Workflow for ongoing excavation

[neilyj666]

What would be the best workflow for calculating the volume of an ongoing excavation (in terms of model management).

I have an EGL and every week material is removed and the area that has changed is surveyed (with a little overlap). I wouldn't normally tackle this sort of thing in C3D due to my lack of knowledge of the most painless way to go about it (I'd use another package).

Is the best method to chop out the old area's breaklines/featurelines/3D polys etc (by xreffing the new stuff to see the changed areas), copying the new breaklines/featurelines/3Dpolys, then creating a new surface to compare with the EGL to get a cumulative volume difference OR is it easier to create an interim surface based on the new survey, and use hide/show boundaries and paste the interim to create the new excavation surface??

This workflow is dead easy in the software I would normally use - just paste the interim survey into the cumulative survey and any overlapping areas get removed leaving just the tail ends to join up - but I don't think this is possible in C3D

[wfberry]

Neil:

You have an EGL, I would assume this means an Existing Ground Line.  Perhaps it is an exisiting ground surface.

I would think you could decide on the complete boundary of the project and keep it consistent throughout the project's time span.

Guessing that you are usinig this for calculating periodic payments to the contractor.

I would think that precise calculations are not necessary at these intervals.

1. I would make a surface of the area that was recently changed.

2. Copy the EG surface and insert the above into it (FG1).  Compare the two surfaces.

3.  The next period make a new interim surface  and paste into a copy of FG1, now FG2.

Compare FG1 with FG2 (The surface names should probably be the ending period dates.)

Each time the comparison areas would always be the same.

That's what I would do.

Next?

Bill

[neilyj666]

EGL = Existing Ground Levels (points/breaklines and 3Dpolys) which makes the Existing Ground Surface

Would pasting in a survey that covers a small extent of a larger one remove all the existing information and replace with the new or would it just add it to the surface i.e. so you might have lots of spikes where the original data is still present andwhich creates horrendous editing problems??

[wfberry]

Well, am I assuming correctly that this is just for interim payments?  I am (was) thinking that precison is not necessary at these intervals.  If you placed a fairly tight boundary on the interim survey work I would thinik that this should work OK.

Apologies for the Level interpretation, I knew you were not over here.

Bill

[neilyj666]

No worries - I am on the correct side of the pond....!!!?!?!?

These are for interim calculations for a borrow pit/quarry but the surface has to be built correctly at the edges of the pit as it wiil be hazardous (and not permitted for health and safety reasons) to access the intermediate safety benches as the excavation progresses.

I have just done a quick experiment - if the interim is pasted into the ongoing excavation survey it does replace all the existing information so as long as the interim overlaps the ongoing by a few metres (to get common areas) the surface should build correctly. I assume though that this method would leave the original linework/breaklines etc in place as I am just working with the surface and that may get a bit confusing unless each interim survey's linework had an explicit layer assigned.

[wfberry]

As far as the ORIGINAL surface goes, you should not touch it since a copy is to be made.  Not sure about the interim frequency but if the drawing is getting large or too many surfaces, the SAVEAS sure can come in handy and start from there after you remove some surfaces.

I am somewhat surprised that we have not had any other ideas.

Bill

[neilyj666]

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@Anonymous wrote:

As far as the ORIGINAL surface goes, you should not touch it since a copy is to be made.  Not sure about the interim frequency but if the drawing is getting large or too many surfaces, the SAVEAS sure can come in handy and start from there after you remove some surfaces.

I am somewhat surprised that we have not had any other ideas.

Bill

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Me too...perhaps nobody actually uses it this way as it is such a potential PITA...

[sboon]

Not really that bad of a PITA - as long as you have a good workflow and project setup.

We do these sort of multi-phase quantity surveys quite often.  My process would go something like this:

• Start with a drawing that contains only the original EG surface and baseplan.  If you have a design surface then you will likely want a copy of that available also.  If the contractor overexcavates for some reason then your contract may not pay for that volume, and you'll need to account for it.
• The first set of quantity survey data should be processed in a new drawing, and a survey surface built there.  You'll likely want to xref the original baseplan in for reference, and you will need to dref in the EG surface.  Once you're happy with the survey surface then create an FG (after survey 1) surface, and paste the EG and the Survey surfaces into it.
• This final surface can be used for volume calcs, and will become the EG surface that you reference into the next survey drawing.
• When you start working in the next survey drawing you will be able to reference in the surface without the source data that it's built from.  This allows you to work without having to sort through point groups, or deal with overlapping breaklines etc.  Of course you can also xref in any of the older drawings if you need to check something from a previous session.

I've added some screenshots from a simple sample project.  This one shows the EG and the Pit design surfaces.

This is the first survey drawing, built from a single feature line.  The contractor didn't get much done this week.

Survey 2 indicates a lot more work done in the northeast part of the site.  You can also see that the surveyors did not provide enough data at the interface between this survey and the previous one.

Survey 3 includes work done in two separate areas of the site.  The contractor is getting close enough to grade that I would probably dref in the Pit Design surface here, and produce some sections or a grid of cut labels to make sure that they don't overexcavate the floor of the pit.  I can pretty much repeat this process indefinitely until the job is complete.

If anyone is interested in getting a copy of these drawings then PM me with your email address.

[neilyj666]

Thanks Steve - in summary then, your workflow is to build a surface from the survey data and then just concentrate on the surface and ensuring the final TIN looks right rather than adding/removing points breaklines/featurelines and building a surface from them??

In the software I normally use for this sort of work, I typically have the existing ground survey which never changes and make a copy of it. The first weekly/monthly measure survey data gets merged with the Existing ground to get a total excavation model (Period 1) which is compared with Existing ground to get the Period 1 volume. The Period 1 model is copied to Period 2 and the same process is gone through and cumulative volumes computed to existing ground. Cumulative Period 2 volume - Cumulative Period 1 volume = monthly volume.

[sboon]

It sounds like our processes are essentially the same Neil.

I've seen people try to combine all of the repeated surveys into a single file, and create many point groups and sites for the breaklines.  This method can work also but I found it to be very messy - you have to be very careful to avoid crossing breaklines etc.  The other issue with these type of projects is that it's always difficult for the surveyor to correctly tie in from the previous excavation to the boundary of the current work.  We often need to add a few points and do other edits to clean up the edges of the current survey.

[neilyj666]

Yes I've been working on some stuff today and am mainly using the surfaces, applying boundaries and pasting as required and it seems to be working ok - no crashes yet...

[onsionsi1]

Hello Mr. Steve,

I will be appreciate if you can send these DWG's to my email ( sadekcivil@gmail.com )

Also, thank you for your advice for this post.

Thak you.