To the editor:
RE: Letter to the editor by Bob Barrett (August/September Geosynthetics)
I just read Mr. Barrett’s letter in Geosynthetics—very informative. I have been designing MSE walls since 1992 and have experienced the industry enjoying much success with MSE walls along with someâ€¯failures.
I’ve had discussions with vendors and design/build firms regarding MSE block-wall designs regarding their tendency to reduce the amount of reinforcement in the structure. Their liberal approach to design has contributed to failures and has the potential to make others wary of specifying MSE technology.
In reviewing MSE wall designs developed by engineers, vendors and design/build firms, I have come to the conclusion that some wall designers do not understand the engineeringâ€¯mechanics or design process for reinforced soil design. We are fortunate to have very sophisticated generic design programs, such as those developed by Dr. Dov Leshchinsky (program MSEW) and NCMA (program SrWall)â€¯to assist engineers in performing MSE designs.
Some MSE engineers who use commercially available or free vendor software do not understand the input or output and probably could not justify the design by a hand calculation to support the computer output. A well-known professor of geotechnical engineering, Dr. William Kovacs, P.E., of the University of Rhode Island, made a recent statement regarding geotechnical software today: “garbage in = gospel out.”
I believe that some vendors and design/build contractors involved in MSE wall design and construction (the fox watching the hen house scenario) is also problematic in that they tend to water down the design process so as to reduce the amount of reinforcement to be placed. Using a liberal design approach, and ignoring or incorrectly addressing global stability, accomplishes this.
In short, the design for MSE walls is controlled more through vendors and design/build contractors. Wall designs should be controlled through the engineering community where direct lines of communication can be realized among the civil engineer, geotechnical engineer, and MSE wall engineer.
Blaise J. Fitzpatrick, P.E.
Fitzpatrick Engineering Associates, P.C.
To the editor:
I enjoyed [Bob Barrett’s] letter in Geosynthetics magazine. I am always happy to hear someone in the geotechnical community get frustrated over the lag in technological advance in the United States compared to other parts of the world (or as compared to other engineering disciplines).
I look forward to the advanced utilization and understanding of GRS technologies.
Matthew W. Veenstra, EIT