Tool 1 - Pad Template
Tool 2 - Draw 3D Polyline
Tool 3 - Offset 3D Polyline
Tool 4 - Join Nearest
Tool 5 - Bench Pond
Tool 6 - Valley Pond
Tool 7 - 3D Polyline by Slope on Surface
Tool 8 - 2D to 3D Polyline by Surface Model
Tool 9 - Input-Edit Profile
Tool 10 - Profile to 3D Polyline
Tool 11 - Design Template
Tool 12 - Break 3D Polyline by Surface Model
I. Pad Template (Tools 1-4)
A. 2D Polyline Closed Perimeter
The most basic use of a pad
template is for the creation of
flat-bottomed pits and flat "building pads", at any desired elevation.
The procedure is simply to draw a closed
polyline at 0 elevation, then select Design
Pad Template, found in the Grading pulldown menu, and enter
the side slopes and pad elevation. See the two polyline examples shown
here.
This piece of the larger drawing was carved out by first doing the
Rectang command, and making a
rectangular polyline as shown above. Then we did Break by Crossing
Polyline, under the Edit pulldown, using
default answers, followed by Write
Block, to write out the separate drawing.
The two polylines are drawn by
the Rectang command for the
pit, and the PL command at 0 elevation for
the pad.
B. Draw 3D Polyline
This is an obvious tool for creating
terrains. We recommend use of Carlson's
3D Polyline, found near the
top of the Draw pulldown menu. Our first
exercise is to build a ramp from north to
south into the pit. We will "arbitrarily" start at elevation 1978 by
"snapping" to the 1978 contour with the
"nea" snap (nearest), then snap to the base of the pit at 1950 with the
nearest snap. Then we will offset this
3D Polyline, connect its ends by Join
Nearest, and do a pad template at
2:1 sideslopes. As an exercise,
try Viewpoint 3D under the
View pulldown, and choose a SW viewing
angle at 35 degrees above the XY
plane to get a view similar to the 3D graphic shown. In this view,
erase the
original pad base polyline, which is still at 0 elevation.
This will prevent the "nea" snap from finding the 0 elevation base
polyline instead of the new, green,
pad polyline. Enter Plan at the command prompt, followed by two Enters,
to
go back to Plan View.
C. Offset 3D Polyline
After the 3D Polyline is drawn, do the Inquiry command Bearing & 3D
Distance, Linework
option, to check the percent slope of the 3D polyline. At
approximately 10% grade, it should be
"drivable" by haul trucks. Move the
second 3D Polyline to contact the base of pit.
D. Join Nearest
Now find Join Nearest, under
the Edit
pulldown menu. Select Directly
Connect Endpoints, and enter a 35 offset tolerance. Pick both 3D
polylines to
join them, as shown in the graphic.
E. 3D Polyline Closed Perimeter
Now we have a 3D polyline
closed perimeter, which can act as a pad.
Within the Design Pad Template
routine, we will no longer be asked for
a pad
elevation, since the program
will obtain the variable pad elevation from the vertices of the 3D
polyline. It is advisable to first do a
List command, under Inquiry,
to verify that each pad vertex is
non-zero.
The 2:1 cut side slopes (fill
sideslope is irrelevant, since we are in cut) leads to the drawing
shown in the graphic.
Note that we are consistently using Design Pad Template to trim existing contours and 3D polylines, and to not retain the trimmed portion. We are also consistently selecting not to draw contours. In this manner, we iterate our way to the desired final terrain. We should also note that we are using the standard 50x50 "number" of cells in the Pad Template routine, windowing the entire site each time. More cells or smaller dimensioned cells leads to a finer calculation.
F. One-Sided Pad Template
Design Pad Template also works with a 2D
or 3D polyline that is open and not closed.
In this case, the routine will ask for which side to offset (with a
closed polyline, it always offsets outward).
For example, suppose you were concerned where a pit located along the
northeast side of the site
would "catch" if it sloped at 2:1 from an elevation varying from 1980
at the north end to 1985 at the south end.
To put this 3D Polyline in, select 3D
Polyline under the Draw
pulldown menu, and choose
the prompt for elevation option. Enter the north elevation as 1980 and
the south elevation as 1985. Then
do Pad Template and choose the left side for the offset at 10:1.
The top of the cut did not impact the building pad or the parking
lot.
II. Bench Pond (Tool 5)
A. Fully "Incised" Pond
The Design Bench Pond routine
is
found
under the Grading pulldown menu. It is
based on the use of a closed polyline representing the top of the pond.
The program cuts a circular
pond into the existing terrain. Unlike Design Pad Template, the Design Bench Pond
routine
works "inward". The main thing
to remember is that if you have roughly 20 feet to the center of the
pond, and you want to go downward
at 2:1, do not ask for a depth greater than 10 feet. This will cause
one side to pass beyond the other, and
you will "hourglass" the interior. Another concept to remember is that
the program will cut downward
from the drawn polyline, which is placed at an elevation representing
the water level or top of pond. A
separate cut and fill ratio can be applied to the outside of the drawn
polyline. If you place the pond fully in cut
(fully incised), then one cut ratio would apply to the interior going
down to the base of pond, and another
would apply to the exterior going up to "daylight". Of course, the same
ratio can be entered for both slopes.
Here we have drawn a closed polyline in the lower right of the drawing,
and will set its elevation to the
lowest elevation the line crosses (as prompted by the program). This
will ensure that the pond is fully
incised and does not have any fill slopes.
B. Partial Fill-Partial Cut Bench Pond
A typical farm pond
might have the downhill side in fill and the
uphill side in cut. In fill, the flat-topped "bench" might be 10 feet.
In cut, the bench would disappear. Cut
above water into original ground might be 6:1. Cut below water might be
3:1. Fill could be set at 6:1 and 3:
below water. In this case, we would remove the top bench in
cut. The graphic shown is a bench pond cut into the
top center of the drawing at elevation 1994.
C. Revisit Pad Template by Doing a Diversion
Ditch
If you are getting the idea, try this on your own:
Draw a 3D Polyline that will drain the lower right pond into the upper
left pond. Do this through use of the 3D
Polyline
command, under Draw. Issue the command, and do a "nea" snap maybe
one-third down the northwest
"slope direction line" in the pond at the lower right of the graphic.
Connect with a "nea"
snap to a point halfway down the
southeast running "slope direction line" in the pond at the upper left
of
the graphic.
List your 3D polyline to be sure it runs downhill
from approximately 1992 to 1989, or thereabouts. We're after the
concept here. Then do Offset 3D
Polyline four
feet either way for base of ditch. Connect the ends up with Join
Nearest, tolerating 5' separation. Then do
Design Pad Template at 3:1
side slopes in Cut and Fill. Your result is shown
in 3D.
III. Valley Pond (Tools 6-10)
A. Constructing a Valley Dam
We
can "carve out" another
portion of our base map by first drawing
a "Rectang", and then using Break By
Crossing Polyline under the Edit
pulldown menu. We follow this
with Write Block, and write
out a new drawing called Valley1.dwg, seen in
the
graphic. Unlike Design Bench Pond,
the
Design Valley Pond routine
requires only a polyline axis line for the center
of the dam. The polyline can be a
2-point polyline, or it can have several vertices along its length to
create a concave or convex dam structure.
The main thing is to "overdraw" the axis polyline — make it ride up on
the left and right hillside, well
beyond the desired top of dam elevation. This allows the routine to
look inward and find the extents of the
dam on each hillside, without doing an artificial extension of the
polyline. Just "overdo" the length of the
axis line and you are in business. Another aspect to concentrate on is
the desirability to select enough
terrain upstream to enable the program to compute the full waterline
extents — the limits of the
dammed-up water. Without enough upstream terrain in the initial
selection set (which acts like a crossing selection),
you will not be able to compute the limits of the
water surface and the pond stage-storage information.
Our axis polyline runs from approximately 1960 on
one side of the valley to 1960 on the other. It crosses
the valley at 1931. Let's decide to put the top of dam
at 1950 even. We will make the dam 20' wide, with
3:1 downstream and 4:1 upstream slopes. Source of surface model is, as
always in this case study,
the screen.
B. 3D Polyline by Slope on Surface
How would you start at
the top of dam (elevation 1950) and build a
road running downhill at 6% grade? Or, in general, how would you obtain
3D polylines for roads and
diversion ditches that follow the terrain at prescribed grades starting
at desired points? The answer is 3D
Polyline by Slope on Surface (located in the 3D Data menu). This
routine requires that we make a grid
file for the terrain. Use the command Make
3D Grid File under the Surface pulldown menu, and select a 20x20
cell
dimension. Store the file as Dam.grd.
Then run the 3D Polyline by Slope on
Surface. Pick a starting point
on the north side of the dam. Facing downhill, you will go downhill to
the right. After the new 3D polyline
is drawn, offset it into the hill with the Offset 3D Polyline command,
then join the ends with Join Nearest,
then use Design Pad Template
to carve our road into the terrain. Follow that
procedure and you obtain the drawings shown here.
In the drawing showing text information at the upper left, we can see that we now have a "pad" for pad template. Because the southern side of the pad follows closed the original ground, it may "cantilever" over into the "air" in a few places based on the resolution of the calculation. It is recommended that the fill ratio used to catch the ground be low, such as 1:1 rather than 2:1, so that short cantilevered sections of the pad, if placed on natural 2:1 terrain, don't "skim" over the ground and create unnecessary fill. For the cut sections, we will use 3:1 to carve the road into the solid hillside. The result can be seen in 3D.
C. 2D to 3D Polyline by Surface Model
The 3D view above reveals a 3D polyline
running up the base of the stream channel in which the pond was built.
Such 3D polylines are important in
modeling accurate surfaces for pond design, pad templates and volumes
in general. For example, if you were
to triangulate and contour the valley at 1' interval (currently the
contours are at 4' interval), you would
obtain poor valley contours which "square off" in the valley — if you
did
not select the 3D Polyline "break line".
Thus, an important strategy — better yet, policy — is to dress up raw
contour maps with valley and
ridgeline 3D polylines that act as break lines, and restore the true
character of the terrain. The best way to make
these 3D polylines is to draw 2D polylines in drains and ridges (see
the three circled examples) and
"drape" them on the terrain. This is done by the 2D to 3D Polyline by
Surface Model command, found under the
3D Data pulldown menu.
D. Creative Uses of 2D to 3D Polyline by Surface
Model
More than a command to "dress up" contour
maps for greater modeling accuracy, the 2D to 3D Polyline by Surface
Model command (sometimes called the "drape" command) has
unexpected
uses. In the example, a
strata angling along a pit face creates instability in the upper part
of the pit. The goal is to "lay back" the pit
at 2:1 above the strata demarcation line, and retain the 1:1 slope
below
that line (which is drawn as a 2D
pline at the outset).
After the 3D Polyline is "draped" on the surface, you should use Change > Elevations, under Edit,
to
drop the entire 3D Polyline just a little, such as _0.2. This will
ensure it is fully in Cut. Then the Design
Pad
Template command can be used to perform a one-sided offset at
2:1 in
Cut, resulting in the drawing, shown here in
3D view.
E. Build a Diversion Ditch around the Dam Using Input-Edit
Profile and Profile to 3D
Polyline
With Osnaps turned off, draw a simple 2D
polyline ("PL" command or Carlson's "2DP") that starts on
the water side of the valley dam, and curves around the
hill to the south and into the drainage below the dam,
as shown in the graphic. The syntax for this using the
PL command is: pick first point, pick
second point to get a tangent (straight section) going, then type
A for arc, arc
it around the dam, then do L for line and a second L
for length, and pick a point that comes off tangent from the arc and
ends in the stream bed below the dam.
Then Enter to exit the PL command.
Now we are going to make this 2D polyline a 3D polyline with a
prescribed profile. To prepare for
this, we do Polyline Info,
under the Inquiry pulldown menu, and write
down the length of the polyline (this
will become the length of the profile we enter). This one here is 377.6
feet, which we will round up to 378.
We then use List Elevation,
under the Inquiry pulldown menu, and pick
on
the 3D polyline as close as
we can to the point where our 2D polyline makes contact. That elevation
is reported as 1929.4 (along
with all vertices elevations). We determine ahead of time that we want
the first 50 feet of the diversion
ditch to be a 1% downhill slope, starting at elevation 1946 (allowing 4
feet of freeboard to the top of the dam at 1950). We are ready for
Input-Edit Profile File, in
the Profile menu. We fill out the profile
dialog
as shown in the graphic.
The order of entry might be 0 and 1946 on the first line, 378
and 1929.4 on the third line, and 50 and slope% of _1 on the second
line, completing the profile. Save it, and
Quit from the dialog. The one
remaining step to get a 3D polyline is to select the command Profile to
3D Polyline, under the Profile pulldown menu.
Pick the ditch centerline and apply the newly saved profile to it.
Erase the old centerline and you obtain
a "yellow" colored 3D polyline centerline. Use the command Offset 3D
Polyline to offset the ditch into
the hill 8 feet for an 8' base (or offset 4' either way and erase the
original centerline). In either case, you
have two parallel 3D polylines. Now, do Join Nearest, tolerate 9' of
separation and Directly Connect Endpoints within Join Nearest.
(Note how 3D Polyline, Offset 3D
Polyline and Join Nearest
become a
familiar sequence in doing pad template work!). Now do Design Pad Template at
a cut slope of 1.5 to 1.
If it is apparent that the diversion ditch was initially drawn too far into the pond area and created fill, as seen in the graphic, then there is the option to re-design or simply to trim off the fill portion. This likewise applies to the portion of the diversion ditch at its terminus downstream. Note that gaps in contours that need to be re-closed can be very quickly fixed with Join Nearest. With the trimming completed, the final design appears in 3D.
F. Build a Curving Road from Top of Dam to Base of Pit using
Input-Edit Profile and Profile
to 3D
Polyline
Looking at the 3D view in the graphic, lets extend the road from the
top of
dam
into the base of the pit,
following a uniform grade and entering the pit at right angles on the
south side (or right-side, as seen in the graphic).
This "word problem" is nothing more than another iteration of
Input-Edit Profile File and Profile to 3D Polyline.
The first challenge is to draw the 2D polyline using the PL command.
We've already learned how to do this
and use the second L approach to come off tangent from an arc. We end
up with a centerline that might
look like the one in the graphic.
Just as before, find the length of the polyline using Polyline Info,
under Inquiry. We know the profile: it
runs from 1950 (the top of dam) down to 1930 in the
base of pit. So we go straight to Input-Edit
Profile File, perhaps name it Road (Road.pro) and put in
a simple two-entry profile as shown in the dialog
box display here.
The slope of the road at -3.17 percent is very acceptable for any
type of vehicle. So now
we choose Profile to 3D Polyline, and
apply
Road.pro to the road centerline. This time we will
offset the new 3D polyline 10 feet either side using
3D Polyline Offset, and erase the original middle centerline (or render
it harmless
for terrain modeling by the command 3D
Entity to 2D under Edit). This
raises
an important point: when we select entities from the screen using
Design Pad
Template, Design Valley Pond and
Design Bench Pond, the pad or
pond
polyline itself
is filtered out
of the selection set, and it is not used for modeling the original
surface.
If we
left intact a 3D polyline centerline that was not part of our pad, it
would skew
the surface model badly. Thus, if we offset left and right for the
outside of
the road, the middle of the road must go, must be erased, unless we
chose
the "grid file" option for the original surface. After offsetting 10'
either side and erasing the center 3D polyline, we Join Nearest at a
21' tolerance. Then we do Design Pad
Template at standard 2:1 slopes.
Here is
the final 3D view. (You might use Design
Pad Template to divert the ditch and
not flood the pit!).
IV. Pad Template in Combination with Design Template for Roads, Ditches, and Levees (Tools 6-10)
A. Roads with Ditches and Berms
The limitation of Offset 3D
Polyline within Pad Template is that
roads cannot easily be given dynamic characteristics: They won't
automatically carve in ditches in cut, or
build a berm in fill where fill exceeds a certain threshold, for
example. Since these "intelligent" features
exist within the Design Template
routine in the Roads menu of the Civil Design module,
all we need to do is invoke
the "template" option within the Pad Template. Pad Template will then
go out and get a Design Template
and apply it to the one-sided or closed pad perimeter. To illustrate
this, let's first make a centerline that
will have cut and fill. Consider the centerline drawn in the graphic.
If we go a uniform grade from the existing road, upward to the
ending
elevation (which might represent a
mining bench), we are "bound" to get cut as we cross
the lower point and fill as we cross the second drain.
To "guarantee" fill, we will go uphill early and
lessen the last portion of the grade, using a vertical
curve length of 500 between profile grades. This is
another exercise of Polyline Info (for length), verifying
start and end grades, and Input-Edit Profile (as shown
in the dialog).
With the profile input (named road1.pro), we
can select Profile to 3D Polyline
and turn yet another
2D polyline into a 3D polyline. The difference now
is that we will not offset the 3D polyline to create a closed, looping
"pad". We will instead use a template
made in Design Template, and
apply it to the 3D polyline.
B. Entering a Template in Design
Template
Design Template, located under
the Roads menu
in the Civil Design module, is icon driven. See this horizontal strip
of icon options.
Shown here is a
selection
of dialogs that illustrate our entry of a 24' wide road (12' either
side) at 2% slope, no shoulder, no subgrade, a 3:1 slope for 6' to the
base of ditch, a conditional cut upslope, a 3:1 slope in fill, but a
2:1
berm in fill, rising 4 feet, used when fill exceeds 5 feet. To begin
with, this small dialog appears when the Grades button, within the
Design Template dialog box, is clicked.
Note that when you are putting in a ditch, you need to click
"Start" at the lower-left of the Cut Grades dialog. The conditional cut
upslopes
mean 4:1 up to 4 feet of fill, 3:1
between 4 and 10 feet of fill and 2:1 above 10 feet of fill.
The "typical section" can be drawn using the command Draw Typical Template under Roads. This will help you verify the quality of your template. Our template is shown here.
C. Design Pad Template
Now let's use the Design Pad Template
routine, found in the Grading menu.
The dialog box for Design Pad
Template is filled out as shown.
For the first time, we have selected the "template" option under
Design Slope Format. The program
will prompt for a cross section interval. Let's use 20. Finally, here
is how the road appears in 3D using
the command View (menu) > Viewpoint
3D.