Use of plastic filter cloth in revetment construction : Potamology Research Project 11
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Littlejohn, Bobby J.
Potamology ReportSummary: This study is part of a program of general investigations for improving the design of stabilization structures on the lower Mississippi River. Many revetment failures occur each year as a result of the subgrade material being eroded through the voids of the articulated concrete revetment mattress. The process of erosion frequently continues until an extensive scour pocket develops beneath the mattress. This can eventually result in a structural failure in the mattress or progressive movement toward the bank and in either case poses the threat of a bank failure. There are some locations where a failure could not be tolerated because of the possible danger to life and property that might result. This stresses the need for providing a greater degree of protection at such locations by modifying the standard revetment design. In recent years, woven cloths have proven very effective in controlling erosion. Limited experiments were first conducted by this District in 1965 in placing woven filter cloth in revetment construction. This study is an extension of those experiments with the objective of determining the feasibility of placing the cloth on the underwater subgrade by attaching the cloth to the mattress squares during casting operations and sinking the unit as a part of the revetment mattress. This report presents a description of the construction procedures and the results of two experimental installations of the cloth. In August 1968, 444 squares were placed at Island 40, Tennessee, with the filter cloth bonded to the bottom sides of the mattress squares using two types of seams previously tested in the laboratory. These did not provide a completely satisfactory bond as the cloth pulled completely loose from seven squares and partially loose from numerous others. As a secondary objective, annual surveys were made to evaluate the performance of this test section against adjacent sections of mattress underlain with the standard gravel blanket, but over the last several years a fill has deposited over the test reach, thus preventing further comparisons. In September 1969, 48 squares were placed at Hickman-Reelfoot, Kentucky, to test two variations of a different type of bonding device consisting of one-quarter inch cords sewn on top of the strips of cloth. In general, the experiments showed that the cloth can be satisfactorily placed on the underwater subgrade by bonding the cloth to the bottom of the mattress squares. The cords sewn on top of the cloth in Experiment No. 2 provided better bonding qualities than the sewn seams used in Experiment No. 1. The cost of mattress in place with the filter cloth attached would be increased by about 25 percent over the cost of standard mattress. However, the use of filter cloth bonded to the mattress squares is recommended for consideration when the requirement for a more effective bank protection at certain locations warrants the additional cost, and particularly in cases where a bank failure would be crucial.
U.S. Army Engineer Waterways Experiment Station.Engineer Research and Development Center (U.S.)
Potamology; Mississippi River; River banks; Bank stabilization; Plastic filter cloth; Revetments; Revetment construction; Hydraulic structures; Embankments
Potamology investigations report ; 21-5.
Approved for public release; distribution is unlimited.