GE ENG 5471: Rock Engineering

Assignment 1: Learning FLAC

In the first two assignments we will be learning some simple modeling using FLAC. FLAC is one of the premier modeling programs in our field. In this first assignment I will just ask you to follow an easy tutorial. This version of FLAC, has a command line interface. (Sorry about that, but it is not too difficult to use). It will acquaint you with the basics of this type of modeling. Read the entire assignment before beginning work.

We will start real simple with a demonstration problem.

1. Please read the PowerPoint presentation “Modelling Discontinuous Rock with FLAC and UDEC” posted on the GE 5471 Course Website.

2. FLAC software is available in B12 McNutt. [Distance students please download the demo FLAC program from the Itasca website, http://www.itascacg.com/software/demos.php. You can also simply search for Itasca Flac. You will need to create a login at Itasca to obtain the download.]

3. Please download and work through the “demoflac” exercise on the GE 5471 Course Website. The “demoflac” exercise demonstrates many of the features available within FLAC. Not all these features are necessary to complete the assignment.

4. When you have completed the “demoflac” to your satisfaction, please change some material property or another, to make the supported trench in Figure 5 of the “demoflac” file less stable. (Remove the beams or change beam properties or change rock properties or change the trench geometry, or a combination of any, and step until the trench fails).

5. Note: The easiest way to work in FLAC is to create a xxx.txt file and put the series of FLAC commands into that file, and use the command call xxx.txt to run the program. You do not have access to the file tut.dat as suggested in the “demoflac” document. It you run into difficultly please send the TA your xxx.txt file with your list of commands and he’ll can see if there is anything wrong with it.

6. Alternately you can work through “Tutorial (Revised)” file. This file is the abridged version of “demoflac” and explains only the steps needed to complete this assignment.

7. Please give me 2 copies of your Figure 5 (screen shot), 1 before and 1 after failure and describe what you changed to create the failure and why this change caused the trench to fail.

Notes: Please read the theory behind FLAC in the “Modelling Discontinuous Rock with FLAC and UDEC” ppt. This material will not be on an exam or anything but it will help some of you to understand what is going on. To run a FLAC program, a series of steps need to be undertaken, which are explained for you in the “demoflac” and “Tutorial (Revised)” examples:

1. You set up a grid.

2. You assign a constitutive model.

3. You assign material properties to each element. 4. You input put boundary conditions. (If you don’t fix the problem in space, once you apply gravity, your entire grid will start accelerating downward.

5. You set the acceleration due to gravity.

6. You solve the problem by timestepping. (eg. SOLVE or STEP 1000, etc.)

7. At any time you can print or plot coordinates, stresses, displacements, velocities, etc. (Note include the word hold in the command if using the xxx.txt file, e.g. “Plot grid yellow hold”).

8. At any time you can modify anything in the problem and continue timestepping. This includes installing structural elements as shown in the “demoflac”.

Deliverables: 1-2 page memo (use the provided memo format!) outlining the assignment. Include 2 figures, 1 of the original configuration, and 1 of the modified/failed configuration. Make sure the figures are labeled appropriately.

Include at least 1 paragraph explaining what FLAC software is and then continue on with your outline of the assignment. Think of how you would explain FLAC to your non-geological engineering roommate.

Grading: Memo format – 2 points, Memo Content – 6 points, Screen Shots – 2 points.

Due date: August 39, 2017 (08/39/2017) @ 4 p.m. to the TA’s email ([email protected]).

Include the course name (GE5471), student name, and assignment name in the email subject line.