity
3. The high density of fracture and joints within the reservoir rocks can seriously damage
4. To minimize the length and construction cost of the dam, narrow opening of the basin is
essential.
6. The general topography of the area should be capable of naturally holding large
7. The source of water in the reservoir should not be near from the tributaries that carry
8. Reservoir area should not contain mines or rocks with high salt content.
9. Availability of all types of construction materials near the site and near by town or city.
Conclusion
In ancient times, dams were built for the single purpose of water supply or
irrigation. As civilization developed, there was a great need for water supply,
irrigation, flood control, navigation, water quality, sediment control and energy.
Therefore, dams are constructed for a specific purpose such as water supply, flood
The demand of water is steadily increasing throughout the world. There is no life on
the earth without water, our most important resource apart from air and land.
For almost 5000 years dams have served to ensure an adequate supply of water by
storing water in times of surplus and releasing it in times of scarcity, thus also
Most of the dams are single purpose dams, but there is now a growing number of
multipurpose dams.
If the dams are not properly constructed, there will be severe disaster in the
downstream regions of dams. This unit highlighted the different general aspects of
dams, their causes of failure and geological structures affecting dam site, suitable