Study on slope stability due to the influence of excavation of the high-speed rail tunnel

In this study, based on a high-speed railway tunnel project undercrossing slope, model tests and numerical simulation methods were carried out to study the interaction law of tunnel excavation and slope stability. Firstly, the numerical model of finite element analysis and the numerical model of excavation tunnel under the slope were established. The influence mechanism of tunnel excavation on the stability of the slope was studied. Then the physical simulation for the typical working conditions was carried out in the model test. The test results showed that the tunnel excavation is prone to cause disturbance to the displacement field of the slope. The monitoring data of the slope displacement caused by the tunnel excavation were in good agreement with the numerical analysis. The influence area of tunnel excavation on the deformation of the slope range from 1.5 times the tunnel span, which should be well strengthened and monitored. The conclusion can provide reference for the overall stability of tunnels and slopes in mountain tunnel construction

Unlocking the role of pores in chloride permeability of recycled concrete: A multiscale and a statistical investigation

Chloride ingress is strongly associated with the properties of pores in recycled concrete. To unlock its role in chloride permeability, the pore structures of concrete containing various quantities of recycled coarse (fine) aggregates were analyzed from multi-scales, and the outcomes were further verified by the statistical investigation. The results show that different roles that recycled coarse (fine) played in terms of the pore structures of recycled concrete, as reflected by their volume and diameter of mesopores and micropores, respectively. Meanwhile, Unlike the previous studies, two key pore parameters (i.e., PV < 1 and PT) were put forward, revealing their strong interconnections with chloride diffusion of recycled concrete, as confirmed by the statistical analysis. Further, a model concerning chloride permeability of recycled concrete was proposed on a basis of the probability theory, and the newly proposed factor Rp (relied on the previous two pore parameters) has a great relevance to effective chloride diffusion. Therefore, this work enhances accuracy of prediction for chloride diffusivity and durability associated with recycled concrete

Effects of imidazolium-based ionic liquids on the isobaric vapor-liquid equilibria of methanol plus dimethyl carbonate azeotropic systems

The separation of methanol (MeOH) and dimethyl carbonate (DMC) is important but difficult due to the formation of an azeotropic mixture. In this work, isobaric vapor-liquid equilibrium (VLE) data for the ternary systems containing different imidazolium-based ionic liquids (ILs), i.e. MeOH + DMC + 1-butyl-3-methy-limidazolium bis[(trifluoromethyl)sulfonyl]imide ([Bmim][Tf2N]), MeOH + DMC + 1- ethyl-3-methyl-imidazolium bis [( trifluoromethyl)sulfonyl]imide ([Emim][Tf2N]), and MeOH + DMC + 1-ethyl-3-methylimidazolium hexafluorophosphate ([Emim][PF6])) were measured at 101.3 kPa. The mole fraction of IL was varied from 0.05 to 0.20. The experimental data were correlated with the NRTL and Wilson equations, respectively. The results show that imidazolium-based ILs were beneficial to improve the relative volatility of MeOH to DMC, and [Bmim][Tf2N] showed a much more excellent performance on the activity coefficient of MeOH. The interaction energies of system componentswere calculated using Gaussian program, and the effects of cation and anion on the separation coefficient of the azeotropic system were discussed. (C) 2019 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved

Ionic liquids tailored and confined by one-step assembly with mesoporous silica for boosting the catalytic conversion of CO2 into cyclic carbonates

On the basis of economic and energy-saving criteria, the minimum effective dose of ionic liquids (ILs) for the catalytic conversion of CO2 into cyclic carbonates was first explored by confinement. With one-step assembly of mesoporous silica (mSiO(2)) by using a fixed amount of silicon source with varying amounts of ILs as templates, certain amounts of 1-ethyl-3-methyl imidazolium bromides (EmimBr) were tailored and confined in mSiO(2). The confined ILs (EmimBr@mSiO(2)) retained the advantages of homo- and heterogeneous catalysts, exhibiting higher performance than bulk EmimBr under identical reaction conditions. Amongst all the prepared materials, EmimBr@mSiO(2) with the lowest amount of EmimBr (6.9 wt%) exhibited the biggest improvement in catalytic activity, achieving a TOF of 112.6 h(-1) which is almost 1.7 times the bulk phase with good recyclability. The boosted catalytic activity could be attributed to the larger proportion of mesopores, the better dispersity of EmimBr (Si/Br = 25) and the synergistic effect from more exposed silanol groups (Si-OH/Br = 8) in the structure. The good recyclability was then explained by the XPS analysis and density functional theory (DFT) calculation, which confirmed that the compressing effect from Si-OH could enhance the cation and anion interaction to stabilize ILs in the space more firmly when less ILs were confined

Effects of imidazolium-based ionic liquids on the isobaric vapor–liquid equilibria of methanol+dimethyl carbonate azeotropic systems

The separation of methanol(MeOH)and dimethyl carbonate(DMC)is important but difficult due to the formation of an azeotropic mixture.In this work,isobaric vapor–liquid equilibrium(VLE)data for the ternary systems containing different imidazolium–based ionic liquids(ILs),i.e.MeOH+DMC+1-butyl-3-methy-limidazolium bis(trifluoromethyl)sulfonylimide(BmimTf2N),MeOH+DMC+1-ethyl-3-methyl-imidazolium bis(trifluoromethyl)sulfonylimide(EmimTf2N),and MeOH+DMC+1-ethyl-3-methylimidazolium hexafluorophosphate(EmimPF6)were measured at 101.3 kPa.The mole fraction of IL was varied from0.05 to 0.20.The experimental data were correlated with the NRTL and Wilson equations,respectively.The results show that imidazolium-based ILs were beneficial to improve the relative volatility of MeOH to DMC,andBmimTf2 Nshowed a much more excellent performance on the activity coefficient of MeOH.The interaction energies of system components were calculated using Gaussian program,and the effects of cation and anion on the separation coefficient of the azeotropic system were discussed

Effects of imidazolium-based ionic liquids on the isobaric vapor–liquid equilibria of methanol+dimethyl carbonate azeotropic systems

The separation of methanol(MeOH)and dimethyl carbonate(DMC)is important but difficult due to the formation of an azeotropic mixture.In this work,isobaric vapor–liquid equilibrium(VLE)data for the ternary systems containing different imidazolium–based ionic liquids(ILs),i.e.MeOH+DMC+1-butyl-3-methy-limidazolium bis(trifluoromethyl)sulfonylimide(BmimTf2N),MeOH+DMC+1-ethyl-3-methyl-imidazolium bis(trifluoromethyl)sulfonylimide(EmimTf2N),and MeOH+DMC+1-ethyl-3-methylimidazolium hexafluorophosphate(EmimPF6)were measured at 101.3 kPa.The mole fraction of IL was varied from0.05 to 0.20.The experimental data were correlated with the NRTL and Wilson equations,respectively.The results show that imidazolium-based ILs were beneficial to improve the relative volatility of MeOH to DMC,andBmimTf2 Nshowed a much more excellent performance on the activity coefficient of MeOH.The interaction energies of system components were calculated using Gaussian program,and the effects of cation and anion on the separation coefficient of the azeotropic system were discussed

Experimental, Modeling and Process Simulation Studies of Ethylene Oxide Absorption

Water as an absorbent for ethylene oxide has been extensively investigated over the past decades, but many issues about this system still remain such as solvent loss, high energy consumption. In this work, a new absorbent ethylene carbonate (EC) was applied and the solubility behaviors of carbon dioxide, ethylene, methane in the ethylene carbonate (EC) were investigated with using static apparatus at temperatures of 313.2, 323.2, and 333.2 K. And the vapor liquid equilibrium(VLE) of ethylene oxide(EO) and EC have been studied with gas chromatography analysis method at temperatures of 333.2, 343.2, and 353.2 K. The NRTL and Wilson models were used to correlate experimental solubility data and VLE data. The conceptual H2O-based and EC-based EO absorption process for EO-containing mixed gas purification was established and optimized with using the regressed NRTL model parameters. The results showed that the purification process of EC used as absorbent could reduce energy consumption 37.6 Gcal/h. (C) 2020 Elsevier B.V. All rights reserved