The shear modulus under very small strains, Gmax, is the physical parameter mainly involved in the characterization of soils subjected to shear in several geotechnical applications. This modulus is also related to the shear wave velocity only via the density of soil. On the other hand, the parameter Vs is gaining more and more popularity. Indeed, it is a parameter mainly required to perform the analysis of the dynamic response of soils, and the codes of building require increasingly to characterize a site with regard to its liquefaction potential. In addition, the developments in last years have made available different methods for measuring Vs in situ and in the laboratory. The in-situ methods appear interesting for economical purposes, in particular those based on the surface waves. On the other hand, the laboratory techniques of Vs measurements can be used to characterize the soils in terms of Vs and to quantify the effects of various parameters on Vs.
The previous factors promote the use of Vs for soil characterization purposes. This doctoral project thus aims to measure Vs in the laboratory using the P-RAT technique (Piezoelectric ring-actuator technique) and, to develop correlations between Vs and the geotechnical properties of the tested soils. The robustness of P-RAT and the performance of their interpretation method for characterizing the coherent soils in the elastic domain (γ <10 -3%) were evaluated based on two series of tests carried out at the UdeS laboratories and ÉTS on similar materials. This promotes the use of P-RAT in other geotechnical devices or laboratories. Series of consolidation tests were performed on specimens from different deposits of eastern Canadian clay and consolidation curves were presented in terms of Vs. Specific empirical correlations were established between the shear wave velocity and more usual geotechnical parameters such as void ratio, effective vertical stress and overconsolidation ratio.
Many correlations have been proposed in the literature to calculate the stiffness under very small strains and therefore Vs. These laboratory correlations have been compiled and grouped into different general forms based on the geotechnical properties used to establish them. The application of these correlations to eastern Canadian clay deposits reveals the scatter between Vs1 values and the effect of K0 coefficient. The dispersion between Vs1MAX and Vs1Min predicted by different forms of correlations and even by correlations which have the same general form was also calculated for each analyzed site. The applicability of existing correlations was assessed by comparing the values of Vs1 obtained based on P-RAT correlations to those predicted by published correlations. P-RAT correlations allow to predict Vs for eastern Canadian clay and appreciate the use of this parameter for geotechnical characterization purposes.
Elbeggo, D. (Author),
Éthier (Supervisor) &
Dubé (Co-supervisor),
27 Apr 2023Student thesis: Doctoral thesis › Doctorate in Engineering: Engineering