3D evolution of sand fracture under 1D compression

Abstract

Three-dimensional (3D) synchrotron microtomography (SMT) and the discrete-element method (DEM) were used to investigate the evolution of particle fracture and deformation behaviour of a granular assembly subjected to the k 0 -loading condition. A series of one-dimensional (1D) compression laboratory experiments were first conducted to better understand the effect of specimen aspect ratio (height-to-diameter ratio, H/D) on deformation behaviour, which demonstrated that changing the specimen aspect ratio influences the stress-strain response of sand. 1D compression was simulated using a 3D DEM model by mapping particle positions from SMT images. Crushable sand particles were modelled in DEM using agglomerates of spherical sub-particles that were bonded by parallel bonds. The DEM model successfully predicted the compressive behaviour of specimens with different aspect ratios. The experimental and DEM results show that the onset of particle fracture and specimen yielding occur at the same strain level. The evolution and distribution of particle fracture were analysed non-destructively at the particle and specimen scales using SMT images and the DEM model. The SMT images revealed that the majority of the particle fracture occurred in particles close to the loading platen. The onset of the fracture pattern of individual sand particles within the granular assembly was also examined at consecutive strain levels using SMT images and DEM simulation results. The development and collapse of force chains were investigated using the DEM model and it was observed that the agglomerates that are part of a strong force chain mostly experience bond breakages. Combining SMT imaging technique and DEM simulations provided valuable insight into complex micromechanical processes occurring during the compression of crushable granular materials.

An investigation of single sand particle fracture using X-ray micro-tomography

“…Grain-scale observations enrich our understanding with the full kinematics (i.e. three-dimensional (3D) displacements and rotations) of all the individual sand grains in a specimen (Hall et al, 2010), the evolution of 3D particle morphology and fabric of a real sand under loading (Fonseca et al, 2012(Fonseca et al, , 2013, and the evolution and distribution of particle breakage (Andò et al, 2013;Cil & Alshibli, 2014). The fracture of silica sand particles has been examined experimentally with 3D synchrotron tomography and numerically with 3D DEM simulations simultaneously (Cil & Alshibli, 2012, 2014.…”

Correlation Relationship Analysis of Physical Mechanics Properties and Pores Microstructures

“…Samples of SFG soil (0kPa, 100kPa, 200kPa, 400kPa, 800kPa and 1600kPa) have similar materials and physical properties [5].Group densities were obtainedby XRD and XRF tests [6].…”

Evolution of deformation and breakage in sand studied using X-ray tomography

“…Such detailed study is nearly impossible to perform on a full specimen, because there are significant limitations in image resolution as well as the computational time needed to perform measurements on each particle. Cil & Alshibli (2014) studied the evolution of sand fracture under one-dimensional (oedometric) compression. They studied the effect of the slenderness ratio of a loose sand assembly with uniform grading, used images from synchrotron to visualise the grains (number, position and deformation), and then made a qualitative comparison of the deformation process with a discrete-element method (DEM) model.…”