AutoCAD Civil 3D

[#1]

Hi

Am I missing something with the borehole importer.  What use is it, if it just triangulates between boreholes?  Surely there should be an option to be able to set an average offset of the existing ground where there are no BH information?  Or is there?  I cannot seem to find information that sorts this.  Can anyone help?

Regards

Martin

[#2]

Sounds to me like you could lower EG and add the borehole data to it?

[#3]

Hi Joe

Thanks for your reply

Although, I dont follow....  how does this solve the problem?  I could still end up with below ground triangles going through EG.  If I have a valley, and 1 borehole either side, the BH info will interpolate those 2, and will not take into account the EG triangles and go straight through it.  Have you used the borehole importer?

Thanks

Martin

[#4]

The method to overcome this is:

Create a surface for the stratum of interest where the z value is the depth (+ve) in your local units e.g. m

Create a volume surface using the stratum as base surface and EG as comparison

Paste this to a new surface and you have a dynamic stratum surface for volume calcs, profiles etc

If more borehole info becomes available simply add to the stratum depth surface and rebuild.

This will accurately reflect valleys and ditches and hills (which may not be geologically correct) but is usually ok

[#5]

Hi Neily

Are you saying, the strata is basically an offset from EG?  I need to be able to use the surface created from the BH Importer.

[#6]

The input to the borehole importer requires units to be cm and -ve to allow the borehole sticks to be drawn correctly in profiles views. You'll need to manipulate the borehole importer points to be in m and +ve.

DO NOT USE THE REDUCED LEVEL SURFACE THAT THE IMPORTER DERIVES AS IT IS INADEQUATE AS YOU HAVE FOUND

If you follow the steps posted and disply tooltips you will find for example that if at a certian location EG=100m and BHdepth = 6m, BH volsurf = 96m, Stratum surface = 96m. The stratum surface will mirror the ground effectively offset by the bh depth surface so you dont get the " I could still end up with below ground triangles going through EG.  If I have a valley, and 1 borehole either side, the BH info will interpolate those 2, and will not take into account the EG triangles and go straight through it" problem

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[#7]

Great, thanks Neily, will give that a try.  You have to forgive and bear with me, my wee brain struggles, lol.

Martin

[#8]

Yes - its a bit confusing for me at times and I've been using this technique for a long time...!!! It is pretty obvious when you think a little about it though.

The main assumption is that the subsurface strata varies based on how C3D triangulates between the borehole/trial pit locations which may not be the correct assumption and depends on the density of the boreholes/trialpits.

A similar technique (that'll really make your brain hurt) for removing the construction thickness for volume calcs can be found here http://ericchappell.blogspot.com/2012/01/magical-way-to-calculate-volumes.html