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Title: Consolidated-undrained triaxial creep tests of St. Charles Parish Lakefront foundation clays
Authors: United States. Army. Corps of Engineers. Lower Mississippi Valley Division.
Johnson, Lawrence D.
Keywords: Ciays
St. Charles Parish lake front clays
St. Charles
Consolidated undrained triaxial creep tests
Soil mechanics
Soil creep
Soil tests
Soil testing
Clay soils
Atchafalaya River floodway
Publisher: Soils and Pavements Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Description: Miscellaneous Paper
Abstract: The design, construction, and maintenance of levees on the soft plastic clay soils of the Atchafalaya River floodway have posed a problem for many years because of large settleI11.ents on the order of 10 to 20 ft. Some settlement is attributed to consolidation by dissipation of excess pore water pressure, but a substantial amount results from creep, a continuous no volume change, time-dependent deformation under a sustained shearing stress. Preliminary long-term creep tests were performed on specimens of the St. Charles Parish Lakefront soils to evaluate testing equipment and to determine general trends in long-term creep behavior. The tests were performed in standard triaxial cells with some modifications. Results of the tests indicated that the temperature control system to reduce temperature-induced variations in pore water pressures was satisfactory. The frictionless seals adopted to minimize friction between the loading rod and the piston housing of the chamber were also satisfactory. Silicone oil was used as a confining fluid to prevent changes in specimen water content. Significant reductions in water content did occur during the long-term undrained creep tests; these were attributed to absorption and diffusion of the pore water through the silicone oil and rubber membranes inclosing the specimens. The nullmatic regulators periodically clogged during the longterm tests and temporarily reduced the chamber confining pressure causing some distortion of the creep data. The creep behavior of the test specimens can generally be approximated by the phenomenological model developed by Singh and Mitchell. Creep rupture was observed for stress levels at 80 percent of the peak failure strength, which was above the yield stress. The creep tests were discontinued after about 0.5 x 10^6 minutes (one year) of continuous deformation due to the abovementioned technical problems. The peak failure strength of the long-term creep specimens was greater than the peak failure strength of conventionally tested specimens, presumably due to drying of the creep specimens.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Miscellaneous Paper

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