Geotechnical Engineering Case

On October 19th, Bill Wuellner from CGC came to class to discuss Geotechnical Engineering. Bill has 40 years are experience and has been with CGC for 20 years. To get projects, CGC will bid competitively, have private landowners come to them, and have competitive or negotiated requests for proposals. The typical steps in a geotechnical engineering project begins with acquiring the work. After this, a proposal is submitted, and the tasks are coordinated. During the drilling phase the bore holes will be staked, a field log will be prepared, and tests will be performed in the field such as the standard penetrometer test. After boring, the material sample will be analyzed to determine the bearing pressure, estimate settlement, and determine if …show more content…
The owner of the house wanted to raise the elevation of the house above the high water mark for a 100-year flood. It was determined that the house would need to be raised 2 feet above the flood stage, build a new foundation, then lower the house onto the new foundation. A few issues associated with the project was the high moisture content and organic materials percentage of the underlying material. In addition, soft materials were found to a depth of 30 feet. Bill explained that typically this type of material would require a deep foundation, such as pile, but in this case he was working with a relatively light 2 story wood framed structure. The first option was helical piers, which are essentially large screws that are drilled into the ground, that can act as a foundation. This option as vetoed by the owner because it was too expensive. Eventually CGC and the owner came to a compromise, to perform a partial undercut and replacement. The contractor removed peat and marl and left the soft clays. To reduce the amount of settlement, the house would be floated in, the stresses on the soils would not be increased. To do this, geofoam was used to reduce the weight of the home, and stone was sued to distribute the load. When dealing with the geofoam, buoyancy had to be considered, since during floods the foam would be underwater, and thus would exert a buoyancy force on the home. On the …show more content…
He explained the engineer only sees a small portion of the soil and that based on the small portion, engineering decisions must be made. He said to be comfortable with uncertainty and to design conservatively to mitigate any issues. In addition, the project should be monitored to ensure that any unforeseen issues do not develop. I found Bill’s presentation to be very informative. He gave me a new interest in geotechnical engineering that I did not have prior to his presentation. The ability to work both in and out of the office, while staying in a central location interests me. To learn how to make good engineering judgements I need more experience. The best way to learn would be to work under a senior engineer who can pass down