Sieve Test Research Articles

Isotherm adsorption characteristics of carbon microparticles prepared from pineapple peel waste

The objective of this study was to investigate isotherm adsorption of carbon microparticles from pineapple peel waste. Carbon microparticles were prepared by carbonizing pineapple peel waste at 215-250°C and grinding using a saw-milling process. To investigate adsorption properties of carbon microparticles, experiments were done by evaluating adsorption of curcumin (as a model of adsorbate) in the ambient temperature and pressure under constant pH condition. To confirm the adsorption characteristics, carbon particles with different sizes (i.e., 100, 125, and 200 ?m) were tested, and the adsorption results were compared with several standard isotherm adsorption models: Langmuir, Freundlich, Temkin, and Dubinin- Radushkevich. To support the adsorption analysis, several characterizations (i.e., optical microscope, sieve test, and Fourier transform infrared analysis) were conducted. The adsorption test showed that the adsorption profile is fit to the Freundlich model for all variations, indicating the multilayer adsorption process on heterogeneous surfaces and interactions between adsorbate molecules. The results from other isotherm models also confirmed that the adsorption process occurs physically via Van der Waals force in binding adsorbate on the surface of adsorbent.

Comparisons between Geotextile Pore Sizes Obtained from Capillary Flow And Dry Sieving Tests

Abstract In the United States of America, two standard methods of measuring the largest pore size of a geotextile have been accepted: Dry Sieving Test (ASTM D4751, Standard Test Methods for Determining Apparent Opening Size of a Geotextile) and Capillary Flow Test (ASTM D6767, Standard Test Method for Pore Size Characteristics of Geotextiles by Capillary Flow Test). Despite several drawbacks of Dry Sieving Tests, such as the amount of time required; tendency of glass beads to become trapped, including trapping of glass beads inside the geotextiles; likelihood of imprecise preparation of glass beads; and potential electrostatic effects, the largest pore size (apparent opening size [AOS], O95) results obtained from Dry Sieving Test still determines many filtration criteria. Although the Capillary Flow Test was approved in 2002, it is still not widely adopted, despite the fact that it provides the largest pore size (Bubble Point, O98) and a complete pore size distribution of a geotextile. Decades of analyses searched for a correlation between the Dry Sieving and Capillary Flow Test results; however, none of them have been widely accepted because of the limited number of geotextiles used and a lack of proper calibration. The current study investigates a possible correlation between the Dry Sieving and Capillary Flow Test results with 51 woven, nonwoven, and composite geotextiles. The Capillary Flow Porometer was calibrated using four thin metal plates with known pore openings and two membranes. This study describes the challenges experienced during the Capillary Flow Test and factors affecting the test results. One finding is that the cleaning of calibration materials and equipment with Methanol plays an important role in the Capillary Flow Test results. The use of different shape factors, contact angles, and wetting liquids in the analyses are also considered. The outliers of Capillary Flow Test results were removed from the analysis using a box plot and whisker diagram, and a good correlation between AOS and Bubble Point (R2 = 0.78) was established.

Bankfull discharge estimation for Fishpot Creek

Abstract: Fishpot Creek has been investigated and bankfull discharge was calculated based on the collected data points obtained from 3D laser scanning of the stream. This report consists of two major parts. One is the 3D scanning and analysis the results, other part includes sampling of both bed and bank materials. In the first part, essential parameters of roughness coefficient based on Cowan’s method were calculated as well as calculating the cross-sectional area and wetted perimeter based on the profile obtained from stream channel scanning. Leica Scan Station HDS 3000 scanner was used to visualize the cross-sectional shape of the stream based on a high-density scan technology and finally applied to the manning’s equation to calculate the bankfull discharge. for sampling part both bed and bank materials were analyzed in lab, mechanical sieve test performed to investigate the gradation of bed and banks materials within the study area.

A new tool for conjunction analysis of ISRO's operational satellites, Close Approach Prediction Software: CLAPS

During the lifetime of an operational spacecraft, a situation may occur when it faces a close approach with other orbiting space objects. The mitigation strategy for minimizing threat from orbiting space objects is to first carry out proximity analysis for operational spacecraft's (primary) with all other catalogued orbiting space objects (secondary). In case of a possible close approach, to plan an evasive collision avoidance maneuver. The ever-increasing number of space objects around the Earth demands this kind of analysis on daily basis by satellite operators. Presently, ISRO is operating close to 50 satellites in LEO and GEO/GSO orbits and this number is increasing each year at a rapid rate. At present the NORAD TLE catalogue consists of more than 18000 unclassified space objects. The large number of object pairs require enormous amount of computational load to do such kind of analysis on daily basis. Therefore, an efficient and user-friendly tool to predict the future close approaches is necessary for satellite operators.In this paper, methodology is designed and developed for carrying out conjunction analysis for all operational satellites with catalogued space objects. In the design, efficient approach is adopted to reduce the computation time. Each object pair goes through screening process using pre-filters like perigee-apogee test and smart sieves. These filters are based on basic flight dynamics rules. Only those pairs which are passed by all filters are subjected to relative distance function method for finer assessment. For the candidate pairs which violate the specified minimum Inter-Satellite-Distance (ISD) limit, collision probability is computed. For operational satellites, latest available orbit determination results at control centre are used and orbit propagation is done with high fidelity ephemeris model. Orbit propagation of catalogued objects with TLE is done using SGP4 model. Using this design methodology, Close Approach Prediction Software (CLAPS) is developed in C++ language, to predict the future close approaches for multiple operational satellites with complete TLE catalogue in single run.CLAPS s/w is tested for various close encounter cases and results are validated with STK's AdvCAT tool. The close approach time and minimum distance are found to match up to millisecond and millimetre level respectively. The results of few actual close approach scenarios are presented and discussed. CLAPS is being used regularly at ISRO's Master Control Facility, Hassan for routine monitoring of close approaches.

Geotechnical properties of recycled construction and demolition materials for filling applications

Abstract Modern societies make a hard effort to improve the sustainability of resources due to enhanced environmental sensitivities in nowadays. This paper investigates the usability of recycled construction and demolition materials as an alternative to virgin aggregates in geotechnical applications such as the filling. The physical and geotechnical properties of recycled construction and demolition materials were determined by laboratory tests (i.e. sieve test, flatness test, Los Angeles abrasion test, water absorption test, pycnometer test, modified compaction test, California bearing ratio test, unconfined compressive strength test and resilient modulus test) and a comprehensive laboratory evaluation was carried out. Moreover, similar tests were conducted with a type of high-quality virgin aggregate material frequently used in fillings. The results of the tests conducted on construction and demolition materials were compared with results of the tests conducted on both virgin aggregate and different recycled aggregates which are accepted as an alternative to virgin aggregates used in the filling in the literature. Results of the tests conducted on construction and demolition materials were also evaluated according to the limit values in technical specifications of highway administrations of various countries. As a result of this study, it has been concluded that construction and demolition materials can be a good alternative to virgin aggregate used in the filling provided that it is taken measure against excessive water absorption value.

Experimental Study on Physical and Mechanical Properties of Mixed Filling behind Retaining Wall

Through large-scale triaxial shear test and particle sieving test, the particle breakage characteristics and shear strength of mixed coarse-grained fillers behind a high filling wall in Guizhou Province were studied. The effects of mudstone content, particle gradation, relative density and stress state of coarse-grained mixed fillers on particle breakage and shear strength were analyzed. With the increase of mudstone content, gradation and relative density, the particle breakage rate decreases. With the increase of confining pressure and stress, the particle breakage rate of coarse-grained soil also increases. The shear strength cohesion increases first and then decreases with the increase of mudstone content, and the internal friction angle decreases gradually. With the improvement of particle size distribution and the increase of relative density, the cohesion and internal friction angle increase. At the same time, a multivariate non-linear regression model was established to synthesize the comprehensive internal friction angle. The predicted values were in agreement with the experimental data, and the optimum mixed packing parameters were selected.

Stabilization of Baiji Sand Dunes by Petroleum Residues

This research is concerned with the use of petroleum residues to stabilize Baiji sand dunes. The purpose of this research is to study the stabilizing effect of these residues irrespective of their possible toxicity to plant and environment. Two petroleum mixtures were prepared in different mulching rates to test their efficiency in stabilizing sand dunes. Those mixtures were added to the dune samples with variable mulching rates, mixtures temperatures and initial water contents. Mechanical stability was estimated from percent of dry aggregates greater than 0.84 mm and percent of aggregates less than 0.42 mm. The mixtures of petroleum residues used in this study were found to be effective in forming large amounts of nonerodible aggregates greater than 0.84 mm and reducing the erodible aggregates less than 0.42 mm. treated samples also showed a good stability against breakdown under repeated sieving and the effect of cyclic freezing and thawing on the mean weight diameter factor MWD. The results of repeated sieving test RST showed that petroleum mixtures create a stable crust preventing the bare sand dunes from erosion.

Elaboración y caracterización de harina de oca proveniente de tres variedades, (zapallo, pauccar y mestiza), para uso en productos cárnicos

Se elaboró la harina de oca proveniente de tres variedades (Mestiza (V1), Pauccar, (V2) y Zapallo (V3)) para su uso en productos cárnicos de pasta fina, se evaluó las características físicas, químicas, microbiológicas, funcionales y sensoriales. Se analizó las características físicas aplicando las normas NTE INEN 0154 para tamices de ensayo y NTE INEN 0517 determinación de tamaño de partículas, para los químicos se usó el método de la Asociación de Químicos Analíticos Oficiales, para los análisis microbiológicos se empleó la norma NTE INEN 616 requisitos para harina de trigo, en los funcionales se aplicó la técnica de Anderson, para los análisis sensoriales se manejó un modelo descriptivo. La investigación se distribuyó bajo un diseño completamente al alzar, con 5 repeticiones y una unidad experimental de 500 gramos, empleando la prueba de tukey (P≤0,05). La composición nutricional determinó valores promedios de las tres variedades como: Humedad: 8,60 %; Grasa: 1,73 %; Fibra: 6,76 %; Proteína: 6,32 %; Cenizas: 5,18 %; Carbohidratos: 71,42 %. Se obtuvo un rendimiento promedio de 28 % para las tres variedades y en la granulometría la Variedad Mestiza obtuvo el 89,08 % que atravesó el tamiz con diámetro de 250 micras. Los análisis microbiológicos indicaron que los mohos, levaduras y coliformes presentaron niveles muy bajos que cumplen con los requerimientos establecidos en la norma INEN 616 (2015).Los parámetros estudiados en las propiedades funcionales presentaron diferencias significativas alcanzando valores como: Absorción: 3,54 mL/g; Capacidad de Retención: 7,81 mL/g; Solubilidad: 4,06 % y Poder de Hinchamiento: 3,59 g. Se demostró que la Variedad Mestiza (V1) fue la más aceptada, presentando los mejores atributos sensoriales con un 100 % de aceptabilidad. Se concluye que las harinas de oca de las tres variedades pueden utilizarse en la preparación de productos cárnicos de pasta fina (mortadelas, salchicha vienesa, salchicha Frankfurt).

Modified Marshall Test assessment for emulsified asphalt cold mixes

Asphalt cold mixes are attractive to transportation agencies for their simplicity in set-up, less energy requirement, ease of application, and environmentally friendliness, though it suffers setbacks in terms of lack of a universally acceptable mix campaign, high water susceptibility, and low mechanical strength at initial stages of construction. However, they are widely used for rehabilitation and maintenance works, and to a lesser extent construction in low-trafficked roads. Notable among the cold mixtures is polymer modified emulsified asphalt micro-surfacing, which is used as a thin non-structural layer for the restoration of skid resistance and waterproofing. Marshall test is used to assess its performance similar to a structural wearing course layer. This study assessed the mechanical performance of cold mixtures by a modified Marshall mix employing a low viscosity cationic quick set emulsion (CQS-1h) and a cationic rapid set emulsion (RS-1k) and a 60/70 penetration grade binder. Rheological criteria assessment was conducted on both emulsions including particle charge, residue by evaporation, settlement and storage stability, solubility in inorganic solvent sieve test, and Saybolt Furol viscosity, while the residue from evaporation was tested for microstructural and mechanical performance, 65% and 63% residue by evaporation, dissolved in trichloroethylene at 95% and 100% for CQS-1h and RS-1k respectively.

Geometrical and geotechnical characterization of the earth fissures appeared in the Guadalentín Valley (southeastern Spain) after the September 2012 flooding

Abstract. Two earth fissures appeared in Murcia province (southeastern Spain) after the flood occurred because of a heavy downpour on 28 September 2012. In this area, located within the Guadalentín Valley, up to 212 L m−2 was reported that day. More than 200 agricultural exploitations were destroyed by the flooding, with a devastating effect on many infrastructures, such as a main A-7 highway bridge that collapsed in this event. The earth fissures appeared after this flooding in the towns of Puerto Lumbreras and Totana. The first fissure showed a straight-line direction approximately parallel to the main geological structures of the Guadalentín Valley. The total length of the fissure was 400 m and was 2 to 3 m in depth. The soil in the fissure is classified as a low-plasticity silt with some sand and clay, ML, according to the Unified Soil Classification System. From the sieve and hydrometer tests, the percentage of silt in these samples was between 48 % and 68 %, the clay content between 12 % and 30 % and the sand content between 2 % and 40 %. The plasticity index was smaller than 9.2 for all the samples. To evaluate the piping and internal erosion susceptibility of the soil, pinhole, crumb and geochemical tests were done on the collected samples. A result of non-dispersive soil was obtained from crumb and pinhole tests. Nevertheless, the pH, sodium adsorption ratio and exchangeable sodium percentage tests showed that some samples could be affected by the dispersion of the soil. Also, the collapsible potential of the soil was studied, showing negative results for all the samples except for that collected at the southern end of the fissure, which showed a medium to high potential. Concerning the Totana fissure, it appeared with different branches and holes instead of as a rectilinear pattern. The total length of the fissure was 190 m, with the soil characterized as a silty soil. Lastly, INSAR data, GPS, GPR and land subsidence maps were used to study the possible origin of these fissures.

Rheological criteria assessment of a rapid setting emulsion as compared to quick set for emulsified asphalt cold mixes

Pavement deterioration is inevitable on roads. Unlike structural failures that can only be remedied by total reconstruction, road’s functional failures are corrected through effective maintenance works. Preventive maintenance in the form of an emulsified asphalt cold slurry micro-surfacing is considered superior to corrective maintenance – which is a reactive approach. Exploring alternative(s) to the normal quick setting emulsion used for pavement preservation maintenance will make it more robust and cost-effective. This study conducted an assessment of the key parameters specified by the department of public works (Jabatan Kerja Raya) JKR-2008 and International Slurry Surfacing Association (ISSA A143) specifications for emulsified asphalts emulsions used for cold mixes, specifically, emulsified asphalt micro-surfacing mixtures used for pavement maintenance. Cationic quick set (CQS-1h) and Rapid Set (RS-1k) emulsions were tested in the Transportation laboratory of UTM under controlled laboratory conditions. Tests include settlement and storage stability, particle charge, residue by evaporation, sieve test, and Say bolt Furol viscosity, while the residue from evaporation was tested for microstructural and mechanical performance, results were compared with JKR-2008 and ISSA A143 standard specifications. The result indicated that although the desirability for opening traffic within 1hr is not guaranteed with RS-1k, yet, it gives promising similar properties with CQS whilst satisfying cold mix requirement.

Effect of wet-dry cycles on disintegration characteristics of clay-bearing sandstone with UF cracks

UF cracks in rock masses commonly occur due to the unloading effect, which constantly happens after the variation of in-situ stress field or rock excavation. When undergoing periodic water fluctuation, rock mass with UF cracks is vulnerable to deterioration or even disintegration, especially for clay-bearing sandstone. To study the effect of changes in moisture on rock samples with UF cracks, clay-bearing sandstone from the Triassic Badong group in the Three Gorges Reservoir Area were chosen and investigated. The rock samples with UF cracks are obtained by conducting triaxial unloading confining pressure experiment. The effect of wet-dry cycles on the morphology properties and microstructure of the UF surface was investigated. The characteristics of particle-size uniformity from the sieve test were obtained by the calculation of RMS of particle contents. The test results show that UF cracks widen significantly and the disintegrated mass increases rapidly in the first three wet-dry cycles, while the fractal dimension of UF surface decreases sharply, but afterwards the disintegrated mass changes gently and the UF surface tends to be flat and smooth. Then, the RMS calculation of particle contents quantitatively evaluate the clay-bearing sandstone’s disintegration properties, which indicate the particle uniformity plays a key role on its disintegration mechanism. During wet-dry cycles, the tested samples tend to disintegrate more rapidly and entirely with the decrease of particle uniformity.

Direct Synthesis of 5A Zeolite From Palygorskite: The Influence of Crystallization Directing Agent on the Separation Performance for Hexane Isomers

AbstractThe efficient separation of hexane isomers from the light naphtha fraction is a significant challenge in the petrochemical industry. 5A zeolite adsorbent is used commercially to sieve alkane isomers. In this study, 5A zeolites were synthesized using a low-cost natural clay mineral precursor, i.e. palygorskite (PAL), with the addition of crystallization directing agent (CDA). By varying the mass ratio of CDA/deionized water, 5A zeolites were obtained as CDA-5%, CDA-7.5%, and CDA-10%. All products were submicron particles with an average particle size of 400–800 nm. A sieving test of CDA-induced 5A zeolites was carried out on hexane adsorbates including n-hexane (nHEX), 2-methylpentane (2MP), and 3-methylpentane (3MP). According to vapor-phase batch adsorption experiments, a significant equilibrium amount (0.149 g/g) of nHEX and only 0.0321 g/g 2MP and 0.0416 g/g 3MP were adsorbed on the 5A zeolite product with CDA-5%. The dynamic adsorption performance of 5A zeolite (CDA-5%) was evaluated by breakthrough curves of binary mixtures of nHEX/2MP and nHEX/3MP. Palygorskite 5A (PAL 5A) zeolite achieved maximum dynamic adsorption capacities of nHEX (0.16 g/g in both cases) at 200°C and 1.2 MPa total pressure. This work provided an economic alternative for the synthesis of 5A zeolites using natural clay minerals instead of chemical raw materials.

Vapor phase assembly of urea–amine compounds and their protection against the atmospheric corrosion of carbon steel

Two kinds of polyamine compounds, bis-cyclohexylaminoethylurea (BCAU) and monocyclohexylaminoethylurea (MCAU), are synthesized via Mannich reaction. The anticorrosion films on carbon steel surface are prepared by the vapor phase assembly method. After 72 h volatilization at 50°C, the mass-loss for BCAU and MCAU in the closed space are 1.13% and 1.45%. The volatile-inhibiting sieve (VIS) test, the volatile-inhibiting ability test and the electrochemical impedance spectroscopy measurement are used to compare the prevention of the atmospheric corrosion by the assembly film. BCAU and MCAU have 92.44% and 87.56% inhibition efficiency for carbon steel in VIS test. On the basis of theoretical calculation and surface analysis, the protective film structures on carbon surface from the vapor phase assembly are proposed.

Prediction of Pore Size Characteristics of Needle‐Punched Nonwoven Geotextiles Subjected to Uniaxial Tensile Strains

A modified theoretical model has been proposed to predict the pore size characteristics of nonwoven geotextiles under certain uniaxial tensile strains, considering the difference between the out‐of‐plane Poisson’s ratio and the in‐plane Poisson’s ratio of geotextiles. The pore size distributions (PSDs) and O95 subjected to different levels of uniaxial tensile strains in two needle‐punched nonwoven geotextiles have been investigated by the dry sieving test. The variation of the fibre orientation with tensile strains and the corresponding effect on pore sizes has been evaluated by image analysis. The out‐of‐plane Poisson’s ratio and the in‐plane Poisson’s ratio of geotextiles have been examined. A comparison has been made between the predictions of the original and the modified models. It is shown that the modified model can more accurately predict the decreasing rate of the PSDs, O95, and O98 than the original one. The corrected theoretical O95 and O98 under certain strains can provide a reference for the filtration design under engineering strains. The fibres reorientating to the loading direction result in the increase of the directional parameter with increasing tensile strains, which leads to the decrease of pore sizes. The theoretical PSDs are sensitive to the variation of directional parameter.

Quality evaluation of microwaved and non-microwaved <em>chakki atta</em> flour under storage

Chakki atta is ground wheat which is a neutral form available without any addition or subtraction and thus, it is mostly used in rural areas. This research was conducted to evaluate the quality changes of chakki atta flour during the storage and to study the effect of microwave on the quality of chakki atta flour. Chakki atta flour was packed in polyethylene bags separately and subjected to microwave (700 W for 60 s) and the quality changes were assessed within 12 weeks at storage temperature 27°C. The quality characteristics such as smell test, sieve test, long moisture (hot air oven method), moisture using NIR (Near Infrared Ray), protein using NIR, ash using NIR, wetgluten, fat acidity, colour and weevil count were evaluated at two weeks interval. Crude fat and crude fibre content were evaluated at four weeks interval. Chapatti was prepared from microwaved and non-microwaved flour and the sensory characteristics were evaluated at four weeks interval. Physio-chemical properties of chakki atta such as colour, protein, crude fat and fat acidity changed with the storage period and microwaving treatment prominently influenced on moisture, wet gluten, colour, protein, ash, and fat acidity. There was no any weevil infestation found in both flour. Sensory characteristics of the chapatti were not affected by storage in both microwaved and non-microwaved flour. It can be concluded that chakki atta flour can be stored at 27°C for three months from the date of manufactured.

Utilization of Palm Fruit Fibers as Constituent Materials for Hand Mould Clay Bricks

The production process of palm oil generates a huge amount of waste. As Nigeria is one of the largest producing countries, the fruit fiber wastes from palm oil processing have received a low level of waste management and have been a long-term environmental concern. This study is focused on recovery of the palm fruit fibers and its utilization as a constituent material for locally hand mold clay bricks. Varying percentages (1% to 3%) of palm fruit fiber was introduced into local hand mold clay. The bricks produced were tested for optimum moisture content and dry density. Some preliminary tests such as natural moisture content determination (wet and dry), Specific gravity test, Particle size distribution test (Sieve analysis), Atterberg limit test, Compaction test (Standard Proctor), Water absorption test, and Compressive strength test was carried out. The results show a decrease in optimum moisture content as the percentage of the palm fruit fibers increased from 1% to 3% in the soil sample while the maximum dry density increased. With the addition of 1% to 3% of the palm fruit fibers and the mix sun-dried, noticeable improvement in the compaction characteristics of the soil sample was observed. It can be deduced from the results that for a good construction clay soil, the lower the moisture content, the higher the dry density and the better the quality of bricks. Production of clay bricks with palm fruit fibers could serve as an economic substitute for the growing cost of sandcrete blocks.

From glass dump to phytoremediation park

The Landfill mining was introduced in research in Sweden for more than three and a half decades ago. During recent years, the focus has been on the glass dumps in the Kingdom of Crystal in southeastern Sweden. Mapping of the dumps, test pit excavations, sieving and sorting of the glass masses, characterization, laboratory extraction of the metals in the glass was performed as well as measurements of radioactivity done. The polluted soil underneath the removed glass masses was treated by remediation. At one of places at the Kingdom of Crystal a phytoremediation/tourist park was established in Orrefors including a summer glasswork for tourist activities.

Study on Spatial Variation of Shear Mechanical Properties of Soil-rock Mixture

The soil-rock mixture (SRM) is a kind of special engineering geological material, which has been exposed to the field for a long time and is affected by rainwater seepage, geological force, slope sliding force and human activities, resulting in the spatial variability of its mechanical properties. Taking the SRM distributed on a slope of the Three Gorges Reservoir area as the research object, four test locations were selected along and transverse the slope. First, in-situ large-scale direct shear test was carried out, and then the laboratory large-scale direct shear test, particle sieving test, and water content test were carried out in the undisturbed sample to study the variation of shear mechanical properties of SRM distributed in different spatial locations. The results show that: (1) Under the same normal stress, the peak strength of the SRM decreases at a similar rate along the slope direction and the transverse slope direction. (2) The cohesion of the SRM is continuously strengthened, and the friction angle is continuously deteriorated along the slope from high to low, the cohesion and friction angle are almost no variability along the transverse slope. (3) The mechanism of the above-mentioned variation in the shear mechanics parameters of SRM is that the lower the elevation along the slope, the more fragmented the rock, the lower the rock content. (4) Spatial variability models of cohesion and friction angle of SRM were established, which can provide references for related engineering applications.

Establishment of virtual vibrating sieve based on PFC3D

The generation of virtual aggregate, close to realistic aggregate by numerical tool, is a key step in investigating the mechanical properties of asphalt mixture from the mesoscopic level. To verify the accuracy of assemblage of aggregate, this paper is based on the improved algorithm of random cutting technology previously proposed, using PFC3D editing program to establish a vibrating sieve, and the reliability of the improved algorithm was verified by sieving test. The results show that the improved algorithm of the irregular polyhedron random cutting technique proposed by the author can ensure that the gradation of the aggregate is consistent with the actual, and the sieving test can be used to evaluate the quality of the virtual aggregate based on PFC3D.