AutoCAD Civil 3D

[#1]

Trying to calculate volumes via compute materials and referring to screenshot: Am I correct in thinking that the soft clay volume can only be calculated correctly if the earthworks slope is extended to the base of soft clays? 

[#2]

I am thinking the shape needs to close to compute the area then vol.

[#3]

In this case your material section is going to have a vertical face on the left side, from the toe of earthworks slope down to the base of the soft clay.

[#4]

How would you attempt to get this number Steve? I know a second corridor can be run along the daylight and extend down to the base but is there a way with one corridor?

[#5]

Daylight the earthworks to the top surface, then add a conditional test on both sides.  If the daylight point is above the bottom surface then add another daylight link to finish the section.  Note - you can also reverse the whole thing and daylight to the bottom surface instead.

[#6]

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SBoon wrote:

In this case your material section is going to have a vertical face on the left side, from the toe of earthworks slope down to the base of the soft clay.

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The vertical face I can live with but will the software "create" this itself and thus compute the "correct" volume as the Help seems to suggest?? I would normally do this via Analyse Volumes but the added complexity of several subsurfaces prompted me to try another method (the Analyse volumes would also just "cookie cut" at the edge i.e. assumes a vertical edge).

I'm trying to avoid having to add a new breakline to the earthworks surface based on the levels found at the soft clay horizon.