A 3D visualization method for identifying fabric characteristics during suffusion using transparent soil

For internally unstable soil, fine particles might migrate in the pore channels of its coarse matrix because of seepage flow, and fluctuations in the hydraulic gradient might promote this migration. To reveal the mechanism for this behavior, simulation testing using transparent soil was employed to visualize the soil mesostructure and particle migration process. Three gap-graded transparent soils with internal stability ranging from unstable to marginally stable and stable were made by mixing different amounts of fine particles. First, comparative seepage tests were conducted on the three soils under steady and fluctuating hydraulic conditions. The effect of hydraulic fluctuations depends on the internal stability of the soil. For the internally unstable or marginally stable soils, hydraulic fluctuations promoted internal instability, whereas for the internally stable soil, small applied hydraulic fluctuations had negligible effects on the measured hydraulic characteristics. Particle bridging during the migration process was used to explain the different behaviors. To verify this concept, a two-stage seepage test was performed, and a three-dimensional digital mesostructural model of the specimen was reconstructed based on continuously scanned images of cross sections. The comparison of the digital models at different stages provided visual evidence of particle bridging. It clearly showed that fine particles bridged at some pore constrictions, and the bridges remained intact during the first steady seepage stage and blocked particle migration paths. During the subsequent fluctuating seepage stage, these particle bridges disappeared, and particle migration resumed.

A semi-resolved CFD-DEM model for seepage-induced fine particle migration in gap-graded soils

Evaluation of mechanical behaviour of gap-graded soils with particle property disparity

Coarse and Fine Particles and Daily Mortality in Nine French Cities

A rigid-walled ‘transparent soil’ permeameter has been developed to study visually the mechanisms occurring during seepage-induced internal erosion in susceptible granular media under upward flow. The experiments use borosilicate glass particles in place of soil, and an optically matched oil mixed with fluorescent dye in place of water. The technique known as plane laser-induced fluorescence (PLIF) enables a two-dimensional plane of particles and fluid to be viewed inside the permeameter, away from the walls. Results of tests have provided close agreement with those of other researchers on soil of comparable particle size grading. Unstable materials showed migration of fine grains under mean hydraulic gradients as low as i = 0·25, whereas stable materials eventually failed by heave at hydraulic gradients close to unity. Internally unstable soils where the loads were predominantly supported by the coarser fraction exhibited suffusion (fines migration without disruption of the load-bearing system); those supported by both coarse and fine particles exhibited suffosion (i.e. volume change during fines migration). Quantitative image analysis conducted on one unstable sample showed areas of open void space migrating through the sample at low hydraulic gradients near critical, as defined by Skempton and Brogan in 1994. This occurred before the externally measured local hydraulic gradients began to diverge significantly from the mean. The testing technique developed shows that optically matched glass and oil behave mechanically similarly to soil and water, and that the PLIF technique coupled with image analysis can provide an additional insight into the mechanisms of internal erosion.

Filling ability is one of the prominent rheological properties of the self-compacting concrete (SCC), which has been studied in this research work deploying the functional behavior of the concrete through the Orimet apparatus using the coupled ANSYS-SPH interface. Seven (7) model cases: Case 1: 0% coarse particles and 100% fine particles, Case 2: 60% coarse particles and 40% fine particles, Case 3: 55% coarse particles and 45% fine particles, Case 4: 50% coarse particles and 50% fine particles, Case 5: 45% coarse particles and 55% fine particles, Case 6: 40% coarse particles and 60% fine particles and Case 7: 100% coarse particles and 0% fine particles were studied and optimized. The maximum size of the coarse aggregates considered is 20 mm and that of the fine aggregates is below 4 mm. The Bingham model properties for the multiphysics (SPH)-ANSYS models’ simulation are; Viscosity = 20 ≤ μ ≤ 100 and the Yield stress = 50 [Formula: see text] standard flow time, t (s) ranges; 0 ≤ t ≤ 6, and the Orimet volume is 10 l. The minimum boundary flow time, which represents the time (0 ≤ t ≤ 6) it takes for the SCC to completely flow through a specified distance, typically measured in seconds was modeled for in the seven (7) model cases. The first case; 0%C mixed with 100%F flowed out completely in 6 s, second case; 40%C mixed with 60%F completely flowed out in 5 s, third case; 45%C mixed with 55%F completely flowed out in 9 s, fourth case; 50%C mixed with 50%F completely flowed out in 12 s, fifth case; 55%C mixed with 45%F completely flowed out in 11 s, sixth case; 60%C mixed with 40%F completely flowed out in 12 s, and lastly, the 7th case; 100%C mixed with 0%F completely flowed out in 20 s. The minimum flow time was considered alongside other relevant parameters and tests, such as slump flow, passing ability, segregation resistance, and rheological properties (stresses), to comprehensively assess the filling ability of SCC in this model. By considering these factors and the optimized mix (40%C + 60%F:5 s), engineers and researchers can optimize the SCC mix design to achieve the desired flowability and filling performance for their specific construction applications. The multiphase optimized mix (40%C + 60%F:5 s) was further simulated using the coupled interface of the ANSYS-SPH platform operating with the CFX command at air temperature of 25 °C, which incorporated the studied density of 2400 kg/m3, plastic viscosity boundary, yield stress, and aggregate sampling. The model simulation operated on total number of nodes = 143,083, total number of elements = 753,292, total number of tetrahedrons = 753,292, and total number of faces = 68,488, and produced Dynamic Viscosity = 1.831E-05 kg m−1 s−1, Thermal Conductivity = 2.61E-02 W m−1 K−1, Absorption Coefficient = 0.01 m−1, Thermal Conductivity = 2.61E-02 W m−1 K−1, Refractive Index = 1.0 m m−1, Molar Mass = 1 kg kmol−1, Specific Heat Capacity = 8.80E + 02 J kg−1 K−1, Normal Speed = 165 mm s−1, Pressure Profile Blend = 0.05, and Maximum Partition Smoothing Sweeps = 100. Also, the Global Length = 1.9144E-01, Minimum Extent = 1.1800E-01, Maximum Extent = 6.5976E-01, Density = 1.1850E + 00, Velocity = 1.6500E-01, Advection Time = 1.1602E + 00, and Reynolds Number = 2.0443E + 03. The simulation also produced wall forces and moments on the wall of the Orimet for the optimized mix containing 40%C + 60%F:5 s flow mix as follows; pressure force on wall; −3.0996E-08, −2.0863E-07, and −3.5048E-04 for x-component, y-component, and z-component, respectively, viscous force on wall; −5.5332E-10, −9.2298E-10, and −2.7250E-05 for the x-, y-, and z-components, respectively, pressure moment on wall; −5.0051E-05, 3.1362E-06, and 2.2774E-09 for the x-, y-, and z-components, respectively and viscous moment on wall; −3.8925E-06, 2.4396E-07, and −7.2693E-11 for the x-, y-, and z-components, respectively. Also, the maximum residuals were located at node 110413 for the pressure, node 76766 for the K-TurbKE, and node 110724 for the E-Diss.K. Ideally, the mix, 40%C + 60%F:5 s has been proposed as the mix with the most efficient flow to achieve the filling ability for sustainable structural concrete construction.

BackgroundParticulate matter air pollution has been associated with adverse health effects. The fraction of ambient particles that are mainly responsible for the observed health effects is still a matter of controversy. Better characterization of the health relevant particle fraction will have major implications for air quality policy since it will determine which sources should be controlled.The RUPIOH study, an EU-funded multicentre study, was designed to examine the distribution of various ambient particle metrics in four European cities (Amsterdam, Athens, Birmingham, Helsinki) and assess their health effects in participants with asthma or COPD, based on a detailed exposure assessment. In this paper the association of central site measurements with respiratory symptoms and restriction of activities is examined.MethodsAt each centre a panel of participants with either asthma or COPD recorded respiratory symptoms and restriction of activities in a diary for six months. Exposure assessment included simultaneous measurements of coarse, fine and ultrafine particles at a central site. Data on gaseous pollutants were also collected. The associations of the 24-hour average concentrations of air pollution indices with the health outcomes were assessed in a hierarchical modelling approach. A city specific analysis controlling for potential confounders was followed by a meta-analysis to provide overall effect estimates.ResultsA 10 μg/m3 increase in previous day coarse particles concentrations was positively associated with most symptoms (an increase of 0.6 to 0.7% in average) and limitation in walking (OR= 1.076, 95% CI: 1.026-1.128). Same day, previous day and previous two days ozone concentrations were positively associated with cough (OR= 1.061, 95% CI: 1.013-1.111; OR= 1.049, 95% CI: 1.016-1.083 and OR= 1.059, 95% CI: 1.027-1.091, respectively). No consistent associations were observed between fine particle concentrations, nitrogen dioxide and respiratory health effects. As for particle number concentrations negative association (mostly non-significant at the nominal level) was observed with most symptoms whilst the positive association with limitation of activities did not reach the nominal level of significance.ConclusionsThe observed associations with coarse particles are in agreement with the findings of toxicological studies. Together they suggest it is prudent to regulate also coarse particles in addition to fine particles.

Microscopic mechanism of the combined effects of confining pressure and fines content on suffusion in gap-graded underfilled soils

Number concentration, size distribution and fine particle fraction of tropospheric and stratospheric aerosols

Experimental investigation of segregation in a rotating drum with non-spherical particles

The growing environmental concern over waste tire accumulation necessitates innovative recycling strategies in construction materials. Therefore, this study aims to develop and evaluate sustainable concrete by integrating waste tire rubber (WTR) aggregates of different sizes and recycled waste tire steel fibers (WTSFs), assessing their combined effects on the mechanical and microstructural performance of concrete through experimental and analytical approaches. WTR aggregates, consisting of fine (0–4 mm), small coarse (5–8 mm), and large coarse (11–22 mm) particles, were used at substitution rates of 0–20%; WTSF was used at volumetric dosages of 0–2%, resulting in a total of 40 mixtures. Mechanical performance was evaluated using density and pressure resistance tests, while microstructural properties were assessed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The findings indicate systematic decreases in density and compressive strength with increasing WTR ratio; the average strength losses were approximately 12%, 20%, and 31% at 5%, 10%, and 20% for WTR substitution, respectively. Among the WTR types, the most negative effect occurred in fine particles (FWTR), while the least negative effect occurred in coarse particles (LCWTR). The addition of WTSF compensated for losses at low/medium dosages (0.5–1.0%) and increased strength by 2–10%. However, high dosages (2.0%) reduced strength by 20–40% due to workability issues, fiber clumping, and void formation. The highest strength was achieved in the 5LCWTR–1WTSF mixture at 36.98 MPa (≈6% increase compared to the reference/control concrete), while the lowest strength was measured at 16.72 MPa in the 20FWTR–2WTSF mixture (≈52% decrease compared to the reference/control). A strong positive correlation was found between density and strength (r, Pearson correlation coefficient, ≈0.77). SEM and EDX analyses confirmed the weak matrix–rubber interface and the crack-bridging effect of steel fibers in mixtures containing fine WTR. Additionally, a hybrid prediction model combining physics-informed neural networks (PINNs) and CatBoost, supported by data augmentation strategies, accurately estimated compressive strength. Overall, the results highlight that optimized integration of WTR and WTSF enables sustainable concrete production with acceptable mechanical and microstructural performance.

The relative importance of local and regional sources of lead and associated elements in fine and coarse aerosol particles of an urban atmosphere was assessed by means of a two-day study, July 20 and 30, 1980 in Beijing, China. Five near-ground locations were selected for aerosol sampling by cascade impactors and elemental analysis by proton induced X-ray emission (PIXE): the imperial palace courtyard, a park, near two streets, and a mid-street traffic island. These sites, ranked in order of increasing traffic intensity and fugitive surface dust, showed that concentrations of major dust constitutents, represented by coarse particle (>2 μm diameter) Si, Al, and Ca, increased correspondingly. Pb, as well as Zn, As, and Cu, were present mainly in fine (<2 μm) particles; their concentrations were unrelated to traffic, indicating they resulted mainly from regional combustion or other sources. However, these elements also were present in coarse particles at concentrations that varied with the major dust elements and were relatively enriched, compared to average earth crust rock material, by factors of more than 100 (Pb), 50 (Zn), and 10 (Cu). Nonurban Beijing shows much smaller coarse aerosol enrichments of Pb, Zn, and Cu, indicating urban contamination of surface dust. Published data from St. Louis, USA show both fine and coarse aerosol Pb and Zn. Compared with Beijing, fine and coarse concentrations in St. Louis are similar for Pb, but lower for Zn, Ca, and Fe. Both Pb and Zn are enriched relative to earth crust composition to a greater degree in St. Louis than Beijing in both fine and coarse particle size ranges. The results suggest that heavy metals from combustion occur in the air as fine particles and, after deposition on the surface, as reentrained coarse particles of fugitive dust. Both many contribute to human exposures of these heavy metals.

Samples of size-fractionated PM10 (airborne particulate matter with aerodynamic diameter less than <TEX>$10\mu\textrm{m}$</TEX>) were collected at an urban site in Jeju city from May to September 2002. The mass concentration and chemical composition of the samples were measured. The data sets were then applied to the CMB receptor model to estimate the source contribution of PM10 in Jeju area. The average PM10 mass concentration was 28.80<TEX>$\mu\textrm{g}/m^3$</TEX> (<TEX>$24.6~33.49\mu\textrm{g}/m^3$</TEX>), and the FP (fine particle with aerodynamic diameter less than <TEX>$2.l\mu\textrm{m}$</TEX> fraction in PM10 was approximately 8% higher than the CP (coarse particle with aerodynamic diameter greater than <TEX>$2.l\mu\textrm{m}$</TEX> and less than <TEX>$10\mu\textrm{m}$</TEX> fraction in PM10. The CP composition was obviously different from the FP composition, that is, the most abundant water soluble species was nitrate ion in the FP, but sulfate ion in the CP. Also sulfur was the most dominant element in the FP, however, sodium was that in the CP. From CMB receptor model results, it was found that road dust was the largest contributor to the CP mass concentration (45% of the CP) and ammonium nitrate, domestic boiler, and marine aerosol were major sources to the CP mass. However, the secondary aerosol was the most significant contributor to the FP mass concentration (45% of the FP). In this study, it was suggested that the contributions of soil dust and gasoline vehicle became very low due to collinearity with road dust and diesel vehicle, respectively.

Versatile aerosol concentration enrichment system (VACES) for simultaneous in vivo and in vitro evaluation of toxic effects of ultrafine, fine and coarse ambient particles Part II: Field evaluation

Distribution patterns and characterization of outdoor fine and coarse particles