Network Modelling of the Influence of Swelling on the Transport Behaviour of Bentonite

Abstract

Abstract:Wetting of bentonite is a complex hydro-mechanical process that involves swelling and, if confined, significant structural changes in its void structure. A coupled structural transport network model is proposed to investigate the effect of wetting of bentonite on retention conductivity and swelling pressure response. The transport network of spheres and pipes, representing voids and throats, respectively, relies on Laplace-Young's equation to model the wetting process. The structural network uses a simple elasto-plastic approach without hardening to model the rearrangement of the fabric. Swelling is introduced in the form of an eigenstrain in the structural elements, which are adjacent to water filled spheres. For a constrained cell, swelling is shown to produce plastic strains, which result in a reduction of pipe and sphere spaces and, therefore, influence the conductivity and retention behaviour.

On the influence of cell size on network modelling of water retention and conductivity of geomaterials

“…The retention and conductivity of cells of porous geomaterial are modelled by a network of pipes and spheres with statistical distribution of radii (Athanasiadis et al, 2016;Athanasiadis, 2017). The network is generated by a Voronoi tessellation of randomly placed points which are subject to a minimum distance d min .…”

“…The aim of this study is to investigate the influence of cell size on degree of saturation and conductivity for varying capillary suction representing varying unsaturated conditions. The response will be predicted with a network model based on three-dimensional Voronoi tessellations developed in Athanasiadis et al (2016); Athanasiadis (2017); Athanasiadis et al (2018).…”

Hydro-mechanical network modelling of porous geomaterials

“…However, this is not necessarily the case for conductivity evolution of bentonite under confined conditions (Wang et al, 2013). Athanasiadis et al (2016) presented non-monotonical changes of cell conductivity during wetting based on an extension of the present work where the changes of the pipe and sphere diameters were coupled with mechanical changes of the dual mechanical network. The mechanical elements exhibited swelling (tensile) strains when at least one sphere located around them was wetted to simulate swelling induced wetting.…”

“…Furthermore, the mechanical elements exhibited a simple elastic-plastic behaviour without hardening. Moreover, in Athanasiadis et al (2016), a similar coupling of the mechanical and transport network as those presented in Section 4.3.1 and Section 4.3.1, was used. In this work, pipe radii changes were associated to the plastic strains exhibited by the surrounding elements.…”

“…Then, the overall cell behaviour is evaluated based on a so called computational homogenisation scheme. Hence, the link between the two scales can be analysed at the material point level (Thornton, 2000;Athanasiadis et al, 2016).…”