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Chapter 4 Working with Cross Sections
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Drawing Subgrade Surfaces for
Symmetrical Templates
Follow the general procedures for drawing a template surface, keeping in mind
the following points:
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With subgrade surfaces you draw only the top of the surface definition,
between the connection points. The rest of the subgrade surface information
is defined with the Define Template command.
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When drawing a subgrade surface for a symmetrical template, you start the
surface at the centerline (the vertical plane of the finished ground reference
point) and draw it to the left, tracing below the normal surfaces, if they exist,
and end the surface at the connection point.
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A template can only have one drawn subgrade surface and it must be below
all normal surfaces.
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To define multiple subgrade surfaces draw the one subgrade surface then
define the other subgrade surfaces as depths and grades when you use the
Define Template command.
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The side slope for the subgrade surface is determined by the slope settings in
Design Control when the template is applied to the cross sections.
Drawing Normal Surfaces for
Asymmetrical Templates
Follow the general procedures for drawing a template surface, keeping in mind
that when drawing normal surfaces for an asymmetrical template, you must
draw the entire surface. Start with the top of the surface at the centerline (the
vertical plane of the finished ground reference point) and draw to the left, in a
counter-clockwise direction until you return to the starting point. All normal
surfaces for the asymmetrical template must be drawn so that they close back to
their starting point.
Drawing Subgrade Surfaces for
Asymmetrical Templates
Follow the general procedures for drawing a template surface, keeping in mind
that with subgrade surfaces you only draw the top of the surface definition,
between the connection points. The rest of the subgrade surface information is
defined with the Define Template command. When drawing a subgrade surface
for an asymmetrical template, you start the surface at one of the connection
points and draw it, tracing below the normal surfaces, if any, to the other
connection point. You can start at either the left or the right connection point.
How Subgrade Surfaces Are Controlled
Subgrade surfaces are controlled by a set of rules that depend on the design
situation. In normal situations, the subgrade surfaces extend to the intersecting
ditch slope or match slope. If the subgrade does not intersect with either the
ditch slope or the design slope, it extends to the lowest point along the ditch
slope or design slope, and then ties into the ditch slope or design slope with a
vertical line.