Monitoring of the nano-structure response of natural clay under mechanical perturbation using small angle X-ray scattering and digital image correlation

Abstract

This paper introduces a new experimental method to monitor the evolving intra-particle, nanometre-scale response during hydro-mechanical tests on undisturbed wet clay samples using small angle X-ray scattering (SAXS). The method uses a newly developed miniature plane-strain one-dimensional compression cell that facilitates simultaneous full-field surface displacement measurements using digital image correlation and SAXS measurements. The 60-120 s acquisition times offered by SAXS at synchrotron facilities are beneficial to study time-dependent mechanisms in clays. The experimental results presented indicate that, for the natural sensitive clay tested in this work, no significant structural changes occur at the intra-particle scale during loading, even when large strains are measured at the macro-scale. In addition, changes that are observed at this scale occur after the end of perturbation, i.e. the creation of new intra-particle structures. Further information is obtained on the orientation evolution of the fabric by the comparative analysis of the individual mineral component response.

Fabric Investigation of Natural Sensitive Clay from 3D Nano- and Microtomography Data

“…The particle orientations identified are largely horizontal, with a distinct alignment direction in higher resolution data. The mean principal particle orientations with reference to the horizontal plane are calculated for each data set to compare this finding with that of prior studies on particle orientations determined using SAXS in natural clay samples from the same test site and depth (Birmpilis et al 2019). The results, plotted in Fig.…”

“…Methods from materials science, such as scanning and transmission electron microscopy (SEM/TEM), mercury intrusion porosimetry (MIP), and wide or small angle X-ray or neutron scattering (W/SAXS, SANS) (e.g., Glatter and Kratky 1982;Toer and Reimer 1998;Giesche 2006) have been introduced in geomechanics to further probe clays at microscale despite their inherent limitations for use in fine-grained materials (Yao and Liu 2012;Deirieh et al 2018). The ultimate aim is to link the micro and macro response (e.g., Pusch 1970;Delage and Lefebvre 1984;Djéran-Maigre et al 1998;Hicher et al 2000;Ringdal et al 2010;Delage 2010;Hattab and Fleureau 2011;Hattab et al 2013;Suuronen et al 2014;Wensrich et al 2018;Birmpilis et al 2019;Cotecchia et al 2019;Delage and Tessier 2021;Abed and Sołowski 2020;Schuck et al 2020;Dor et al 2020;Zhao et al 2020). Regardless of the experimental method, either a bulk response of the complete sample volume (MIP, W/SAXS, SANS), a twodimensional (2D) map of the integrated response along the transmitted X-ray/electron beam (scanning W/SAXS and TEM), or a 2D surface profile (with a certain depth of view) is obtained (SEM).…”

“…In coarse grained materials, the orientation of contact normal vectors, void vectors, and branch vectors or simply the orientation of the primary axis of the particle (e.g., Bathurst and Rothenburg 1990;Fonseca et al 2013;Kuhn et al 2015) are all used as input for the fabric tensor in contemporary continuum models for coarse grained materials (Wang et al 2020). In contrast, for clay samples, the particle orientations are most often extracted as a measure for fabric from microscopy data (e.g., Cotecchia et al 2019;Zhao et al 2020), W/SAXS (Birmpilis et al 2019), or SANS (Wensrich et al 2018). However, the continuum models starting from the fabric measured experimentally at the particle scale are still in their infancy.…”

“…Values for clay particle orientations from SAXS are included for reference. (Data fromBirmpilis et al 2019. )…”

Insights into the interaction of a shale with CO2

“…Despite the classic testing approaches on centimetric size shale samples in the literature, in this work very small samples (5 mm) are studied in order to first gain in temporal resolution (partly inspired by small-scale permeability testing equipment (Birmpilis et al, 2019;Birmpilis and Dijkstra, 2021), but also to optimise the quality of x-ray imaging (improved spatial resolution). This approach is challenging for the given material and the given subject; the pore size of shales is in the order of nanometres and thus impossible to visualise with x-ray micro-tomography (micrometric scale).…”