How to represent a slope wrapping around an object

[Anonymous]

Hi everyone. I'm trying to model a concrete caisson for land reclamation purposes. The thing is I want to represent its backfill, which eventually wraps around the caisson and ends touching its front face. I've tried to recreate this using the grading tool, but have not been successful. I'm attaching a simple image of the caisson with the contact areas of the slope, which by the way, is equal along all of the faces.

I am not a native English speaker, so if you need any clarification on the issue, feel free to ask.

Thank you very much in advance!

[Neilw_05]

I used your dataset to recreate the technique I demonstrated earlier. Due to file size limitations I am not able to post my model. Also due to performance issues with C3D I am having difficulty producing a screen cast ( I really dislike this software).

The technique is the same as I showed earlier. It is difficult to explain but I'll try by using a screen capture.

Usinging the rectanlge on the uphill side of the caisson (Green), create a grading that targets the existing terrain. The grading should not wrap around the entire caisson. Instead it should start and end at the southwest and southeast corners of the rectangle so there is a gap across the downhill side of the caisson.. This will produce a grading that covers the north, east and west sides of the caisson. You will need to terminate the grading just slightly past the SE & SW corners so as to form the radial slope around the corners at the gap in the grading.

Next draw featurelines along the sides of the gap (Magenta) connecting the rectangle to the daylight line on the downhill side. These featurelines should have the same slope as the daylight grading. Lastly apply gradings to the 2 magenta featurelines that target the existing ground along the downhill face of the caisson, again using the same slope as the other gradings. My screen capture only shows the grading on the west side of the caisson.  

[Anonymous]

Thank you, Neil. I'm sorry, but it seems I'm doing something wrong and I can't get to reproduce your technique. I did the first grading and left the caisson's gap. The problem comes when doing the next feature line... Does it have to be in the same site as the first grading? Nevertheless, I am trying to grade from it but there's nothing going on after calculating: no slope, no feature lines, no surface...

Could you please explain step by step how you did this? At the end, is it one whole surface what you have as a result, or different surfaces?

Thank you and sorry for any inconvenience.

[Neilw_05]

Sorry, I'm having problems getting it to work. I'll see if I can do it using a different workflow and get back to you.

[Joe-Bouza]

note by hand the slope is steeper perp to the contours

[Neilw_05 · Accepted solution]

Here is a screencast showing the technique. It is my first attempt using the forum screencast software so it's pretty crude. There will be some awkward steps in the workflow when I fumbled for tools.

The technique is the sameI recommended earlier. You create a featureline around the caisson and apply the daylight grading to it.

1. Set grading parameters to: Site=pedraplen. Grading Group =Pedra1. Target surface=SB+Banqueta+cajones.

2. Start with a rectangular featureline around the caisson and set it to elevation 2.00.

3. Add a vertex at the approx. mid-point of the south (downhill) side of the rectangle and set it to the elev. -16.00 (=caisson base elevation)

4. Use the Insert High/Low elevation point tool in the grading tools to create elevation points that are 66.7% slope between the north corners of the  caisson along the south face. For the input parameters use -66.7% back slope and 0% ahead slope.

5. Apply a grading to the resulting featureline at 1.5 slope to the target surface.

6. Add an infill for the gap between the Caisson and the slope grading on the uphill side. 

Inthe video I start with a rectangle that includes the flat area on the north side of the caisson and I close the area with a featureline and add an infull. Other than that the procedure is the same. I realize thiis is hard to follow but it the bast I can do given the time I have spent on it. I hope you can make sense of it from the video.

http://autode.sk/1NU4KD6

[Anonymous]

Thank you for taking the time to do the screencast, Neil. Nevertheless, I see you've tackled the problem the same way as Joe did earlier in the thread. The problem with defining the grading from that feature line is that the grading is done perpendicularly to the FL, therefore you are left with those "jumps". Note the screenshot I attached in post nu. 40. There, you should see the ideal curvature of the slope around the caisson.

I might be asking for something impossible, I don't know! But thank you again for taking the time.

[Joe-Bouza]

Nice work. That looks remarkably similar to my results. 

Whats the slope perpendicular to the contours in the areas I highlighted. I could be wrong but it looks steeper than the rest. The OP and I went on about this and my post #45 pretty much proves it is a fact of life

[Neilw_05]

I was so focused on developing a technique for creating the grading that I didn't realize you were both addressing a different issue. The slopes are correct if measured perpendiculkar to the faces of the caisson. http://screencast.com/t/WrVYu3yS

I don't know how to make them correct if measured in any other direction aside from hand drawing the contours.

[Joe-Bouza]

Absolutely correct, and as my post # 44 shows, the same thing happens if you grade it by hand.

A slope in some direction has to give so as to not exceed the friction angle. The easy way out is to flatten the projection slope until the turn contour are 1.5:1.

A good reason not to max out the maximum slope. And the same in reverse fo min slopes

[Joe-Bouza]

Its not impossible: your design grade have to have some flexibility. Note: in the vicinity where the contours get steep it should be clear that if the daylight point was further away from the caisson, those slopes would approach your desired slope. 

A wing wall would put an end to the dilemma. I would consider a wall extending along the back side to the daylight point at both ends of the caisson. Then you can drop the grade on the sides and front so the friction angle will be honored

[Neilw_05 · Accepted solution]

I can get it close if I place small 1/4 circle arcs at the corners of the caisson and grade out from those. I'll throw it out there in case you want try to make it work.

http://screencast.com/t/PcazgexkRau

[Joe-Bouza]

I fell for it hook line and sinker.
As engineers we have to design by rules. Rule keep us and the public safe. And rule superced want

So what are the rules for this task:
1. Maximum slope =3:2
2. The constant slope around the caisson is a want
3. The constant slope around the caisson= 3:2 is a want.

As a designer we want 2&3 but are not ruled by them . We have 1 rule do not exceed 3:2

Get past that and the job is done

[Anonymous · Accepted solution]

OK, so let me explain what I did:

1. I graded from the uphill horizontal rectangle with a 3:2 slope leaving the caisson's gap.
2. I created two horizontal rectangles along the SW and SE corners of the caisson and graded again, but just sticking to the corner which defines the grading along the downhill face of the caisson. I am now left with two separate surfaces: the one from step 1 and another one which is comprised by the two downhill corners.
3. Created a new surface and pasted the latter ones.

The result is in the attached screenshot.

The process is a bit inefficient but more accurate towards measurements and presentations.

[Anonymous]

Correct Joe. Nothing against your arguments. I usually go for the practical approach, but, this time, I wanted to recreate the problem as it would look like in real life. It is nothing but an exercise. I appreciate your views and your collaboration.

The same goes for you Neil, thank you very much. That last approach with arcs looked interesting towards future exercises, who knows!

[Joe-Bouza]

Why does ther appear to be a gap between the caisson and the grading in model view?

[Anonymous]

Ok, here's another screenshot from another perspective.

Thank you

[Neilw_05]

Unfortunately there are no easy solutions to this problem that I can see at this time, but there are ways to get the job done as you have shown. I'm still playing with ideas on this one. It's a nice little exercise.

[Joe-Bouza]

@Neilw_05 & @Anonymous I have enjoyed this discussion.

The solutions are admirable academically, but we have to ask ourselves :can a D9 and an operator make it happen?