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|Title:||Effects of back-pressure saturation techniques on results of R triaxial compression tests|
|Authors:||Donaghe, Robert T.|
Townsend, Frank C.
Back pressure saturation
Triaxial shear tests
|Publisher:||Geotechnical Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Miscellaneous paper (U.S. Army Engineer Waterways Experiment Station) ; GL-79-12.|
Abstract: Corps of Engineers (CE) soil laboratories achieve 100 percent saturation of R and R triaxial compression test specimens by the use of back pressure applied in small increments concurrently with increase in chamber pressure with adequate time between increments to permit equalization of pore-water pressure throughout the specimen. The objective of this procedure is to apply sufficient pressure on the pore water and pore air so that the air is dissolved in the pore water without significantly prestressing (overconsolidating) the specimen. The objectives of this investigation were to determine the effects of the magnitude of back pressure and the procedure by which it is applied on the stress deformation characteristics of soils. The objectives were achieved by comparing results of tests performed on compacted specimens of Vicksburg loess (clayey silt (ML)) and Vicksburg buckshot (plastic clay (CH)) in which the backpressure saturation procedure was varied and results of tests performed on specimens of Vicksburg buckshot consolidated from a slurry in which the magnitude of the total back pressure was varied. The results indicate that variations in the technique of applying back pressure may significantly affect test results. However, there are no significant effects on test results if procedures outlined in the CE soils testing manual are followed; i.e ., results are not significantly affected if the effective consolidation stress during saturation does not exceed 5 psi and the magnitude of back-pressure increments is controlled so that the effective stress on the specimen is less than the desired consolidation pressure . Appendix A presents the back-pressure saturation procedure specified in Engineer Manual 1110-2-1906. Appendices B and C of the report contain descriptions of an automatic back-pressure saturation device that duplicates the saturation procedure outlined in the CE soils testing manual and of a differential vacuum saturation procedure that enables specimens to be saturated using back pressures equal to field hydrostatic conditions, respectively.
|Rights:||Approved for public release; distribution is unlimited.|
|Appears in Collections:||Miscellaneous Paper|
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|MP-GL-79-12.pdf||8.58 MB||Adobe PDF|