C3D Create corridor

Is there a way to create a corridor WITHOUT an assembly and using surfaces instead? I need to create a subgrade layer by importing points down an alignment. I know how to import points... create surfaces from points...etc. I dont know if this is possible. I'm curently doing this in Terramodel but would like to switch programs.

Thanks

well, you can try to draw yourself a surface,

works first in 2D, draw the corridor lines [splines or curves] and the slope lines [offset], then change the position of the lines in 3D [elevations]

then draw point in the lines [as you consider],, select them & import into C3D and create a surface with them [& mach it with your current surface]

or directly proyect the lines in your surface [if you got it]

have a look this aswell, may be will usefull for you...

_http://www.cadtutor.net/forum/showthread.php?77353-Having-trouble-scaling-an-xref-image-in-autocad

... also check gradding tools, sometimes are quick easy