Effects of particle morphology on the shear response of granular soils by discrete element method and 3D printing technology

Abstract

The development of quantitative correlation between particle morphology and shear responses of granular soils is an ongoing challenge. Herein, 3D printing technology, combined with the experiments and discrete element simulations were conducted to study the effects of different particle shapes on the particle migration, the development of shear zone, and the anisotropy of particle contact during shearing. Both numerical simulations and experimental tests confirmed that the increase of modified shape parameter Sh strengthens the interlock between particles, which in turn limits the shear deformation in the direction of shearing. As the shear load increases further, the rotation of particles begins to develop from both sides of the shear box boundary, which gradually expands to the center, and finally forms a stable disturbance region in the center of the specimen; meanwhile, the positions of the maximum particle rotation appear at the center and boundary of the shear zone. Moreover, particle shape does not affect the distribution of fabric anisotropy before loading, however, the change of particle shape parameter Sh makes the fabric anisotropy become prominent. In addition, particle shape is found to improve the shear resistance by changing the number and distribution of contacts between particles, rather than the contact force among particles.

Macroscopic and Microscopic Characteristics of Strength Degradation of Silty Soil Improved by Regenerated Polyester Fibers under Dry–Wet Cycling

“…It is evident from Figure 7 that with an escalating number of dry-wet cycles, the larger soil aggregates progressively disintegrate into smaller units. Notably, the particle contact modes predominantly transition from face-to-face and edge-to-plane to edge-to-face and point-to-plane configurations [44]. Repeated dry-wet cycles facilitate reciprocal moisture migration within the soil, subjecting soil pores-the conduits for this moisture transfer-to continual washout.…”

“…Small-sized pores are 50-0.1 um. Initially, in the natural state (n = 0), small-and medium-sized pores predominate, constituting 37.5% and 32.2% of the total pore volume, respectively, as compared to the pore volume of compacted clay ascertained using mercury intrusion porosimetry by Ren et al [44]. The main hydration products, such as hydrated calcium silicate and hydrated calcium aluminate, generated by internal hydration and volcanic ash reactions in the improved soil possess particle diameters below 0.001 µm on the nanoscale [45].…”

3D image scanning of gravel soil using in-situ X-ray computed tomography

“…Therefore, regardless of whether intact soil samples are obtained in the field, the observation, quantification, and evaluation of natural sedimentary structures are essential.X-ray computed tomography (CT) is a widely used non-destructive technique for examining objects in medical and industrial applications, as well as in research 10,11 . This technique is useful in geotechnical engineering for observing sedimentary structures or discontinuous planes, such as fissuring, in soil samples 12 ; to quantify physical properties, including particle size and shape characteristics [13][14][15][16] ; to investigate pore and contact fabrics 17,18 ; or to characterize mechanical properties such as shear responses 19,20 primarily using the discrete element method (DEM) [21][22][23][24] or three-dimensional (3D) printing technology to replicate synthetic samples [25][26][27][28][29][30] based on CT images. Such a new paradigm based on imaging, image processing, and computing properties is…”

“…In the aforementioned previous studies, soil or rock samples were obtained in the field or reconstituted in a laboratory before image scanning. The main research focus has been on techniques of processing CT images [17][18][19][20]31,32 , methods of incorporating the results of image processing into their computation [21][22][23][24] , and laboratory tests of synthetic samples [25][26][27][28][29][30] . Moreover, there are no studies on methods of acquiring CT images in-situ, or particularly, methods of scanning the soil samples on-site, that is, in the ground.…”