PLENARY LECTURE - Simulation-aided geotechnical site investigation

Abstract

With the advancement of computational geomechanics over the past decades, most of the activities typical of site characterization, such as in situ testing or sampling, can be realistically simulated using appropriate constitutive models and balance equations for geomaterials. These numerical simulations are not only informative of the processes that take place during testing but can be used to assess the reliability of current practice empirical interpretation techniques or even propose new interpretation techniques. In this paper, we present two numerical analyses of long-standing geotechnical problems in which new insights are gained by means of advanced numerical modelling. The first analysis corresponds to cone penetration testing in undrained, brittle geomaterials; we describe the effect of the constitutive parameters on cone metrics, and we propose a novel procedure to estimate the initial state parameter from CPTu based on a wide-ranging parametric analysis. The second analysis involves tube sampling in undrained geomaterials. A total stress analysis allows us to describe the kinematics of the soil during tube insertion and evaluate the effect of the tube geometry on the strain path of the problem. The analysis is then extended by considering a fully coupled hydromechanical formulation and a critical state constitutive model for cemented soils; by simulating conventional laboratory tests on the soil that has entered the tube we can quantify sampling disturbance in terms of geotechnical design parameters (e.g. undrained shear strength and yield stress). The possibilities offered by numerical modelling for site characterization are far from being fully exploited. It is envisaged that in the future site-specific numerical analyses will become available, enabling a more comprehensive understanding of the subsurface conditions.

Full Paper