The effect of particle gradation on the undrained monotonic and cyclic loading behaviour is presented. Straight line gradations of Earls Creek sand with varying coefficients of uniformity and identical mineralogy and D₅₀ were tested, using the triaxial test. Improved sample preparation techniques were used to ensure sample uniformity. The data indicates that, under monotonic loading, the relative shear-induced compressibilities due to a variation in the coefficient of uniformity are a function of the type of loading. Cyclic loading tests on isotropically consolidated samples showed that the effect of particle gradation depends on the relative density. At low relative densities, (less than about 45%), the well graded sand had greater cyclic strength than the uniform sand. At high relative densities, (greater than about 60%), this trend was reversed. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

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The Full-Displacement Pressuremeter (FDPM) Test is one in which a pressuremeter is installed in the soil by pushing it behind a conical tip. Earlier work had indicated that the unload-reload modulus measured with the FDPM was very similar to that obtained from self-boring pressuremeter (SBPM) testing. It had also been suggested that if the pressuremeter was capable of sufficient expansion, the interpreted soil properties would be those of the soil beyond the zone of disturbance. This study examined the factors affecting the measurement, analysis and interpretation of soil properties from FDPM pressure-expansion curves in sands with emphasis on the unload-reload modulus. The effects of equipment design and dimensions, installation method and of test procedure on the analysis and interpretation of lateral stress, shear strength and stiffness were studied during laboratory and field evaluation of two prototype FDPMs. The overwhelming importance of instrument dimensions and tolerances on the test results was clearly shown. Movements of a fraction of a millimetre can have a large effect on the measured lateral stress and stiffness. Test procedures were also shown to have a large effect on the data obtained. It was demonstrated that rate effects became important in pressuremeter tests involving expansion to large strains and a stress-strain strain rate concept was proposed to aid in the understanding of these effects. Theories developed for the interpretation of shear strength of sands from SBPM tests were shown to be inapplicable to the interpretation of FDPM test results. The unload-reload modulus was shown to be an indicator of soil stiffness but the effects of stress level and degree of unloading have to be considered when attempting to derive a stiffness for design. A rational approach to the interpretation of modulus was presented and it was shown that unload-reload moduli from both SBPM and FDPM could be interpreted using the same approach. The need for standardising the equipment design, testing procedures and methods of analysis and interpretation was shown. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

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The development of Marchetti's flat dilatometer, method of testing, changes of Marchetti's (1980,1981) original correlations and Schmertmann's (1982,1983) proposed correlations are briefly described. Factors affecting results of the dilatometer test (DMT) are discussed. In order to improve the understanding of the Marchetti dilatometer test (DMT), an electronic research dilatometer was developed at UBC. The research dilatometer can measure; pore pressure at the center of the membrane, membrane displacement, applied pressure, pushing force and verticality. Test results obtained from the research dilatometer in sand and in clayey deposits at 4 sites in the Lower Mainland of B.C. are presented. Soil parameters interpretated using Marchetti's (1980,1981) and Schmertmann's (1982,1983) correlations are discussed. Comparison is made to other in-situ testing methods such as cone penetration test, vane shear test and pressuremeter test. Based on a better understanding of the DMT, future potential methods of improving or checking the existing correlations are proposed. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate