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The dynamic properties of clay deposits under seismic or wave loading conditions must be well understood to assure dynamic stability of structures founded on such soil. The dynamic shear modulus and damping appear to be a complex function of many variables, and a wide range of values have been reported in the literature. Consequently, considerable uncertainty exists in choosing the appropriate values of shear modulus and damping for a particular problem. This thesis presents a study of the influence of various factors on the shear modulus and damping of a marine clay using a resonant column/torsional shear device. In particular, the influence of factors such as shear strain amplitude, effective confining stress, stress history, frequency (strain rate), and secondary time-dependent behaviour are examined. The pore pressure response is also studied. The shear modulus was found to degrade for shear strains above 0.005%. The strain dependency was found to be well represented by a single normalized modulus reduction curve regardless of the confining pressure or overconsolidation ratio. Slower strain rates resulted in smaller values of shear modulus. Of the variables studied, the duration of sample confinement was found to be the most imporant factor affecting the material damping. Above 0.005% strain, the damping of the marine clay increased with shearing strain amplitude. No significant effect of confining pressure and stress history on damping was observed at any strain level. As well, the material damping was found to be relatively independent of loading frequency. Both the shear wave velocity and damping obtained in this study were found to be consistent with the in situ values determined using the seismic cone penetration test. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The major objective of this research was to advance the state of the art in interpretation and application of results from in-situ testing of soil, in particular the Cone Penetration Test (CPT), the Self-boring Pressuremeter Test (SBPMT) and the Flat Plate Dilatometer Test (DMT). This study critically examines the equipment, field procedures and methods of test interpretation so that improvements can be made in their application to field liquefaction assessment. Improvements to in-situ test equipment and procedures are proposed. Improvements for the interpretation of CPT data in sands for evaluating relative density, friction angle and modulus are made. A method for prediction of deformation characteristics of clay from CPT data is proposed by incorporating the influence of soil stiffness. A correlation between cyclic stress ratio to cause liquefaction (10 percent double amplitude shear strain) and cone penetration resistance is proposed for sands and silty sands. The proposed CPT liquefaction correlation is substantiated using data from B.C., Japan, China and U.S.A. and appears to represent a good lower bound. The addition of continuous pore pressure measurements during cone penetration is shown to significantly improve the interpretation of the CPT. Data is also presented that clarifies the correlation between the Standard Penetration Test (SPT) and the CPT. Improvements are suggested for the interpretation of SBPMT data in sands for friction angle and modulus. These improvements are applied to the assessment of liquefaction resistance using the SBPMT. New correlations are proposed for estimating the relative density and liquefaction resistance of sand using the results from DMT. A field and laboratory study is carried out to evaluate existing and proposed methods of interpretation of in-situ tests and their application to the assessment of liquefaction resistance. In general the proposed new correlations produce good results, although further field verification is required. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

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

2 volumes in 2 separate files.