Finite element study of patterns of shear zones in granular bodies during plane strain compression   总被引：1，自引：1，他引：0  

Jacek Tejchman  Jarek Górski 《Acta Geotechnica》2010,5(2):95-112

Numerical investigations of patterns of shear zones in granular bodies obtained during quasi-static plane strain compression tests were performed. The effect of a spatially correlated stochastic distribution of the initial void ratio and roughness of horizontal plates was analyzed. To describe a mechanical behavior of a cohesionless granular material during a monotonic deformation path in a plane strain compression test, a micro-polar hypoplastic constitutive model was used. FE calculations were carried out with both initially dense and initially loose cohesionless sand. A Latin hypercube method was applied to generate Gaussian truncated random fields of initial void ratio in a granular specimen. A weak correlation of the initial void ratio in both directions and its large standard deviation were assumed for all specimens. The horizontal boundaries were either ideally smooth or very rough. The FE results show similar patterns of shear zones as compared to experiments.  相似文献   

Experimental metasomatism of monazite and xenotime: mineral stability, REE mobility and fluid composition   总被引：2，自引：0，他引：2  

Callum J. Hetherington  Daniel E. Harlov  Bartosz Budzyń 《Mineralogy and Petrology》2010,99(3-4):165-184

In this study a Th-bearing monazite from a Brazil beach sand, a low Th monazite from a Malawi carbonatite, and a xenotime from a pegmatite in northern Pakistan were experimentally metasomatised in a series of common metamorphic and igneous fluids at 600°C/500 MPa and 900°C/1000 MPa. Fluids included H₂O, NaCl, and KCl brines, CaF₂?+?H₂O, 1m and 2m HCl, 1m and 2m H₂SO₄, 1m NaOH, and Na₂Si₂O₅?+?H₂O. The monazite show a variety of responses to the fluids ranging from no reaction (KCl?+?H₂O) to small compositional changes and partial replacement of the monazite grain rim by Th-enriched monazite in the NaOH and (Na₂Si₂O₅?+?H₂O) experiments respectively. The other acid and brine fluids induced varying degrees of partial dissolution in the monazite and xenotime, but no compositional alteration. Partial replacement of monazite grain rims by Th-enriched monazite occurred only in the alkaline fluids as the result of a coupled dissolution-reprecipitation process.  相似文献   

Modelling hydraulic and capillary-driven two-phase fluid flow in unsaturated concretes at the meso-scale with a unique coupled DEM-CFD technique     

Marek Krzaczek  Michał Nitka  Jacek Tejchman 《国际地质力学数值与分析法杂志》2023,47(1):23-53

The goal of the research was to demonstrate the impact of thin porous interfacial transition zones (ITZs) between aggregates and cement matrix on fluid flow in unsaturated concrete caused by hydraulic/capillary pressure. To demonstrate this impact, a novel coupled approach to simulate the two-phase (water and moist air) flow of hydraulically and capillary-driven fluid in unsaturated concrete was developed. By merging the discrete element method (DEM) with computational fluid dynamics (CFD) under isothermal settings, the process was numerically studied at the meso-scale in two-dimensional conditions. A flow network was used to describe fluid behaviour in a continuous domain between particles. Small concrete specimens of a simplified particle mesostructure were subjected to fully coupled hydro-mechanical simulation tests. A simple uniaxial compression test was used to calibrate the pure DEM represented by bonded spheres, while a permeability and sorptivity test for an assembly of spheres was used to calibrate the pure CFD. For simplified specimens of the pure cement matrix, cement matrix with aggregate, and cement matrix with aggregate and ITZ of a given thickness, DEM/CFD simulations were performed sequentially. The numerical results of permeability and sorptivity were directly compared to the data found in the literature. A satisfactory agreement was achieved. Porous ITZs in concrete were found to reduce sorption by slowing the capillary-driven fluid flow, and to speed the full saturation of pores when sufficiently high hydraulic water pressures were dominant.  相似文献