Description:

Soil Strength: A Moving Target in Numerical Analysis

With cycles of pore pressure generation and consolidation, soil strength can both reduce and increase significantly during the lifecycle of a geostructure (Fig. 1). Many constitutive models exist that can reproduce this duality of behaviour. However, implementation and calibration of these models in numerical techniques such as the finite element method is difficult due to the need for regularization techniques to alleviate spurious strain localization. Such methods require a ‘length scale’ over which the regularization is performed and appropriate values can be difficult to determine. This seminar will first describe a range of situations in which changing soil strength is critical to the performance of geotechnical infrastructure, illustrated by a simple example based on a classical problem (Fig. 2). A potential method for testing the validity of – and calibrating – strain-softening-hardening models for soil will then be introduced. The proposed method incorporates image-based deformation measurements and aspects of the finite element method so as to remove user bias from the model selection process and to automatically optimise model parameter calibrations.

Biography:
Sam Stanier is currently an ARC DECRA Fellow at the University of Western Australia. He was awarded a PhD in geotechnical engineering in 2011 by the University of Sheffield, UK, and has research interests that span experimental, analytical and numerical modelling of offshore geotechnical problems. Dr Stanier is the lead developer of the image-based deformation measurement software GeoPIV-RG, which is in use by >600 researchers at >250 institutions worldwide. He also has close links with the offshore geotechnical industry and as the lead researcher on the Remote Intelligent Geotechnical Seabed Surveys Joint Industry Project, Dr Stanier has led development of the shallow penetrometers – the ring, toroid and hemiball. These devices mimic subsea pipelines and cables, allowing the evolution of the strength of the seabed to be predicted and incorporated in design. Dr Stanier’s current focus is on developing experimental methods to assess the validity of – and calibrate – strain-softening-hardening constitutive models for soils using image-based deformation measurement techniques.