Modeling Finished and Subgrade Surfaces for a FL DOT Typical Section

Some users from Florida asked me to show them how I would model up the Finished Grade and Subgrade surfaces for a Typical Section from FL DOT for a project they were working on. The enclosed video show the process of modeling the Finished Grade, Asphalt, Sub Base and Base Course surfaces as well as the subgrade models below and behind the back of curb areas.

Key takeaways on the processes used

Get the Finished Grade Model working 100% before starting to model the subgrades - you can still come back and make minor modifications later but the more complete the FG is before you start modeling the subgrade the better. That means adding slope tables to pavement elements to transition cross slopes and adding 2D lines or offset tables to transition widths of the pavement elements in order to compute the FG surface. Also start and stop elements like shoulders or C&G sections across intersections so that you are modeling the entire mainline.

Build your Materials List in the MSI Manager. Most of the materials used in the Road Bed should be defined in the Earthen (Select) category. Give each material a clearly different color so that you can clearly differentiate between the materials in the Template Editor.

Once you have the Finished Grade in place, build each subgrade surface in sequence - like base of Asphalt, base of C&G, Base of Aggregate, Base of Subgrade etc. Use Comment Instructions to separate the key areas (Left / Right), (Finished, Subgrade 1, Subgrade 2 etc.), (Pavement Area, Side / Edge details etc. as you find logical for yourself). Be logical - create all the Offset Elevation Instructions first, then build your Connectors or Offset Slopes second etc.). Note the subgrades will tie up vertically to whatever is above them, so if you need to stop a material layer from tying all the way up to FG you need to have a material layer above it that will stop it from tying all the way up. You do not have to create the vertical walls at the ends of all the subgrades - sometimes they help, sometimes they don’t. You also do not have to apply small offsets everywhere to separate materials, the software will do minor nudges of nodes to make them non vertical if needed. The only time you need to do this is if something is not working quite right for you.

Do not densify the surface too much while you are building the model - set your computation interval to e.g. 25’ and turn off densification and alignment based surface computations. While building the template, having the surface model update with every change to the template will slow you down, set the Rebuild method for the surface to Rebuild by User or Show Empty until you are ready to review the results - if you set it to By User - rebuild when you have finished a set of steps rather than after each step. Do not build additional corridor surfaces or cut fill maps early on in the process unless you immediately set them to By User or Show Empty or Delete them while you continue to build your model - remember the Corridor Model as displayed in the Template editor will update very quickly whereas the corridor surface models need to generate / re-compute all of the surface data and then triangulate before you can make the next template change - on big jobs this will slow you down significantly.

Remember also that you can build a corridor surface model output for any material layer interface in the model, you can have multiple corridor surfaces for a single corridor - one for each material layer as needed. These can help you check the results of your work in 3D view once you are happy you have your model as you want it.

Try to minimize the number of instructions that you create - if you have 24’ or 36’ of pavement in 2 or 3 lanes all at the same cross section, you do not necessarily need a node at every lane edge, unless the pavement thickness varies, or if you have a Mill out process on lanes 2 and 3 or if you have variable depth pavement on each lane for some reason. Keep the template minimal.

If the template is something that you will use on other projects, create a Master project for FL DOT projects, and keep a copy of the Templates that you created in that master project, then you can just Copy and Paste them from the master into your working project when you need them - this can save hours of work over the course of a year - this is the subject of another video I guess

Here is the video

Typical Cross Section PDF
TYPICAL.pdf (253.0 KB)

Curb and Gutter Section Specifications
Florida DOT Curb and Gutter.pdf (345.3 KB)

Completed VCE Project File
Example Project.vce (386.4 KB)