Linking shape and rotation of grains during triaxial compression of sand
- PDF / 9,586,921 Bytes
- 21 Pages / 595.276 x 790.866 pts Page_size
- 73 Downloads / 193 Views
ORIGINAL PAPER
Linking shape and rotation of grains during triaxial compression of sand Riccardo Rorato1 · Marcos Arroyo Alvarez de Toledo1 · Edward Carlo Giorgio Andò2 · Antonio Gens1 · Gioacchino Viggiani2 Received: 18 February 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Particle shape has a strong effect on the mechanical response of coarse soils. This has been usually observed examining specimen-scale or engineering-scale responses, which are the sum of many microscale interactions. In this work we observe the effects of particle shape directly at the microscale level. X-ray tomography (μ-CT) of two sand specimens is exploited to measure three-dimensional particle shape descriptors but also to track individual particle motions during triaxial compression. A discrete digital volume correlation algorithm is employed to track the motion of individual grains (around 50,000 for each sand specimen) during the test and measure, with good precision, their cumulated displacements and rotations. The specimens examined failed in a clearly localised shear mode. Advantage is taken of this to obtain data relevant for very different kinematical regimes: one uniform and more constrained and the other close to critical state. A direct comparison between the shape and kinematic databases shows to what degree particle shape descriptors are related to observed kinematics. It appears that true sphericity is a good predictor of upper bound rotational restraint. Keywords Laboratory equipment · Microscopy · Particle-scale behaviour · Sands · Shear strength · Statistical analysis
1 Introduction Granular soils are made of discrete particles that interact with each other, therefore changes at the small-scale (i.e., grain-scale) affect the material response at the large-scale (i.e., engineering-scale) [1–3]. For granular soils, for * Riccardo Rorato [email protected] Marcos Arroyo Alvarez de Toledo [email protected] Edward Carlo Giorgio Andò edward.ando@3sr‑grenoble.fr Antonio Gens [email protected] Gioacchino Viggiani cino.viggiani@3sr‑grenoble.fr 1
Department of Civil and Environmental Engineering, Universitat Politécnica de Catalunya (UPC), UPC – Barcelonatech, Moduli D2 Campus Nord UPC – Office 212, C Jordi Girona 1‑3, 08034 Barcelona, Spain
Univ. Grenoble Alpes, CNRS, Grenoble INP, 3SR, 38000 Grenoble, France
2
instance, it is well-documented that particle shape strongly affects soil properties such as extreme void ratios [4, 5], critical state friction [6] or dilatancy and peak friction [7], as well as engineering scale responses, like liquefaction resistance [8] or cone tip resistance [9]. It follows that particle shape must affect grain-scale interactions to produce those effects. This hypothesis has been repeatedly supported, from various perspectives, by the results of numerical simulation. In numerous discrete element models (DEM) direct control of element shape has been shown to result in major changes in ensemble mechanical responses [10–15]. Similar ensemble
Data Loading...
