No abstract

Understanding the dynamic behavior of soils is essential to the study of the influence of seismic loads on the instability of submarine slopes, an important issue in Brazil and other countries. The shear modulus and the damping ratio are two fundamental parameters for the study of this behavior. Determining these parameters for Speswhite kaolin clay is the object of the present study using resonant column tests and dynamic centrifuge tests with accelerometers and pairs of bender elements. The curves obtained in the laboratory are compared with empirical curves and comparable data in the literature. Good agreement was observed between experimental data and the empirical prediction for the degradation curve of the normalized shear modulus. The damping curve for very low strains, obtained with resonant column tests, was consistent with the empirical curve. However, consistent with a trend observed in the literature, the centrifuge test results presented considerable scatter (dispersion), attributable to the difficulty in modelling damping dissipation mechanisms in the centrifuge.

Carbonate sand is characterized by the presence of fragile grains, which may influence their mechanical response due to the imposed loading; especially cyclic loading. The shear wave velocity (VS) provides relevant information for the design of foundation inserted in this type of soil, which can be obtained from laboratory tests with the use of bender elements (BE). This paper aims to evaluate the VS value of a carbonate sand from triaxial tests with BE using three methods in the time domain. The influence of loading, unloading and cycling on VS is also evaluated. The results confirmed that the confining stress affects the dynamic parameters. At higher stress levels, the signals aremore susceptible to the near field effects and the dynamic parameters are less influenced by cycling.