Assessment of the microstructure effects on the site dynamic response of residual soils

It has been widely recognized that parameters usually used to characterize de dynamic behavior of geomaterials (G/G(max), D/D-min, gamma, V-s), in small strain domain (gamma<10(-3)), are controlled primarily by the confinement level, the type of material and the microstructure (arrangement of particles + interparticle forces). In residual soils, the development of chemical weathering controls microstructural features and plays a fundamental role in the dynamic response of weathering profiles. The effect of microstructure in seismic ground movements of residual soils was studied by using a linear equivalent site dynamic response for two strong earthquakes. Two soil profiles were analyzed in which the dynamic properties of the soil profiles were established via resonant column testing for natural microstructured and destructured states, incorporating the effects of capillary (matric suction) forces. It was found that the effects of matric suction and net confinement is low in ground motion parameters, compared with those of cementation and particle bonding. Dynamic analysis is emerging as a novel tool for the study of the effects of microstructure in geotechnical problems.