Agriculture Reference
In-Depth Information
through the earthwork volume and vertical surfaces associated with Digital Terrain
Model (DTM) volumes. Horizontal areas usually refer to the area extent of the exca-
vation and horizontal areas enclosed by contour elevation lines. These areas are
defined by a series of discreet points along their boundaries. Areas are calculated
by connecting these points in a series of continuous triangles that extend across the
area. Given the northing and easting of each of the three vertices of each triangle,
and the lengths of each of the three sides of the triangles, each triangle's area can be
calculated as follows:
s ( s
A
=
a )( s
b )( s
c )
(6.1)
where
the area of the triangular area (m 2 )
a , b , c ,
A
=
=
the lengths of the three sides of the triangle (m)
s
=
( a + b + c )/2
There are several ways of calculating earth and soil volumes.
Depth Area Method
Depth Area Method (DAM) is the simplest method. In this method, volume of soil
is obtained by multiplying the thickness of the strata to be excavated by the surface
area of the strata. This can be done with reasonable accuracy only for strata that
is consistently thick and whose area extent is known. It is perfectly suitable for
estimating the amount of topsoil to be stripped at a consistent depth (usually 15 cm).
It is also applicable for estimating the volume of regular (square or rectangular with
vertical sideslopes) excavations of a consistent depth below a relatively flat surface.
Volumes are calculated as follows:
V
=
T
×
A
(6.2)
where
volume (m 3 )
V
=
surficial slope area (m 2 )
A
=
T
=
thickness of strata or even cut (m)
Total volume, V T = V i
Grid Method
The Grid Method extends DAM to an excavation of varying depths. The excavation
volume is obtained by applying a grid to the excavation area. The grids can be staked
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