CIVIL 3D TUTORIAL: MEASUREMENT OF EARTHWORK FROM THE CORRIDOR AS 3D OBJECTS

1. Introduction

In Autodesk Civil 3D, sometimes, the designer sends us a corridor as a 3D Object.  Extracting certain information on the corridor might prove to be a bit complicated here. Therefore, in this Civil 3D tutorial, we will focus on earthworks and how to extract a surface from the model provided, and finally, through the volume control center, to obtain the m3 of cuttings and embankments. In the model that will be used as an example, the designer has sent us the following:

• The terrain model associated with the location of the corridor.
• The model of the corridor as a 3D object.
• IFC file extracted from the original Civil 3D model.

 

2. Model Configuration

First, we must configure the received model, and as in case of any model we must take into consideration the following aspects: 1- To be able to access the terrain model through the shortcuts of our project. 2- To have the coordinate systems configured, in both models, according to the location of the project and the designer's specifications. 3- To have the surface styles configured, in order to be able to work correctly. (In this step we can import the surface styles from the _AutoCAD_Civil_3D_2018_ENG.dwt template. This can be done in Manage/Styles/Import).  

3. Obtaining the surface of the corridor

Parting from the fact that we only have 3D objects, in order to be able to carry out this operation, we must perform some previous tasks.  

3.1. REMOVING LINES

In order to obtain a surface and given the limitations that Civil 3D imposes on us when handling 3D objects, we must extract the lines from the model and then use them to create the surface. So, for this purpose we must carry out the following steps: 1- We change the workspace to 3D Modeling 2- With the hidden terrain, we select "all" the 3D objects of the corridor and go to the Solid/ Solid Editing/ Extract Edges menu. (This action may require some time depending on the model and the PC you are using). This way we will obtain all the lines that made up our corridor. After this process, they have ceased to be 3D Objects and can be used and manipulated. At this time we are prepared to create our surface.  

3.2. CREATE SURFACE

1- We change back to the initial workspace 2- Create a surface (Toolspace window/ Prospector / Right button on surface / Create Surface). 3- We are now located inside the surface in the section "Drawing objects / Add...” 4- In the pop-up menu, we select lines and accept. Next, we select "all lines" of our corridor and press Enter. 5- We select as surface style: 2D Triangles (Keep in mind that as it is in 2D we must have selected the top view to be able to visualize them). At this time, and generally, creating the surface in Civil 3D creates triangles that should not exist. We must "clean" the surface by eliminating said triangles so that it fits into our corridor. Below we can see the corridor before and after creating the surface:   6- We can perform the elimination of the remaining triangles in two different ways:

• Prospector menu / Surface / {Our surface} / Definition / right button editions / Delete Line.
• Workspace: 3D Modeling

  We select the surface and in the menu that appears Edit/Edit Surface/Delete Line. In this way, we must eliminate all the remaining lines until we match our surface with the model provided (This appears below the surface and we use it as a guide)  

4. Calculating Volume

There are two ways to perform this calculation. Between the two options available, depending on the model we use, we can observe a 2% difference in the total earthwork. Therefore, it is up to the user to decide which is the most optimal in each case.  

4.1. COMPARISON OF EXISTING SURFACES

In this case, the fastest and simplest, we only have to go to menu Analyze / Control center of volumes. We click on 1 and in the pop-up window (2) we use: As Base Surface: The terrain provided Comparison Surface: The created surface We configure the rest of the options and we see the resulting cuttings, filling and calculation of earthworks.  

4.2. COMPARISON OF TWO LAND SURFACES

For this method, it is necessary to create a surface in which the original land will be emptied using our surface created in section 3.  

4.2.1. CREATE SURFACE UNION NATURAL TERRAIN WITH CORRIDOR SURFACE

1- Create new surface (name example: surface_union) 2- In menu Prospector / Surfaces / surface_union / definition / editions Right button / paste surface. We select the natural terrain 3- We create an interior contour in the Definition In the pop-up window, we select hide and name it. 4- In the lower bar it asks us to select object or Surface: Press S to select surface. We select the surface created in the section. 5- We follow the steps of point 2 of this section and select the surface created in section 3.  

4.2.3 COMPARISON OF EXISTING SURFACES

The same steps are followed as in section 4.1.  

5. Example

In this section, we will make a comparison of the measurements provided, from the methods described above and those resulting from the file in IFC format. We take as a sample a given axis: From here we can extract that between the first and second method no significant changes are appreciated in the scope of a large-scale work. However, in the third method, we perceive a remarkable difference that should not exist since it comes from the same model. From this, we can conclude that there is some type of failure in the IFC from Autodesk Civil 3D or a misinterpretation of the volume parameter of slopes and embankments. In addition, it has also been proven that Naviswork is not able to obtain the data related to the measurement based on the IFC provided. Note: At any time reference is made to a specific case, it can not be extrapolated to any IFC format file. This should be one of the correct formats to be able to make measurements. Hence the importance of the IFC being a true reflection of the original model. In any case, it is estimated that the designer/modeler must provide the model prepared to take the measurements correctly and without misunderstandings. In the case of providing an IFC, it must be correctly configured and checked for its agreement with the original model.  

6. Disclaimer

The information contained in this document is based on the personal experience of the author and based on the information provided by Autodesk, therefore it is not possible to ensure that this method works in all cases and/or changes with the update of the program. Sufficient knowledge must be available to address the content of this manual. If you have any questions regarding the procedure, you can find more information and help at https://forums.autodesk.com/.