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|Title:||Rotary cone penetrometer investigations|
|Authors:||United States. Mississippi River Commission.|
U.S. Army Engineer Waterways Experiment Station.
Rotary cone penetrometer
|Publisher:||U.S. Army Engineer Waterways Experiment Station.|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Potamology investigations report ; no. 18-1.|
Summary: This report describes a series of field and laboratory investigations conducted during 1957-1960, as part of a general program concerned with the stabilization of the Mississippi River banks, to develop techniques for use of the rotary cone penetrometer in the field in determining the susceptibility of point bar sand deposits to liquefaction-type failure. Cone penetrometer borings are proposed for this purpose because they are more economical to perform and provide more complete data than undisturbed borings in sand. The first part of the laboratory investigation consisted of cone penetration tests performed on three sands having different gradations, placed in a steel tank at relative densities of 20, 40, 65, and 90%, saturated, and subjected to surcharge pressures of 30, 60, and 100 psi. WES pressure cells were installed in the sand specimens to measure vertical pressure at various depths in the specimens. Results of the tests indicate that cone thrust is a measure of the combined effect of gradation and density. A relation between cone thrust, vertical pressure, and relative density was determined for the different sands tested. Tests were also conducted on laboratory specimens having sand strata of different relative densities to determine the minimum stratum thickness detectable by the cone penetrometer. This thickness was found to be about 6 in. The second part of the laboratory investigation included tests to determine the change in density of sand caused by sampling. Undisturbed tube samples were obtained from sand placed in a steel tank at relative densities generally of 20 and 90%, saturated, and subjected to surcharge pressures of 30, 60, and 80 or 100 psi. The densities of 3-in.-long increments of the samples were measured, and results indicated that the change in density was affected by the vertical pressure and location in the sample tube. In general, the density of dense sands decreased and the density of loose sands increased during sampling. Corrections for the changes in density during sampling were developed and indicated that the change in the central 18-in. portion of a sample 30 in. long is not significant. The field investigation consisted of cone penetration borings made in point bar deposits adjacent to undisturbed and general sample borings. Cone criteria for analysis of cone thrust data and prediction of stability with respect to liquefaction-type failures were developed. Results of the laboratory and field tests indicate that the rotary cone penetrometer measures the combined effects of density and gradation, and can be used to differentiate between stable and unstable sand deposits. It is recommended that the rotary cone penetrometer be used for routine investigation of point bar deposits at proposed revetment sites, and that the cone thrust data be analyzed using the cone criteria proposed in this report. It is also recommended that annual studies of the performance of prediction sites be made for the purpose of verification or improvement of the cone criteria. Appendices A through D describe the cone penetrometer, and the laboratory cone penetration and undisturbed sampling tests in detail. NOTE: This file is large. Allow your browser several minutes to download the file.
|Rights:||Approved for public release; distribution is unlimited.|
|Appears in Collections:||Potamology Investigations Report|
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|Potamology-Investigations-Report-No-18-1.pdf||35.34 MB||Adobe PDF|