Roads and railways

Prepared By – Ghanshyam Prajapati

• Roads and Railways are very important projects for any
countries and an index of its development.
• Such investigations are aimed at providing full details
regarding:
• Topography of the area
• Lithological characters of rocks
• Structural features of rocks
• Ground water conditions

• Topography is a field of geoscience and planetary
science comprising the study of surface shape and
features of the Earth.
• It is a map that shows and elevation field, meaning how
high and low the ground is in relation to sea level.
• A topographic map, also known as a
contour map, is a map that shows the
shape of the land using contour line.
• It is an important factor that controls
the selection of alignment of a roads
or highway project.

• An objective of topography is to determine the position of
any feature or more generally any point in terms of both a
horizontal coordinate system such as latitude, longitude,
and altitude. Identifying (naming) features, and
recognizing typical landform patterns are also part of the
field.
• A topographic study may be made for a variety of
reasons: military planning and geological exploration
have been primary motivators to start survey programs,
but detailed information about terrain and surface
features is essential for the planning and construction of
any major civil engineering, public works, or reclamation
projects.

Direct survey
• Surveying helps determine accurately the terrestrial
or three-dimensional space position of points and the
distances and angles between them using leveling
instruments such as theodolites, dumpy
levels and clinometers.

• Remote sensing is a general term for geodata collection
at a distance from the subject area.
• Remote sensing is the acquisition of information about
an object or phenomenon without making physical
contact with the object and thus in contrast to in
situ observation.

aerial and satellite imagery can be used to identify and
delineate terrain features and more general land-cover
features

• photogrammetry is a measurement technique for which
the co-ordinates of the points in 3D of an object are
determined by the measurements made in
two photographic images(or more) taken starting from
different positions, usually from different passes of an
aerial photography flight.

• Satellite radar mapping is one of the major techniques of
generating Digital Elevation Models (see below). Similar
techniques are applied in bathymetric surveys
using sonar to determine the terrain of the ocean floor.

• Geological surveys should provide all possible details
regarding the composition ,texture , structure and origin
of rocks.
• The ground may be divided into two parts-
• Consolidated rocks
• Unconsolidated rocks

• The consolidated rocks consist of igneous, sedimentary,
and metamorphic rock.
• Igneous rock is formed through the cooling and
solidification of magma or lava.
Granite

• Sedimentary rocks are types of rock that are formed by
the deposition of material at the Earth's surface and
within bodies of water.
• Examples:-
• Sandstones Quartzite

• Metamorphic rocks arise from the transformation of
existing rock types, in a process called metamorphism,
which means "change in form". The original rock is
subjected to heat (temperatures greater than 150 to 200
°C) and pressure (1500 bars).
• Examples:-
• Gneisses, Schits

• In stratigraphy, bedrock is consolidated rock underlying
the surface of a terrestrial planet, usually the Earth.
Above the bedrock is usually an area of broken and
weathered unconsolidated rock in the basal subsoil.

• The important structural features of rocks are given
below
1. Dip and Strike
2. Joints
3. Faults

• Strike and dip refer to the orientation or attitude of
a geologic feature. The strike line of a bed, fault, or other
planar feature, is a line representing the intersection of
that feature with a horizontal plane.
• The dip gives the steepest angle of descent of a tilted
bed or feature relative to a horizontal plane.

• When the cut is made in the direction of dip of beds, the
cut slope will have horizontal beds , and it will be the
same on either side.
• Hence in such case , there is a little dangers of slippage.
• This condition is quite safe and preferable.

• When a cut is made to the strike of beds , many
complications do arise , firstly the strata plunge steeply
across the cutting and secondly the slope of cutting is un
equal on sides.
• In some cases where layers
dip into the hills rather than
in the road, the cut is
considered quite stable.

• Joints influence the stability of the road cut in the same
manner
as the bedding planes.
• Moreover, even the hardest rock becomes weak by the
presence of enormous joints in its body.
• If the major sets of joints are prominently inclined towards
the free side of the cut , the danger of slippage of the
blocks is always imminent.

• Groundwater is the water located beneath the earth's
surface in soil pore spaces and in the fractures of rock
formations.
• A unit of rock or an unconsolidated deposit is called
an aquifer when it can yield a usable quantity of water.

• The ground water in many cases can reduce the bearing
capacity of the foundation soil.
• Swelling of the clayey soils under the influence of the
capillary ground water causes still worst troubles,
resulting in the formation of unevenness in the road
surface.
• The ground water conditions of the area will also need to
be investigated along the proposed alignment of the
roadway and railway.
• This include determining the position of ground water
table as well as water bearing properties of the various
rocks occuring along proposed route

Roads and railways

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