A portable triaxial cell for beamline imaging of rocks under triaxial state of stress

Amer Syed,David L Jacobson,Yukie Tanino,Eli Baltic,Jacob M Lamanna,Genoveva Burca,Daniel S Hussey

doi:10.1088/1361-6501/abeb94

Abstract

With recent developments in direct imaging techniques using x-ray and neutron imaging, there is an increasing need for efficient test setups to study the mechanical and/or transport behavior of porous rocks. Bespoke designs from commercial suppliers are expensive and often difficult to modify. This paper presents a novel design of a portable triaxial cell for imaging deformation (and a suggested adaptation to introduce fluid transport) through rocks/sand/soil under the triaxial states of stress representative of those encountered in the case of groundwater aquifers or subsurface hydrocarbon reservoirs. The design philosophy and the parameters are detailed so that interested researchers can use this experimental setup as a template to design and modify triaxial cells to suit their own experimental requirements. The design has been used in two imaging beamlines: Imaging and Material Science & Engineering (IMAT), ISIS facility, Harwell, Oxfordshire, UK, and BT2 of the National Institute of Standards and Technology Center for Neutron Research, Gaithersburg, MD, USA. The mass attenuation coefficients extracted from the 2D radiograms of the triaxial cell were compared with those reported in the literature. Further suggestions for the adaptation of the triaxial cells for studying the mechanics of deformation and fracture in rocks are included.

Highlights

Introduction32 (2021) 095403 or cone beam imaging, observations were primarily derived from bulk measurements or 2D imaging techniques such as scanning electron microscopy (SEM) or transmission electron microscopy (TEM) of thin rock sections
This paper presents a novel design of a portable triaxial cell for imaging deformation through rocks/sand/soil under the triaxial states of stress representative of those encountered in the case of groundwater aquifers or subsurface hydrocarbon reservoirs
The mass attenuation coefficients extracted from the 2D radiograms of the triaxial cell were compared with those reported in the literature

Summary

Introduction

32 (2021) 095403 or cone beam imaging, observations were primarily derived from bulk measurements or 2D imaging techniques such as scanning electron microscopy (SEM) or transmission electron microscopy (TEM) of thin rock sections. Using these imaging techniques, one can resolve micrometer to submicrometer features of the grain structure and mechanics, but it is not possible to infer any information about three-dimensional (3D) geometrical features, which are significant for defining the mechanical behavior of geomaterials. Preparation of specimens, for thin sections, may introduce artifacts that could potentially limit the interpretation of experimental observations Another important aspect that is neglected in the case of the SEM/TEM is the reference to the in situ stresses (the natural state of rock in the subsurface). Except for a few hard rocks (e.g. granite), most sedimentary rocks, such as sandstone, are compressible and the granular assembly of the rocks undergoes deformation with the application/release of stress

Methods

Findings

Discussion

Conclusion