The viscosity-time curve of a single-component polyurethane(PU)was examined to determine the mixing and compacting temperatures of its mixture and investigate the curing and mechanical properties of single-component P...The viscosity-time curve of a single-component polyurethane(PU)was examined to determine the mixing and compacting temperatures of its mixture and investigate the curing and mechanical properties of single-component PU porous elastic mixture(PPEM).The curing properties of the single-component PU and PPEM were studied with Fourier transform infrared spectroscopy(FTIR)and Marshall test.The mechanical properties of PPEM were explored via the following tests:rutting test,3-point bending test,soaked Marshall stability test,freeze-thaw splitting test,and Cantabro test.The effects of a water bath on the stability of aggregate-PU/asphalt mortar-aggregate systems were evaluated through a pull-out test and a shear test.The results show that the recommended mixing temperatures of toluene diisocyanate and methylene diphenyl diisocyanate range from 75 to 80℃and from 64 to 68℃,respectively.Room temperature(25℃)can be adopted as the compacting temperature of PPEM.PPEM can be fully cured in 4 d.Nevertheless,the water sprinkle method can obviously shorten the full curing time of PPEM.PPEM exhibites good resistance to rutting,brittle cracking,and raveling.The adhesive and shear strength of aggregate-PU/asphalt mortar-aggregate systems are negatively related to water bath duration.展开更多
Mechanical behaviors of granular materials are complicated and greatly influenced by the particle shape.Current,some composite approaches have been proposed for realistic particle shape modelling within discrete eleme...Mechanical behaviors of granular materials are complicated and greatly influenced by the particle shape.Current,some composite approaches have been proposed for realistic particle shape modelling within discrete element method(DEM),while they cannot give a good representation to the shape and mass properties of a real particle.In this work,a novel algorithm is developed to model an arbitrary particle using a cluster of non-overlapping disks.The algorithm mainly consists of two components:boundary filling and domain filling.In the boundary filling,some disks are placed along the boundary for a precise representation of the particle shape,and some more disks are placed in the domain to give an approximation to the mass properties of the particle in the domain filling.Besides,a simple method is proposed to correct the mass properties of a cluster after domain filling and reduce the number of the disks in a cluster for lower computational load.Moreover,it is another great merit of the algorithm that a cluster generated by the algorithm can be used to simulate the particle breakage because of no overlaps between the disks in a cluster.Finally,several examples are used to show the robust performance of the algorithm.A current FORTRAN version of the algorithm is available by contacting the author.展开更多
By the generalized Kelvin creep model,rheological characteristics of deep softrock and long-term mechanical behaviors of support structures were simulated.Mechanicaldeformation characteristics of support structures un...By the generalized Kelvin creep model,rheological characteristics of deep softrock and long-term mechanical behaviors of support structures were simulated.Mechanicaldeformation characteristics of support structures under different lining circumstanceswere also analyzed on the basis of deducing the relationship between the generalizedKelvin creep model and implicit creep equations in ANSYS FEM software.The resultsshow that high stress of deep tunnels is the main factor in creep damage;the surroundingrock's deformation binding effect due to lining increases as the thickness increases but theeffect becomes very weak when it increases to a certain value;contact pressure on thelining decreases as its thickness decreases.展开更多
基金The Fundamental Research Funds for the Central Research Institute (No. 2020-9054)。
文摘The viscosity-time curve of a single-component polyurethane(PU)was examined to determine the mixing and compacting temperatures of its mixture and investigate the curing and mechanical properties of single-component PU porous elastic mixture(PPEM).The curing properties of the single-component PU and PPEM were studied with Fourier transform infrared spectroscopy(FTIR)and Marshall test.The mechanical properties of PPEM were explored via the following tests:rutting test,3-point bending test,soaked Marshall stability test,freeze-thaw splitting test,and Cantabro test.The effects of a water bath on the stability of aggregate-PU/asphalt mortar-aggregate systems were evaluated through a pull-out test and a shear test.The results show that the recommended mixing temperatures of toluene diisocyanate and methylene diphenyl diisocyanate range from 75 to 80℃and from 64 to 68℃,respectively.Room temperature(25℃)can be adopted as the compacting temperature of PPEM.PPEM can be fully cured in 4 d.Nevertheless,the water sprinkle method can obviously shorten the full curing time of PPEM.PPEM exhibites good resistance to rutting,brittle cracking,and raveling.The adhesive and shear strength of aggregate-PU/asphalt mortar-aggregate systems are negatively related to water bath duration.
基金Project(2011CB013504)supported by the National Basic Research Program(973 Program)of ChinaProject(2013BAB06B01)supported by Key Projects in the National Science&Technology Pillar Program during the Twelfth Five-year Plan Period,China+1 种基金Projects(51309089,51479049)supported by National Natural Science Foundation of ChinaProject(487237)supported by Natural Sciences and Engineering Research Council of Canada
文摘Mechanical behaviors of granular materials are complicated and greatly influenced by the particle shape.Current,some composite approaches have been proposed for realistic particle shape modelling within discrete element method(DEM),while they cannot give a good representation to the shape and mass properties of a real particle.In this work,a novel algorithm is developed to model an arbitrary particle using a cluster of non-overlapping disks.The algorithm mainly consists of two components:boundary filling and domain filling.In the boundary filling,some disks are placed along the boundary for a precise representation of the particle shape,and some more disks are placed in the domain to give an approximation to the mass properties of the particle in the domain filling.Besides,a simple method is proposed to correct the mass properties of a cluster after domain filling and reduce the number of the disks in a cluster for lower computational load.Moreover,it is another great merit of the algorithm that a cluster generated by the algorithm can be used to simulate the particle breakage because of no overlaps between the disks in a cluster.Finally,several examples are used to show the robust performance of the algorithm.A current FORTRAN version of the algorithm is available by contacting the author.
基金Supported by Open Foundation Project of Education Ministry Key Laboratory about Mine Disaster Prevention and Control(MDPC0811)Research Project"Spring Bud Plan"of Shandong University of Science and TechnologyShandong University of Science and Technology Innovation Fund Grant(yca2008-04-01)
文摘By the generalized Kelvin creep model,rheological characteristics of deep softrock and long-term mechanical behaviors of support structures were simulated.Mechanicaldeformation characteristics of support structures under different lining circumstanceswere also analyzed on the basis of deducing the relationship between the generalizedKelvin creep model and implicit creep equations in ANSYS FEM software.The resultsshow that high stress of deep tunnels is the main factor in creep damage;the surroundingrock's deformation binding effect due to lining increases as the thickness increases but theeffect becomes very weak when it increases to a certain value;contact pressure on thelining decreases as its thickness decreases.
