00229597

Component

http://onlinepubs.trb.org...s/hrr/1968/243/243-006.pdf

CLASSICAL BEARING CAPACITY THEORY IS REVIEWED. A SPECIMEN OF LOESS SILT WAS COMPACTED AT OPTIMUM MOISTURE CONTENT WITH STANDARD COMPACTIVE EFFORT IN CBR MOLDS. THREE SIZES OF SPHERE DIAMETERS WERE USED: 0.75 IN., 0.562 IN., AND 0.50 INCH. ON EACH SPECIMEN THREE TESTS WERE RUN, ONE WITH EACH SPHERE UNDER SIMILAR CONDITIONS. USE OF A SPHERICAL PENETRATION TEST ON A VARIETY OF COHESIVE SOILS GAVE LINEAR PLOTS OF SPHERICAL CONTACT AREA VS. LOAD. THE SLOPE OF THIS PLOT IS TERMED THE SPHERE-BEARING VALUE (SBV). THE SBV WAS FOUND TO BE SAME REGARDLESS OF THE SIZE OF THE SPHERE, SO LONG AS THE SPHERE IS LARGE ENOUGH TO OVERCOME INHOMOGENEITIES IN THE SOIL. MODEL TESTS INDICATED THAT WITH INCREASING LOADS, PENETRATION OF THE SPHERE INITIALLY INVOLVES PSEUDO-ELASTIC COMPRESSION OF COHESIVE SOILS FOLLOWED BY A PLASTIC BEARING CAPACITY FAILURE. THE QUALITATIVE OBSERVATION THAT THE SBV TEST INVOLVES PSEUDO- ELASTIC COMPACTION WAS SUPPORTED BY A CORRELATION BETWEEN SBV AND THE MODULUS OF SUB-GRADE REACTION DETERMINED FROM THE PLATE-BEARING TEST. THE SBV ALSO CORRELATED WITH BEARING CAPACITY VALUES SUCH AS CBR AND PLATE BEARING WITH SEVERAL EXCEPTIONS: THE CORRELATION TO CBR DID NOT HOLD FOR SANDS, OR FOR SILTS EXCEPT NEAR THE OPTIMUM MOISTURE CONTENT. THE SBV CORRELATED CLOSELY WITH BEARING CAPACITY PREDICTED FROM THE TERZAGHI EQUATION USING SOIL SHEAR STRENGTH PARAMETERS. AN SBV FLEXIBLE PAVEMENT DESIGN METHOD BASED ON AN ASSUMED BOUSSINESQ VERTICAL STRESS DISTRIBUTION AND USING A FACTOR OF SAFETY OF 5.5 GAVE PAVEMENT THICKNESSES COMPARABLE TO THOSE OBTAINED BY USING CBR METHODS. ADVANTAGES OF THE SBV FOR BEARING TESTS OF SOILS EXCLUSIVE OF CLEAN SANDS INCLUDE: (1) POSSIBILITY FOR A MORE RAPID ONE-SHOT TEST SINCE THE LOAD-CONTACT AREA RELATIONSHIP IS A STRAIGHT LINE, (2) LOWER COEFFICIENT OF VARIATION AS BETTER REPRODUCTIBILITY OF TEST RESULTS THAN IN CBR AND PLATE BEARING TESTING OF THE SAME SOILS, (3) POSSIBLITY FOR CHANGING THE SPHERE SIZE TO FIT THE SOIL OR THE LOADING EQUIPMENT AVAILABLE WITH NO CHANGE IN SBV, AND (4) ADAPTABILITY FOR REPEATED LOADING AND ELECTRICAL MONITORING.

Paper sponsored by Committee on Soil and Rock Properties. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved

01410187

English

pp 62-74

1968

Highway Research Record

Print

Figures (14) ; References (11) ; Tables (4)

Bearing capacity; Boussinesq equation; California bearing ratio; Coefficient of subgrade reaction; Cohesive soils; Deformation curve; Flexible pavements; Loess; Moisture content; Pavement design; Pavements; Plate bearing test; Silts; Soil compaction; Soil penetration test; Soil tests; Soils; Spheres; Testing; Theory; Thickness

Model tests; Pavement thickness

Geotechnology; Highways; Pavements

TRIS, TRB

Aug 15 2004 2:39AM

• COMPARISON OF FIELD AND LABORATORY MEASUREMENTS OF MODULUS OF DEFORMATION OF A CLAY
• COMPARISON OF LABORATORY AND FIELD VALUES OF CV FOR BOSTON BLUE CLAY
• CONSOLIDATION PROPERTIES OF AN ORGANIC CLAY DETERMINED FROM FIELD OBSERVATIONS
• FIELD AND LABORATORY STUDIES OF MODULUS OF ELASTICITY OF A CLAY TILL
• IN SITU PERMEABILITIES FOR DETERMINING RATES OF CONSOLIDATION
• SUMMARY AND EVALUATION OF SYMPOSIUM PAPERS