Volume of multiple subsurface layers

[Anonymous]

I have recreated a corridor from Tender data for pricing a project. One of the items that has been requested from me is the volume of the different layers of material to be removed so that we can properly balance the cut and fill or be aware of the need to import/export material.

To simplify things I have condensed the TP and BH data into 3 layers. Topsoil, acceptable fill material (mostly sandy clays with cobles) and rock. The topsoil will not be used as fill material, only the other 2 layers. I have created a surface for existing ground level, a surface for top of fill material (using a volume surface between existing ground and depth to acceptable fill material), and a surface for top of rock (using volume surface between existing ground and depth to rock). So now on my profile I have 3 surface profiles for the different material. Looks good.

My issue now is how to calculate the volumes of the 3 materials. What is the best way to do this. If I create a corridor with daylight to EG I can get overall cut and fill to existing ground. Do I now also need to create corridors with daylight to the other materials, disregard the fill and take the cut areas away from each other? Will I instead do this with volume surfaces in some way? Is it best to use materials and sample lines (my experience with this side of things is lacking)? I just want the quickest way that will give a good approximation as I need to have this in by the end of the week. I also have a feeling there will be a few more of these coming up so I really need to learn how to do this properly.

Thanks in advance for any help in this area.

[tcorey]

I would do it with volume surfaces. Let's say you have surfaces: Top, Middle, Bottom.

Make one vol surface that compares Top to Middle. That's the volume of Top.

Make another vol surface that compares Middle to Bottom. That's the volume of Middle.

That's the simple way, but, yes, you could do it with corridors.

[M_c3d]

If you have included the correct road build up in the assemblies (or go back and change it), then you can extract a surface for the top of each layer of construction and calculate the volumes. If you go to corridor > surface tab > and when creating the surface specify each code that you want, i.e. instead of top say pave 1 etc. This will tie in with your assembly build up.

For your daylight, I would do this as a separate surface with boundaries to calculate the volume required outwith your road to tie into existing.

Hope that makes sense.

[Anonymous]

Thanks for the reply tcorey.

But would your answer give me the amount of fill too?

Surely I need to trim the surfaces to the corridor first in some way so that I am only comparing the different surfaces within the corridor. Or am I misunderstanding your answer.

Was thinking of just creating 3 corridors on top of each other with each daylighting to a different surface then somehow use volume surfaces between the 3 corridor surfaces. Would this be right? Probably be trying this with the first of many alignments this afternoon.

Regards,

Peter

[M_c3d]

I would say that its dangerous to calculate volumes to that minute detail. They will only be as accurate as the topo survey and the skill of the user creating the corridors (no offence meant).

[M_c3d]

The way I do cut & fills is to;

1. model the existing ground surface
2. model the top soil strip surface
3. model the proposed ground
4. model formation level of the proposed ground
5. Do a cut & fill analysis of the top soil strip vs formation level to give cut & fill

the road construction is then standard construction on top of this

[Anonymous]

Thanks for your response mmcgovern,

The road construction itself is not really an issue. These are forest tracks with just 300 stone on them. Volume of this is easy to calculate by alignment length and width for all alignments. It's just the amount of cut of the existing ground materials that I'm after as the topsoil wont be used as fill material so a general cut/fill volume from a corridor may look balanced but obviously it's not as I'm going to be requiring more fill material to replace the topsoil. The topsoil itself will just be placed on the cut/fill batters for planting after construction.

Regards,

Peter

[M_c3d]

In that case I would just do a volume based on proposed formation level versus top soil strip

[Anonymous]

mmcgovern,

Your last post I think is the way I will be approaching this.

I agree that the results are only as good as the quality of the user, the SI data, the topo etc. Any result that I get will only be general I know.

I was asked to do it and so I will try......

regards,

Peter

[M_c3d]

Higher ups can wish the software can work miracles, but it really can't...

[Anonymous]

mmcgovern,

I think those higher up think the software works all by itself and I just know which buttons to press!! If only life was that easy......

[Anonymous]

Update for you here.

I ended up doing this with Material Take-off instead. I didn't realise at the time that you could also get material quantities for subsoil layers. Only ever used it for quantities of road construction materials. This means that I can overlay a mass haul profile onto my design profile and see which areas will have the biggest impact on balancing the cut/fill. As I'm using the EW to the subsoil layer it means I am able to disregard the topsoil for the balancing exercise and then just add it back in at the end for pricing. It's a shame that the total volume tables don't give a total volume for each material though instead of having to read the last value off the material tables.

Regards,

Peter