Accession Number : AD0693307

Title :   THE SIGNIFICANCE OF CAP AND BASE RESTRAINT IN STRENGTH TESTS ON SOILS,

Corporate Author : CALIFORNIA UNIV BERKELEY OFFICE OF RESEARCH SERVICES

Personal Author(s) : Duncan,J. M. ; Seed,H. Bolton ; Dunlop,P.

Report Date : AUG 1966

Pagination or Media Count : 75

Abstract : The objective of this investigation was to determine the significance of the various effects of cap and base restraint in strength tests on soils. The normal caps and bases used in strength tests prevent lateral expansion of the top and bottom of test specimens. Previous studies have shown that this restraint causes nonuniform volume changes in drained tests, moisture migration in undrained tests, and, in rapidly conducted tests, nonuniformities in pore-water pressure in undrained clay specimens. Lubricated caps and bases were used to eliminate end restraint in undrained triaxial and plane strain tests on undisturbed saturated clay. The results of these tests were compared with the results of tests performed using normal caps and bases to assess the significance of cap and base restraint. These tests showed that the magnitude of the effects of cap and base restraint are not significant. Only in cases where accurate measurement of volume changes are required in drained tests, or where moisture migration must be prevented in undrained tests, will lubricated caps and bases be necessary. In conjunction with this investigation a procedure was developed for insuring the effectiveness of lubrication in eliminating cap and base restraint. The same techniques may also be used to calculate the frictional forces between plane strain specimens and their end plates. (Author)

Descriptors :   (*SOIL MECHANICS, TEST METHODS), DEFORMATION, COMPRESSIVE PROPERTIES, STRAIN(MECHANICS), MOISTURE, POROSITY, CLAY, MUD, SAND, SAN FRANCISCO BAY, LUBRICATION, GREASES, VOLUME, FRICTION

Subject Categories : Soil Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE