Volume Calculation for Landslide

[Anonymous]

I really need help here. How do you calculate the volume of a landslide? I've searched all internet to find a topic about landslide volume calculation in Civil 3D and haven't found someone who can explain it in plain and easy to understand way. I have attached a Topo of a landslide with all the information inside the CAD file. Also an image of how landslide looks like. If someone can explain step-by-step, the standard approach to find the volume, would be greatly appreciated. I can provide you with more info if needed. 

[Anonymous]

It has been a while since i've done something like this. 

Essentially you need 2 surfaces:

-surface prior to landslide

-surveyed landslide surface

I believe there are a few different ways to calculate volume. I believe you can paste one surface into another, to create a "combined" new surface and then look for volume differences between those surfaces. 

I'm trying to recall from 2 years ago working on a landslide in Utah. 

[tmachado]

Hi @Anonymous, Becuase you don't have existing condition information (surface) prior the landslide, I calculated the volume based on your proposed elevations

So, I created a boundary to delimit the area of the landslide

Create a new surface with your proposed contour information and added the boundary of the landslide to the new surface.

Then created a Volume surface between EG and Prop

If you need the total volume should be Cut+Fill

Here is the file I used back, I worked on C3D 2018

[Anonymous]

Thank you man. Please try to recall and share your experience about landslide volume calculation. 

[Anonymous]

Thank you very much @tmachado for your nice reply. 

I believe the volume that you calculated did not consider the 10 feet depth and also the slope of excavation. I usually do the same method as you explained. But if you read the question inside the cad file, it asks for excavation of 10 feet below the existing ground (undisturbed area around the landslide) and it must have a slope of 2H to 1V inside to the landslide hole.

That is where I get confused. How to tell the surface that the hole that we are digging has a slope of 2H:1V from the proposed grade boundary. Sorry if I didn't explain it well in my initial post.

[tmachado · Accepted solution]

Ok @Anonymous, sorry I didn't read the info in the file my bad. So then you will need to use your grading tools to create the excavated surface, using the limit of earthwork (which I will totally recommend you to use a polyline instead of a splained line) create a feature line from it and assigned the elevation from your EG.

Grading to the inside of the feature line to a relative elevation of -10 with a slope of 2:1, then create infields to add the bottom of the surface and that will be your new excavation surface.

fo the Volume, create a volume surface with your proposed surface and the excavation surface.