Variation Of Particle Size Distribution Research Articles

Sensitivity of Simulated GMI Brightness Temperatures to Variations in Particle Size Distributions in a Severe Hailstorm

AbstractGlobal Precipitation Measurement (GPM) Microwave Imager (GMI) brightness temperatures (BTs) were simulated over a case of severe convection in Texas using ground-based S-band radar and the Atmospheric Radiative Transfer Simulator. The median particle diameter Do of a normalized gamma distribution was varied for different hydrometeor types under the constraint of fixed radar reflectivity to better understand how simulated GMI BTs respond to changing particle size distribution parameters. In addition, simulations were conducted to assess how low BTs may be expected to reach from realistic (although extreme) particle sizes or concentrations. Results indicate that increasing Do for cloud ice, graupel, and/or hail leads to warmer BTs (i.e., weaker scattering signature) at various frequencies. Channels at 166.0 and 183.31 ± 7 GHz are most sensitive to changing Do of cloud ice, channels at ≥89.0 GHz are most sensitive to changing Do of graupel, and at 18.7 and 36.5 GHz they show the greatest sensitivity to hail Do. Simulations contrasting BTs above high concentrations of small (0.5-cm diameter) and low concentrations of large (20-cm diameter) hailstones distributed evenly across a satellite pixel showed much greater scattering using the higher concentration of smaller hailstones with BTs as low as ~110, ~33, ~22, ~46, ~100, and ~106 K at 10.65, 18.7, 36.5, 89.0, 166.0, and 183.31 ± 7 GHz, respectively. These results suggest that number concentration is more important for scattering than particle size given a constant S-band radar reflectivity.

Using multi-fractal and joint multi-fractal methods to characterize spatial variability of reconstructed soil properties in an opencast coal-mine dump in the Loess area of China

Opencast coal mining activities have significant effects on the reconstructed soil properties, including its physical, chemical and biological properties. To assess the effects of opencast mining and associated dumping activities on reconstructed soil properties, the spatial variability of soil properties, i.e., soil particle size distribution (PSD), organic matter (OM) and total nitrogen (TN), in an inner dump after dumping and before reclamation in Antaibao opencast coal-mine of Shanxi Pingshuo was analyzed using multi-fractal and joint multi-fractal methods. Soil samples at 78 sampling sites at the depths of 0–20 cm and 20–40 cm were collected using an auger. The singularity spectra of soil properties in the study area were analyzed, and three multi-fractal parameters (i.e., D1, D2 and ∆α) were calculated. The singularity spectra and multi-fractal parameters can quantitatively characterize the spatial variability of soil PSD, OM and TN. The variability of soil PSD, OM and TN at the depth of 20–40 cm was higher than that at the depth of 0–20 cm. At same soil depth, the sand and clay contents showed relatively high spatial variability, and the silt content, OM and TN exhibited relatively low spatial variability. The spatial variability in sand content, OM and TN between 0 and 20 cm and 20–40 cm depths had a relatively high correlation, while the clay and silt contents at the depths of 0–20 cm and 20–40 cm showed a relatively low correlation. Multi-fractal and joint multi-fractal methods exhibited more advantages in characterizing spatial variability of reconstructed soil properties. This study provided a theoretical basis for the soil sampling optimization of in the opencast coal-mine dump in the Loess area of China.

Near infrared spectroscopy for rapid and in-line detection of particle size distribution variability in lactose during mixing

Particle size distribution (PSD) variability in excipients may cause unacceptable prolongation of mixing time needed to achieve blend homogeneity. Therefore, it is vital to modulate mixing through real-time monitoring of PSD variability. Notwithstanding the criticality of PSD variability, real-time measurement of PSD during mixing is relatively unexplored; and this is the focus of the present study. The model excipient was commercial grade lactose with modified PSD that conformed to the manufacturer’s specifications. It was mixed with microcrystalline cellulose and chlorpheniramine in a double-cone blender. High and low dose blends were prepared and near infrared spectroscopy (NIRS) was used to collect spectral data, during mixing, for chemometric modelling of PSD. Four modelling approaches based on partial least squares regression (PLSR) were applied. The models were highly interpretable and rapidly measured PSD near the beginning of mixing (5th to 6th rotation), with accuracy (relative standard error of prediction <5.0%, r2 ≈ 1.00, slope ≈ 1.00). Therefore, NIR chemometric modelling is a viable strategy to detect variability in PSD of excipients during blending and could enable real-time control of mixing. Most significantly, this strategy is potentially transferable to the monitoring and controlling of batch and continuous processes, where PSD is either a source of process variability or a critical quality attribute.

Investigating the effect and mechanism of particle size distribution variability on mixing using avalanche testing and multivariate modelling

Particle size distribution (PSD) variability in excipients is widely thought to affect the mixing process and the achievement of blend homogeneity. Yet, few studies have addressed this issue by attempting to ascertain the relationship and elucidate its mechanism. To address this, the model material, lactose, was modified to reflect commercially relevant PSD variations and mixed with microcrystalline cellulose and chlorpheniramine in a double-cone blender. Multivariate modelling and avalanche testing were applied to elucidate the relationship and mechanism. PSD variability can cause significant change in mixing time, by 8 times and 3 times (p ≈ 0.00) for high and low dose drug formulations, respectively. Achievement of blend homogeneity depended on the dispersive mixing mechanism (r2 = 0.99). Dispersive mixing was adversely affected by powder cohesiveness and powder dilation, which increased as the proportion of fine particles in lactose powder increased. This study yielded three conclusions. Firstly, PSD variability in pharmaceutical grade excipients can cause unacceptable prolongation in mixing time. Secondly, the impact of PSD variability on continuous mixing and other batch mixing of various scales, requires investigation. Lastly, the current findings can contribute to the development of robust mixing operations in the form of offline pre-emptive measures and inline process control strategies.

CFD and physical models of PM separation for urban drainage hydrodynamic unit operations

A hydrodynamic separator (HS) is a common pre-treatment unit operation (UO) for separating coarser particulate matter (PM). While HS designs have disparate internal geometries, surface areas, and volumes; for a given PM granulometry this study hypothesizes there are limits to PM separation. In this study, a large group of full-scale HS units were tested with physical and computational fluid dynamics (CFD) models to evaluate HS functionality based on surface overflow rate (SOR), HS geometrics (diameter, height, baffling), PM granulometry, particle size distribution (PSD), turnover volume, hydraulic capacity, and short-circuiting. Models were loaded with a hetero-disperse PSD, a common testing metric. PM separation results show that PSD variability greater than ±2% from this metric are different (α = 0.05). Comparing PM separation using the PSD metric across the SOR range: (1) all HS results were below the ideal SOR model, (2) above Hazen's tanks-in-series model with N = 1, (3) above plain tank designs, and (4) declined logarithmically in a ±10% range. Integrated across a triangular loadgraph, the SOR model significantly over-estimated PM separation for all HS units. The SOR model deviated from the validated CFD model, as PSD loadings became increasingly mono-disperse. A validated CFD model is shown to be a valuable tool to examine HS design and functionality.

The role of gangue on the mitigation of mining-induced hazards and environmental pollution: An experimental investigation

Gangue, produced from coal mining and washing process, is a serious threat to the ground environment. Gangue backfilling mining method can solve this problem and reduce mining-induced hazards, e.g., controlling surface subsidence and preventing water inrush from seeping into goaf by cracks in overlying strata. In this paper, effects of the original particle size distribution (PSD) and water content on the particle crushing behavior and seepage properties of granular gangues were investigated. Experimental results show that the crushing behavior can promote the compaction of gangue particles; the variation of PSD after crushing reveals distinct fractal characteristics. With the increasing compression stress, the particle crushing ratio and fractal dimension increase, while the permeability decreases. Due to the rearrangement of particles and newly generated fine particles filled the gap among larger particles, it is difficult to reduce the permeability by increasing the compressive stress. In addition, the variation of fractal dimensions is similar to the crushing ratio, so the particle crushing can be illustrated by fractal dimensions. The relationship between porosity and permeability established by the Kozeny-Carman equation can model the effect of particle crushing in this research. The reliability of the equation is verified by the comparison of model result and experimental data. To increase the mitigation rate of mining-induced hazards and environmental pollution by GBM method, granular gangues can be crushed into smaller particles and dehydrated before backfilling.

The feasibility of predicting the spatial pattern of soil particle-size distribution using a pedogenesis model

Particle-size distribution (PSD) plays an important role in influencing a number of soil physical, chemical, and biological properties. Currently, digital soil mapping (DSM) methods based on empirical observations have been widely used in mapping PSD. However, DSM methods rarely consider soil genetic processes. This paper investigated the use of a mechanistic soil evolution model, State Space Soil Production and Assessment Model (SSSPAM), to simulate the spatiotemporal evolution of PSD in the Hunter Valley, NSW, Australia. SSSPAM simulates the spatial and temporal variation of PSD within a landscape based on erosion due to overland flow, deposition, and physical weathering within the soil profile. We conducted a simulation over the 144 km2 area using a 30 m digital elevation model (DEM) as an input. The model simulated soil evolution over 70,000 years to ensure that the PSD had reached steady-state. To validate and analyze the influence of different process parameters on particle size dynamics, we carried out a parametric study in a field within the study area and found a strong relationship between runoff excess generation, exponential weathering rate, and soil particle-size distribution. As expected, higher discharge rates produced coarser particles and larger weathering rates produced finer PSD. We further explored the feasibility of combining the mechanistic SSSPAM and empirical DSM approaches by comparing simulation results with observed sand content. We found limitations of the SSSPAM model to predict sand fraction accurately in the study area due to incomplete process coverage. The output of SSSPAM can be improved by integrating it with DSM techniques. Overall, SSSPAM can explore how particle size will change through time and identify areas with risks of erosion and deposition. Such a model can be used to inform large-scale management to ensure our soil is secured in the future.

Characterizing the spatial variability of soil particle size distribution in an underground coal mining area: An approach combining multi-fractal theory and geostatistics

Long-term underground coal mining activities results in severe surface deformation and land subsidence, altering soil physical properties significantly. Soil particle size distribution (PSD) is a fundamental physical attribute affecting many other soil properties. Therefore, understanding the variability of PSD is crucial to conduct targeted land rehabilitation. In present study, a novel method combining multi-fractal theory and geostatistics was advanced to characterize the spatial variability of soil PSD in a coal-mined subsidence area. Three independent field plots, i.e., one unmined plot (UMP), one subsided plots (SUP), and one reclaimed plot (RCP), in NO.3 Pingshuo Anjialing underground coal-mine in Shanxi province of China, were selected to perform this study. Four multi-fractal attributes of PSD of individual soil samples, i.e., D(0), D(1), Δα(q) and Δf(α), in three plots were calculated, and geo-statistics was employed to quantify the spatial variability of multi-fractal attributes of PSD. This combining method showed some advantages in characterizing the variability of soil PSD compared to single multi-fractal, single geo-statistics or traditional statistics, and it can characterize the spatial variability of overall PSD characteristics in detail, quantifying the spatial variability of soil PSD range, PSD concentration degree, PSD non-uniformity, and PSD non-symmetry. The soil PSD range, PSD concentration degree, PSD non-uniformity and PSD non-symmetry in this underground coal mining area didn't present a high spatial variability. Combining multi-fractal theory and geostatistics is an effective method to characterize the spatial variability of soil PSD in underground coal-mine area, and this method is universal and can be popularized and applied in other unmined areas.

Measurement of static and dynamic properties of municipal solid waste at Mavallipura landfill site, India

Municipal solid waste (MSW) landfills have been widely constructed around the world for proper dispose of MSW. Geotechnical properties of MSW are difficult to determine because the heterogeneity, wide variation in particle size distribution and time dependent degradation. Knowledge of geotechnical properties of MSW is essential for the design and operation of landfills. Geotechnical properties of the MSW from landfills is very limited. The design of MSW landfills requires the selection of representative MSW material properties. Static and dynamic properties of emplaced MSW from landfill sites at Bangalore, India are evaluated. A comprehensive field and laboratory studies are conducted on MSW disposed at Mavallipura landfills that are in operation for about 12 years. Laboratory studies included: waste composition, water content, hydraulic conductivity, shear behavior for evaluation of static MSW properties. Field measurements included: cyclic plate load test and geophysical testing (multichannel analysis of surface waves) to assess the dynamic MSW properties at landfill site. Also, results obtained from cyclic plate load test is compared with numerical simulation like PLAXIS 2D. In additional, this paper presents a method for extrapolation of Vs30 for MSW site where subsurface data does not extend to a depth of 30 m. Based on the detailed field and laboratory test data, characterization of the small strain shear modulus and the shear wave velocity of MSW is an integral component of various seismic analyses, including site classification, analysis seismic response of landfill. The results in this study will provide guidance in the design and operation of the landfills in India.

Influence of Particle Size Distribution of High Calcium Fly Ash on HVFA Mortar Properties

This study evaluates the effect of particle size distribution (PSD) of high calcium fly ash on high volume fly ash (HVFA) mortar characteristics. Four PSD variations of high calcium fly ash used were: unclassified fly ash and fly ash passing sieve No. 200, No. 325 and No. 400, respectively. The fly ash replacement ratio of the cementitious material ranged between 50-70%. The results show that with smaller fly ash particles size and higher levels of fly ash replacement, the workability of the mixture was increased with longer setting time. There was an increase in mortar compressive strength with finer fly ash particle size, compared to those with unclassified ones, with the highest strength was found at those with fly ash passing mesh No. 325. The increase was found due to better compactability of the mixture. Higher fly ash replacement reduced the mortar’s compressive strength, however, the rate was reduced when finer fly ash particles was used.

Expanding particle size distribution and morphology of aluminium-silicon powders for Laser Beam Melting by dry coating with silica nanoparticles

Current requirements for metal powder in Additive Manufacturing via Laser Beam Melting in powder bed (LBM) that ensure repeatably homogeneous thin layers can be spread and LBM products with high relative density ρrel can be built are high sphericity and particle size distributions (PSD) with limited share of fine particles. The most established LBM powder production method today is delicate and costly inert gas atomization. It yields highly spherical particles with continuous particle size distributions, but two thirds of the atomized powder exceed established LBM size ranges. A novel process route to improve flowability of cohesive metal powders is the coating of micro-sized powder particles with small amounts of nanoparticles. In this article, significant improvements in powder layer smoothness and ρrel of LBM samples are shown by statistical analysis of physical experiments on the example of Al-Si powders dry coated with 0.5 wt% nanoparticular fumed silica SiOx. This setup was chosen because Al is most prone to powder flowability issues in LBM and no new chemical elements are added to the alloy from dry coated SiOx. Particle shape is varied from spherical over ovoidal to irregular using powder atomized with Ar, N and air. Effects of variations of PSD and LBM parameters on ρrel, defect types, microstructure and hardness using powders with and without SiOx are investigated. Because ρrel are skewed towards 100%, ANOVA on ranks is the applicable statistical method. Since the principle of using nanoparticles as spacers between microparticles is based on geometry, it is transferrable to other material systems. This may help for example to increase ρrel of LBM metal matrix composites prepared by mechanical alloying as non-spherical particles with considerable amounts of fine particles. The use of larger percentages of atomized powders in LBM can increase resource efficiency.

Erodibility Characteristics of Three Geological Sediments in the Idah-Ankpa Plateau of the Anambra Basin, Nigeria

Three geological sediments, namely, the Upper Coal Measures (UCM), the Ajalli Sandstones (AS), and the Lower Coal Measures (LCM), underlie 100% of the landscape of the Idah-Ankpa Plateau (IAP) of the Anambra Basin, Nigeria. The total number of gullies in occurrence on the IAP formation has been estimated at 740, 100, and 1 for AS, UCM and LCM respectively. A total of 34 samples were randomly collected from gully side walls at a depth range of 0 – 15 cm. At sites where gullies did not exist, sampling pits were dug up to a depth of 15 cm within which samples were collected. Fifteen samples were collect from the AS, 14 from the UCM, and 5 from the LCM. Particle size distribution was determined by the hydrometer method, and the dry bulk density was computed from undisturbed cores after weighing, drying at 105oC, and reweighing. The two sets of data were analyzed using descriptive statistics. Results show that the AS had a mean % sand plus %silt = 95, %clay = 5, and a mean dry bulk density = 1.31 g/cm3; the UCM had values of 80, 20, and 1.57 g/cm3; and the LCM 61, 39, and 1.71 g/m3 respectively. The data indicate that the AS sediments are the most prone to detachment and transport, followed by the UCM. Therefore, the vulnerability of the sediments to erosion can be ranked as AS&gt;UCM&gt;LCM, and this can be attributed to their wide variations in particle size distribution and dry bulk density. The findings also agree with the order of proliferation of gullies on the IAP. Activities that trigger accelerated erosion on the AS should be controlled.

The QMOM Method to Solve The PBE Equations of the Urban Haze

Mega and medium-sized cities in China are facing the increasingly serious aerosol pollution, among them Xi’an is one of the typical cities. During the early stage of ash haze, aerosol concentration is rising so fast that the simulation of the process is difficult. This article uses the population balance equation (PBE) describing the distribution of fine particles, and solves the changing process of particle size distribution by the moment method. Population balance equation, a non-linear hyperbolic equation about number density function, is employed to describe micro-behaviors (aggregation, breakage, growth) of disperse phase and resulting variation of particle size distribution. By expressing PBEs for both batch and continuous operations in a general form, and using weighted residual method to derive the moment equations, different moments can be tracked directly. Three examples of simulation results show that compared with the analytical solution, relative error of this method is within 10−5 and has the characteristics of high precision and low computation amount. In early 2016, the early stage of PM2.5 pollution in Xi’an is simulated and the simulation results and experimental results are highly consistent.

Study of the Structural and optical properties of Pure and Sn doped Polyaniline hydrochloride polymer (PANI) thin films prepared by Spin coating method

In this study the structural and optical properties of pure and Sn doped films polyanilinehydrochloride (PANI) doped by Tin (Sn) with volumetric percentages (3, 6, and 9)%, which prepared by using the spin coating method on substrates of the glass at room temperature. The structural properties of the prepared films were studied by x-ray diffraction technique. The results illustrate amorphous structure .The atomic force microscope (AFM) diagnosis has led the doping process to decrease in the roughness of the surface and the average rate of the square root with the variation in particle size distribution. The study of the optical properties by measuring then absorption and transmission spectra as a function of wavelength (320-910) nm to the pure and doped film of PANI, the results showed that the transmittance decreased with increasing doping due to the increase in the impurity resulted which makes attenuation in the intensity of incident light with a increasing of absorption. The results also showed that the polymer has an indirect allowed energy gap and it decrease with increasing doping because of the doping levels (Sn) inside the optical energy gap.

Rheological behavior of water-ash mixtures from Sakurajima and Ontake volcanoes: implications for lahar flow dynamics

Lahars represent one of the most serious volcanic hazards, potentially causing severe damage to the surrounding environment, not only immediately after eruption but also later due to rainfall or snowfall. The flow of a lahar is governed by volcanic topography and its rheological behavior, which is controlled by its volume, microscale properties, and the concentration of particles. However, the effects of particle properties on the rheology of lahars are poorly understood. In this study, viscosity measurements were performed on water-ash mixtures from Sakurajima and Ontake volcanoes. Samples from Sakurajima show strong and simple shear thinning, whereas those from Ontake show viscosity fluctuations and a transition between shear thinning and shear thickening. Particle analysis of the volcanic ash together with a theoretical analysis suggests that the rheological difference between the two types of suspension can be explained by variations in particle size distribution and shape. In particular, to induce the complex rheology of the Ontake samples, coexistence of two particle size groups may be required since two independent behaviors, one of which follows the streamline (Stokes number St << 1, inertial number I < 0.001) and the other shows a complicated motion (St ~ 1, I ~ 0.001), compete against each other. The variations in the spatial distribution of polydisperse particles, and the time dependence of this feature which generates apparent rheological changes, indicate that processes related to microscale particle heterogeneities are important in understanding the flow dynamics of lahars and natural polydisperse granular-fluid mixtures in general.

Effect of the micro-flocculation stage on the flocculation/sedimentation process: The role of shear rate

Dynamic analysis on the variation of particle size distribution (PSD) and the fractal characteristics of PSD (Df) were investigated to better understand the continuous procedure of the floc growth and optimize the control of flocculation process. It was found that the flocculation process could be divided into three stages, i.e., the micro-flocculation stage, the growth stage and the steady (or breakage) stage. As the stage which is crucial to the morphology of micro-flocs (the building blocks of large flocs), the micro-flocculation stage plays an important role on flocculation/sedimentation process. The results showed that an increase in shear rate (11s−1<G<30s−1) during the micro-flocculation stage contributed to micro-flocs with larger size and more compact structure. As shear rate further increased (30s−1<G<55s−1), the micro-floc average size gently decreased from 13.61μm to 10.91μm, whereas two-dimension fractal dimension of micro-flocs gradually increased from 1.85 to 1.89. This indicated that further increase of shear rate during the micro-flocculation was incline to the formation of smaller micro-flocs with more compact structure. According to the results of final floc properties, the moderate shear rate (G=30s−1) benefited to the micro-floc formation to form final flocs with desired properties, further improved the treatment efficiency in the whole process. Based on the kinetics in the micro-flocculation stage, a conceptual model was proposed to describe the micro-floc growth under different shear rates, further revealed the reason for the different properties of final flocs under various shear rate during the micro-flocculation stage. Combining the results with model, it was concluded that shear rate during the micro-flocculation stage mainly affected final flocs by the domination of micro-floc structure. This research gives indications both for theoretical and actual works to improve the efficiency in the solid/liquid process.

Determination of hand soil loading, soil transfer, and particle size variations after hand-pressing and hand-mouthing activities

Hand-pressing trials and hand-to-mouth soil transfer experiments were conducted to better understand soil loadings, soil transfer ratios for three mouthing activities, and variations in particle size distributions under various conditions. Results indicated that sand caused higher soil loadings on the hand than clay. When the moisture level of clay soil exceeded its liquid limit, soil loadings also increased. Greater pressing pressures also led to larger clay loadings. Clay with a moisture content close to its plastic limit caused the smallest soil loadings due to strong soil cohesion. Particle sizes of the transferred clay were larger than that of the original clay, indicating that hand-pressing and the pressure exerted may have enhanced clay particles of larger sizes adhering onto the hand. Nevertheless, the sizes of most particles that adhered to the hand were still smaller than 150 μm. Higher pressing pressures and greater moisture contents resulted in larger soil loadings on the hand, and transfer ratios became smaller. Transfer ratios from palm-licking with clay particles were smaller than those from finger-mouthing, which may have been due to finer particles that more readily adhered to the skin of the palm and that were transferred from the hand to the mouth with greater difficulty.

Variations of Particle Size Distribution, Black Carbon, and Brown Carbon during a Severe Winter Pollution Event over Xi’an, China

Real-time particulate matter (PM) size distributions, 4-hour time resolution, PM2.5, carbonaceous materials, and their optical properties were measured during a severe pollution event in Xi’an, China. High PM2.5/PM10 ratios were observed on both pollution (0.83) and non-pollution (0.73) days, emphasizing the abundance of fine particles during sampling days. The particle number (PN) first peaked with a wide size range (30–100 nm) before morning rush hours (approximately 01:00–05:00) on pollution and non-pollution days, demonstrating that PN was governed by the accumulation of freshly emitted diesel particles and characterized by distinct aerosol condensation growth. By contrast, the second peak time and size range differed between pollution and non-pollution days because of different formation mechanisms. The light-absorbing coefficients of both black carbon (BC, babs-880nm, BC) and brown carbon (BrC, babs-370nm, BrC) were high on pollution days and decreased to approximately half of those values on non-pollution days, indicating that the degree of light absorption is reduced by rain. The diurnal variation in babs-880nm, BC pollution peaked with traffic on January 1 and 2. By contrast, it remained in relatively stable and high ranges (120–160 Mm–1) in the second period (January 3–5) without traffic peaks, illustrating that the dominant sources changed even during the same pollution period. High values of both babs-370nm, BrC and babs-880nm, BC coincided in the afternoon and evening due to emissions from primary sources, and abundant aqueous secondary organic carbon, respectively. A highly variable mass absorption coefficient of BrC also indicated the variety of fuel combustion sources of primary BrC in Xi’an.

Experimental Investigation on Hydraulic Properties of Granular Sandstone and Mudstone Mixtures

The caved zone during longwall mining has high permeability, resulting in a mass of groundwater storage which causes a threat of groundwater inrush hazard to the safe mining. To investigate the hazard mechanism of granular sandstone and mudstone mixture (SMM) in caved zone, this paper presents an experimental study on the effect of sandstone particle (SP) and mudstone particle (MP) weight ratio on the non-Darcy hydraulic properties evolution. A self-designed granular rock seepage experimental equipment has been applied to conduct the experiments. The variation of particle size distribution was induced by loading and water seepage during the test, which indicated that the particle crushing and erosion properties of mudstone were higher than those of sandstone. Porosity evolution of SMM was strongly influenced by loading (sample height) and SP/MP weight ratio. The sample with higher sample height and higher weight ratio of SP achieved higher porosity value. In particular, a non-Darcy equation, for hydraulic properties (permeability κ and non-Darcy coefficient ζ) calculation, was sufficient to fit the relation between the hydraulic gradient and seepage velocity. The test results indicated that, due to the absence and narrowing of fracture and void during loading, the permeability κ decreases and the non-Darcy coefficient ζ increases. The variation of the hydraulic properties of the sample within the same particle size and SP/MP weight ratio indicated that groundwater inrush hazard showed a higher probability of occurrence in sandstone strata and crushed zone (e.g., faults). Moreover, isolated fractures and voids were able to achieve the changeover from self-extension to interconnection at the last loading stage, which caused the fluctuation tendency of κ and ζ. Fluctuation ability in mudstone was higher than that in sandstone. The performance of an empirical model was also investigated for the non-Darcy hydraulic properties evolution prediction of crushing and seepage processes. The predictive results indicated that particle crushing and water erosion caused the increase of hydraulic properties, being the main reason that the experimental values are typically higher than those obtained from the predictive model. The empirical model has a high degree of predictive accuracy; however, κ has a higher predictive accuracy than ζ. Furthermore, the predictive accuracy of κ increases and ζ decreases with increasing weight ratio of SP.

Physical and Compaction Properties of Granular Materials with Artificial Grading behind the Particle Size Distributions

Granular materials in geotechnical engineering is generally considered to be mixtures of clay, sand, and gravel that commonly appear in slopes, valleys, or river beds, and they are especially used for the construction of earth‐rock‐filled dams. The complexity of the constitution of granular materials leads to the complexity of their properties. Particle size distribution (PSD) has a great influence on the strength, permeability, and compaction behavior of granular materials, and some implicit correlation may exist between the PSD and the compaction properties of granular materials. Field testing and statistical analysis are used to study the physical and compaction properties of granular materials with artificial grading behind the particle size distributions. The statistical properties in PSD of dam granular materials and how the variation of PSD renders statistical constant are revealed. The statistical constants of three types of dam granular materials are 2.459, 2.475, and 2.499, respectively, on average. These statistical constants have a positive correlation with dry density and a negative correlation with moisture content. According to this characteristic and little deviation between two different calculation methods (from grading analysis and based on the Weibull distribution), the presentation of the statistical analysis ensures the validity of the Weibull function’s description of the granular materials with artificial grading. After fitting the Weibull function to the PSD curve, the relationship between the Weibull parameters and the compaction degree in different soil samples is consistent with that in different types, providing guiding significance for evaluating and selecting dam granular materials.