Create slope perp to contours

[Balex]

How can I create a slope that gives a true slope perpendicular to the contour lines? e.g. specifying a 3:1 slope from a sloped baseline will give a 3:1slope perpendicular to the baseline alignment but the actual slope will be steeper than 3:1 as measured by the contours.

[Anonymous]

Hi,

The difference between your proposals to meet a theoretical maximum slope
and the methods proposed for a cross fall slope measured perpendicular to a
centreline reflect the difference in normal construction methods between
roads and earthworks.

Road designers have always computed and documented the cross-fall
perpendicular to the centreline, with a recognition that the actual maximum
slope may be slightly higher due to any longitudinal falls which may exist.
For example a 3:1 slope changes to 2.87:1 with a 10% longitudinal grade.

There is no warrant what-so-ever for abusing Autodesk for reflecting normal
road construction design and documentation practices in their software.

No matter how pedantic you may feel you can be in computing and documenting
different cross falls on a road cross section to allow that the maximum
slope will change with the change in grade of the road centreline, the
chances of finding a grader driver who will take any notice of the varying
cross fall labels on the plans is zero. The driver will set his blade to
the 3:1 and use that regardless of the longitudinal slope.

In the earthworks world your comments are spot on and reflect normal
construction practices. However, you should recognise that there are many
earthworks plans (and in particular car park plans where conventional labels
are for grades parallel to and perpendicular to the sides) with labels
showing grades on them in a particular direction which do not reflect the
maximum slope, but the slope in the direction of the arrow.

Where you are designing earthworks, starting from a sloping feature line and
the design rules are such that you must meet a specific uniform maximum
slope, then you need to recognise that the tools supplied by Autodesk (and
every other of the many road/earthwork design programs I've seen) are not
designed to do this and you as the designer have to follow the procedures
already outlined by ChristpherF.

From the viewpoint of a setout surveyor, if I was supplied with a set of
plans showing a surface line and was asked to setout the toe of a true 3:1
slope from that surface line - such process would involve computing and
measuring items not perpendicular to the baseline, I'd move on to another
job without bothering to tender for that one.

--

Laurie Comerford
CADApps
www.cadapps.com.au
www.civil3Dtools.com

wrote in message news:5435552@discussion.autodesk.com...
Standard engineering practice around here is: if i say "3:1 slope" on my
grading plan, it needs to be 3:1 measured perpendicular to the contours
(that's what a 3:1 slope is), and I note it as such with an arrow and rate
drawn along the fall line.
If the surveyors use a base line as a basis for their slope stakes, they
need to calc a rate at that station from the top to the toe based on my true
2:1 slope.

[Anonymous]

Laurie:

Keep this under your hat. I totally agree with you.



Bill

[Anonymous]

Ditto. 😉

--
John Mayo
Project Engineer
Conklin Associates
Ramsey, NJ

Civil 3D 2007, LDT 2007, Raster Design 2007
P-IV at 3.5 GHz
2 GB Ram
Nvidea Quadro FX w/ 128 MB Ram
"wfb" wrote in message
news:5435675@discussion.autodesk.com...
Laurie:

Keep this under your hat. I totally agree with you.



Bill

[Anonymous]

It's obvious that you have not been using the grading tools to any great effect. The grading tools do not use sections. You cannot adjust the slope to get the results you want like you can manipulating road sections. The grading tools used as they are on a hillside job would be a disaster. Even a commercial site would be in big trouble if you used the tools to produce a slope from the outer boundary to a pad. Your client proceeds to have a building designed based on that area from the toe of slope out and then when it come to staking the slope the surveyor sees 2:1 on the plan and uses it not knowing that the real slope on the plan is 1.9:1. The toe as staked now encroaches on the building. What do you do now!! Go to the City and explain to them that the software produced a 1.9:1 slope instead of 2:1 and beg them to give you some leeway. What if the UBC won't allow them to very the slope(or the soils engineer for that matter). This is an issue that came up in the grading tools provided in LDT and we stopped using it because it didn't work. We have been preparing plans for major hillside jobs and don't need the added risk of using a program that does not produce the results we need.

[Anonymous]

So you are saying that with a level pad grade and using a grading object
along the pad you cannot get a 4:1 slope using the grading tools at 4:1. At
least that is one your remarks, I think.

Bill

BTW, with name like jpatkwc, maybe Vanna would sell you another vowel.

wrote in message news:5435821@discussion.autodesk.com...
It's obvious that you have not been using the grading tools to any great
effect. The grading tools do not use sections. You cannot adjust the slope
to get the results you want like you can manipulating road sections. The
grading tools used as they are on a hillside job would be a disaster. Even
a commercial site would be in big trouble if you used the tools to produce a
slope from the outer boundary to a pad. Your client proceeds to have a
building designed based on that area from the toe of slope out and then when
it come to staking the slope the surveyor sees 2:1 on the plan and uses it
not knowing that the real slope on the plan is 1.9:1. The toe as staked now
encroaches on the building. What do you do now!! Go to the City and
explain to them that the software produced a 1.9:1 slope instead of 2:1 and
beg them to give you some leeway. What if the UBC won't allow them to very
the slope(or the soils engineer for that matter). This is an issue that
came up in the grading tools provided in LDT and we stopped using it because
it didn't work. We have been preparing plans for major hillside jobs and
don't need the added risk of using a program that does not produce the
results we need.

[Anonymous]

The grading tools work when you grade up or down from a level surface. They don't work (the slopes they convey are not what you entered in the criteria) when you grade from an irregular surface up or down to a level surface.

[Anonymous]

We're getting off track here. the issue is really whether the grading tools work as represented, and whether they are of any use in grading design. Road sections are 1 thing- grading design is another. It's hard to believe that anyone would expect that if you specify a 2:1 slope away from a grading object that you'd get something other than that, and hard to believe that software could be developed specifically for grading that works like that. There is no "theoretical maximum slope". A 2:1 slope is just that. I'm surprised that there is debate here. The slope rate through a section IS NOT the rate of the slope, and is of little use to me except as a drafting tool for cross sections. There is potential for disaster if a grading designer thinks he is creating a 2:1 slope (remember the UBC max.?) only to find out that his slope is shy and has to be REBUILT.
Again, this program is way wrong and of limited value as a grading design tool.

[Anonymous]

Hi,

The program does not do what you expect and you know it doesn't do what you
expect. You know how to use it so it does do what you expect thanks to
ChristopherF. So please just go ahead and use it that way, or write your
own software to meet your specific needs.

Meanwhile the rest of the world will continue to use the grading object to
meet their needs for creating design slopes along the line perpendicular to
the feature line as it is documented to do.

ps Could you point me to a reference to the meaning of "rate of slope". I
haven't seen that terminology before.

--

Laurie Comerford
CADApps
www.cadapps.com.au
www.civil3Dtools.com
wrote in message news:5436076@discussion.autodesk.com...
We're getting off track here. the issue is really whether the grading tools
work as represented, and whether they are of any use in grading design. Road
sections are 1 thing- grading design is another. It's hard to believe that
anyone would expect that if you specify a 2:1 slope away from a grading
object that you'd get something other than that, and hard to believe that
software could be developed specifically for grading that works like that.
There is no "theoretical maximum slope". A 2:1 slope is just that. I'm
surprised that there is debate here. The slope rate through a section IS NOT
the rate of the slope, and is of little use to me except as a drafting tool
for cross sections. There is potential for disaster if a grading designer
thinks he is creating a 2:1 slope (remember the UBC max.?) only to find out
that his slope is shy and has to be REBUILT.
Again, this program is way wrong and of limited value as a grading design
tool.

[Anonymous]

I think the horse is dead already. We've come to the conclusion that the
grading tools don't meet the design parameters for some people. Those same
paramters are acceptable for many others. We need not continue this thread
with minutiae.

What are the options?
1. Use other software or techniques that meet your needs.
2. Add your request to the wishlist. If enough people require that this be
changed it will happen. If not, then it may not. It's majority rules here.

Matt

[Civil3DReminders_com]

The UBC (1997) states as a definition "Slope is an inclined ground surface the inclination of which is expressed as a ratio of horizontal to vertical distance". The UBC does not specify how the slope is to be calculated, whether from a baseline or the maximum slope resulting from grading from a baseline. The program appears to meet the UBC definition of a slope unless I missed where it tells you how to measure the slope.

[steve.mccoy01]

Did you ever find a way to maintain a max slope perpendicular to the contours when the base line road slope varies?