February 15, 2021
Sponsored by: ZenTek Consultants
The Feature Lines tool, which is standard in Autodesk’s civil infrastructure design software, is all you need to create remarkably detailed grade designs.
Leveling a subdivision lot with yard breaks and side ditches can be difficult. The worries are many: Are your pads the highlight? Do you have a sufficient slope to keep water away from your structures? Have you added high points around the leaching fields?
All of these tasks can seem daunting when working in Civil 3D. We’ve seen people struggle with leveling items, direct surface modifications, and even third-party leveling add-ins in an attempt to deal with batch leveling. One of the most common processes in the civil / construction site design world can, ironically, become one of the most difficult and time consuming.
The good news is, it doesn’t have to be that way. Batch grading can be done in just a few minutes, with great precision and without the need for expensive add-ons or learning new software. In this article, we’re going to walk you through a complete leveling condition using a simple Civil 3D tool – which you probably already know how to use! You just need to apply a little imagination so that it can meet all your batch grading needs.
What tool are we going to use? The simple feature line tool. That’s right, we won’t be using anything other than feature lines to handle a large number of ranking processes. So let’s start with a basic 2D terrain layout, like the one shown below. All of the line art is done with polylines, with no elevations (well, technically “0” is an elevation, but you get what I’m saying).
We’ll start by changing 2D polylines to feature lines, using the FEATURE LINES> CREATE FEATURE LINES FROM OBJECTS tool on the Home ribbon.
We will select all the terrain lines and use the dialog box that appears to erase the underlying polylines and replace them with characteristic lines. We will also use the âAssign Elevationsâ option so that we can tie these lot lines to the existing surface (EG) in the next step.
By clicking “OK” the Assign Elevations dialog box opens, in which you can set all vertices (points) of the feature line to specific elevations or read elevations from a surface. We’re going to read from our existing surface and âInsert mid-level breakpointsâ. This places the elevation data along feature lines at each point where it intersects with the underlying TIN lines of the surface.
Looking in the object viewer, you can see that the property lines are now draped over the surface:
By clicking on each feature line of the terrain and using the ELEVATION EDITOR on the ribbon bar, we can locate and identify the high points on each feature line of the terrain, so that we can set the height of the slab at- above the highest property line point in the next step.
We can repeat the process of creating feature lines from objects and apply a defined elevation (197 in this example) to each of the median, as follows:
Looking again in Object Viewer, we can see that the medians are now the highest points of our lots:
We can use the same process we did for the platforms to generate septic fields, sumps, walkways, etc. Then we can use the WORKING LINE> CREATE WORKING LINE FROM STEP OFFSET command to offset the front yard to get a defined slope / grade up to a yard cutoff.
We will offset the line 25 feet, at a slope of 12% from the front yard line. This gives us the result below:
Note that the elevation of each vertex (blue grip point) is calculated at a slope of 12% from the lower green line in the image above. We can continue this process to create mid-point breaks, etc., as needed. We can also go back to the ELEVATION EDITOR to manually override the specific elevations we need.
Finally, we can use the FEATURE LINE> CREATE FEATURE LINE tool on the Home ribbon to draw things like side yard ditches, culverts, or drainage ditches as appropriate.
When we use the OSNAP tools and snap to a feature line of the land, the elevation of the point we are snapping to is automatically provided to the feature line tool, so we can snap in the middle of the yard, for example, and sketch a drainage channel for backyard runoff using the Slope / Slope / Elevation control options in the Create Terrain Feature Line command.
Looking in the object viewer, you can see that the feature lines of the terrain are tilted towards the design parameters we have defined (a bit exaggerated in this example for visibility) and that we have the contours of a surface. fully developed leveling system.
From there, all we have to do is build a new surface and add all of our designed feature lines to that surface as âbreaklinesâ to achieve a finished grade with detailed contours.
That’s all we can say about it! Terrain feature lines (a standard Civil 3D tool) are all you need to create remarkably detailed grade designs. This approach works for terrains, as shown here, as well as parking lots, steps, roads, curb return conditions, or just about anything you can think of. Take the time to familiarize yourself with the proper use of function lines and what they are capable of; it may be the best time investment you can make in your career as a civil designer.
ZenTek Consultants offers training on AutoCAD Civil 3D and associated processes for the civil / surveying world. If you want to know more about what we offer, visit us at www.zentekconsultants.net.