ORCID Profile
0000-0003-4886-1398
Current Organisation
Zhengzhou University
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Publisher: Hindawi Limited
Date: 21-09-2022
DOI: 10.1155/2022/4923385
Abstract: At present, polyurethane (PU) has been extensively used as a grouting material in civil engineering. The mechanical properties of PU are the key to achieving the desirable grouting effect. This study presents the research results of the mechanical behavior of PU matrix under tensile, successive cyclic tensile, and stress relaxation at the nanoscale, using the coarse-grained molecular dynamics simulation method. The influences of the number of molecule chains and strain rate on the tensile mechanical properties are discussed, and the tensile deformation mechanism of PU matrix is revealed. The tensile strength of PU matrix is independent of loading path, and after yielding, the strain of PU matrix contains the elastic strain, plastic strain, and viscous strain. In the stress relaxation process, the evolution of the axial stress is mainly caused by the varied van der Waals interactions. The stress relaxation behavior of PU matrix can be described by the viscoelastic model consisting of one elastic element in parallel with one Maxwell element.
Publisher: Elsevier BV
Date: 08-2017
Publisher: MDPI AG
Date: 16-03-2023
Abstract: In this study, the uniaxial compression and cyclic loading and unloading experiments were conducted on the non-water reactive foaming polyurethane (NRFP) grouting material with a density of 0.29 g/cm3, and the microstructure was characterized using scanning electron microscope (SEM) method. Based on the uniaxial compression and SEM characterization results and the elastic-brittle-plastic assumption, a compression softening bond (CSB) model describing the mechanical behavior of micro-foam walls under compression was proposed, and it was assigned to the particle units in a particle flow code (PFC) model simulating the NRFP s le. Results show that the NRFP grouting materials are porous mediums consisting of numerous micro-foams, and with the increasing density, the diameter of the micro-foams increases and the micro-foam walls become thicker. Under compression, the micro-foam walls crack, and the cracks are mainly perpendicular to the loading direction. The compressive stress–strain curve of the NRFP s le contains the linear increasing stage, yielding stage, yield plateau stage, and strain hardening stage, and the compressive strength and elastic modulus are 5.72 MPa and 83.2 MPa, respectively. Under the cyclic loading and unloading, when the number of cycles increases, the residual strain increases, and there is little difference between the modulus during the loading and unloading processes. The stress–strain curves of the PFC model under uniaxial compression and cyclic loading and unloading are consistent with the experimental ones, well indicating the feasibility of using the CSB model and PFC simulation method to study the mechanical properties of NRFP grouting materials. The failure of the contact elements in the simulation model causes the yielding of the s le. The yield deformation propagates almost perpendicular to the loading direction and is distributed in the material layer by layer, which ultimately results in the bulging deformation of the s le. This paper provides a new insight into the application of the discrete element numerical method in NRFP grouting materials.
Publisher: Walter de Gruyter GmbH
Date: 2020
Abstract: Carbon nanomaterials, predominantly carbon nanofibers, carbon nanotubes, graphene, graphene nanoplates, graphene oxide and reduced graphene oxide, possess superior chemical, physical and mechanical properties. They have been successfully introduced into ordinary Portland cement to give enhancements in terms of mechanical properties, durability and electrical/thermal conductivity, and to modify the functional properties, converting conventional cement-based materials into stronger, smarter and more durable composites. This paper provides a comprehensive review of the properties of carbon nanomaterials, current developments and novel techniques in carbon nanomaterials enhanced cement-based composites (CN-CBCs). Further study of the applications of CN-CBCs at industrial scale is also discussed.
Publisher: Walter de Gruyter GmbH
Date: 2022
Abstract: Graphene oxide (GO) has been widely used to enhance the tensile/compressive strength of cement-based materials, whereas its shear reinforcing effect is still unknown. To verify the feasibility of GO as a shear reinforcement material, the shear reinforcing effect of GO on cement was experimentally investigated. The nanoscale Young’s modulus ( E ) of the GO-enhanced cement was measured with the peak force quantitative nanomechanical mapping method to clarify the enhancing mechanism. Results show that the addition of 0.02 and 0.04 wt% GO in cement could improve the shear strength by about 12 and 40%, respectively, which is mainly due to the enhanced cohesion, and at the nanoscale, the average E of the low-density hydration product increased by 1.6 and 13.2%, whereas that of high-density hydration product remains almost unchanged. There exist fewer nanoholes/cracks and unhydrated cement grains but more the high-density hydration product in GO-enhanced cement, implying a denser microstructure and higher hydration degree. GO can enhance the shear strength of cement because of its enhancing effects on the microstructure, nanoscale Young’s modulus of hydration products, as well as the hydration degree.
Publisher: Elsevier BV
Date: 05-2017
Publisher: Walter de Gruyter GmbH
Date: 2022
Abstract: Two-component foaming polymer (TFPU) grouting material is increasingly used in civil engineering. Its compressive strength is key to achieving the desired enhancing effect. The constitutive model of TFPU grouting material is a theoretical basis to evaluate the strength performance, which, however, is not fully understood. Here the uniaxial compression experiment of TFPU s les of different densities (0.11–0.53 g·cm −3 ) was conducted. Based on the stress–strain curves, the damage evolution equation of each s le was obtained by function fitting, followed by the establishment of statistical damage constitutive model. The model was simplified to a universal function with density as the argument. Results show that the stress–strain curves contain the initial compression stage, linear elastic stage, yield stage, yield plateau stage, and strain hardening stage regardless of the varied density. The variation laws of the damage with strain conform to the form of first-order decay exponential function. The theoretical stress–strain curves are in good agreement with the experimental ones, indicating that the statistical damage constitutive model can well reflect the mechanical behavior of TFPU grouting material. With this constitutive model, the mechanical properties of TFPU grouting material can be obtained according to the density alone, which is more convenient for practical engineering applications.
Publisher: Elsevier BV
Date: 07-2020
Publisher: SPIE
Date: 22-12-2022
DOI: 10.1117/12.2657847
Publisher: Elsevier BV
Date: 10-2022
Publisher: Elsevier BV
Date: 05-2023
Publisher: Elsevier BV
Date: 02-2022
Publisher: Elsevier BV
Date: 05-2019
Publisher: Elsevier BV
Date: 10-2023
Publisher: Elsevier BV
Date: 10-2020
Publisher: Hindawi Limited
Date: 21-04-2022
DOI: 10.1155/2022/1843131
Abstract: The newly developed two-component polymer (TFPU) cut-off walls have great application potential in civil engineering for water-seepage prevention. Investigating the mechanical interactions between TFPU and soil from the theoretical perspective can provide a basis for furtherly evaluating the stability of TFPU cut-off walls, which, however, has not been conducted. In this study, based on the shear testing results, the shear damage model of the TFPU-bentonite contact surface was established. Studies show that the TFPU-bentonite contact surface performs strain-softening behavior under shear and that the strain-softening behavior becomes less and less obvious when the normal stress increases. The theoretical shear stress-strain curves are in good consistent with the experimental ones, and the maximum differences between the theoretical shear stress and shear strain at yield and the experimental ones are about 3.88% and 3.40%, respectively, indicating that the shear damage model can reflect the mechanical properties of the TFPU-bentonite contact surface. The critical damage of the contact surface increases from 0.05 to 0.50 in the power function way when normal stress increases from 75 to 1200 kPa, implying that the shear failure of the contact surfaces changes from brittleness to ductility. This study provides a theoretical base for evaluating the influences of the TFPU-soil contact surface on the stability of the TFPU cut-off wall structures.
Publisher: MDPI AG
Date: 20-10-2201
DOI: 10.3390/NANO8100858
Abstract: Multi-walled carbon nanotubes (MWCNTs) are promising nanoreinforcing materials for cement-based composites due to their superior material properties. Dispersion of MWCNTs is key for achieving the most effective way of enhancing efficiency, which is challenging in an alkaline cementitious environment. In this study, humic acid (HA) was used to stabilize the degree of dispersion of MWCNTs in an alkaline environment. The efficiency of HA in stabilizing MWCNT dispersion in cement composites was characterized using an ultraviolet spectrophotometer. The influences of HA on the workability and mechanical properties of ordinary Portland cement (OPC) reinforced with MWCNTs were evaluated, and the results revealed that the addition of HA can improve the stability of MWCNT dispersion in an alkaline environment. A concentration of 0.12 wt.% HA/S added to MWCNT suspensions was found to perform the best for improving the dispersion of MWCNTs. The addition of HA results in a decreased workability of the OPC pastes but has little influence on the strength performance. HA can affect the mechanical properties of OPC reinforced with MWCNTs by influencing the dispersion degree of the MWCNTs. An optimum range of HA (0.05–0.10 wt.%) is required to achieve the optimum reinforcing efficiency of MWCNTs.
Publisher: MDPI AG
Date: 27-05-2022
DOI: 10.3390/EN15113978
Abstract: The increasing use of high-voltage transmission wires requires more and more high-voltage pylons, and sometimes, constructing pylons in mining areas is very urgent. To ensure the safe operation of pylons, coal pillars with large side lengths are usually used to provide sufficient support however, this results in a huge waste of coal. Eight high-voltage pylons are arranged on the ground surface corresponding to the location of working face 1110 of Sima Coal Mine in Shanxi Province, China, which cannot be mined by traditional methods. Taking this as the engineering background, the failure mode of high-voltage pylon is first analyzed. Using FLAC3D numerical simulations, the influence of five different mining plans on ground surface deformation in working face 1110 is evaluated, and the vertical settlement and horizontal deformation in different areas of the ground surface, as well as the variation law of horizontal strain and slope are analyzed. According to the numerical simulation results, the range of thickness-limiting mining or backfill mining in working face 1110 is shown in scheme 3, and the key regions in the mining process are determined. Secondly, the strengthening scheme of high-voltage pylons is designed, that is, the four foundations of high-voltage pylons are connected as a whole with steel supports and steel connectors so as to improve the structural strength of the high-voltage pylon. Finally, the position change in the foundation of high-voltage pylons was monitored for 22 consecutive months. The results show that the maximum settlement of the high-voltage tower foundation is 3.1 m, which is consistent with the actual mining thickness The high-voltage pylon was stably moved, and the change in transmission line tension and total length was usually less than 1.0%. The combined mining scheme and foundation strengthening scheme can ensure the safe operation of high-voltage pylons and provide a new method for the stability control of ground buildings in coal mining subsidence area.
Publisher: American Society of Civil Engineers (ASCE)
Date: 10-2023
Publisher: Elsevier BV
Date: 11-2023
Publisher: Springer Science and Business Media LLC
Date: 27-08-2016
Publisher: Wiley
Date: 24-02-2022
DOI: 10.1002/APP.52276
Abstract: Polyurethane grouting materials are increasingly used in the non‐excavation rehabilitation of roadbeds. The compressive strength of roadbed rehabilitation polyurethane (RHPU) grouting materials is the key to achieving the desirable repair effect, whereas the constitutive model of RHPU grouting materials is not yet understood. Here, the mechanical properties of RHPU grouting materials under compression were experimentally investigated, followed by establishing the hyperfoam constitutive model. The variation laws of the critical parameters in the model with density were function fitted, and then the constitutive model was simplified as an equation of density as the single independent variable. The comparisons between the theoretical and experimental mechanical behavior of RHPU grouting materials were discussed to illustrate the applicability of the hyperfoam constitutive model. Results show that with the increasing density, both the yield strength ( σ 1 ), elastic modulus ( E 1 ), and secant modulus ( E s ) increases exponentially, and the Poisson's ratio ( v ) increases logarithmically. The maximum increase in σ 1 , E 1 , E s , and v are about 750%, 720%, 940%, and 50%, respectively. Compared to the effects of density on the mechanical properties, the effect of loading rate is much smaller, and the side length has no effect. For RHPU s les with a density not exceeding 0.35 g/cm 3 , the hyperfoam model can well describe the uniaxial compression mechanical behavior, but for those whose density exceeds 0.35 g/cm 3 , the model can only describe the mechanical behavior before yielding. The theoretical yield strength of the RHPU s les obtained from the model is close to the experimental value (with differences of about 0.1%–14.4%). This study provides a base to evaluate the compressive strength of the practically used RHPU grouting materials based on the density.
Publisher: Springer Science and Business Media LLC
Date: 2023
Publisher: IOP Publishing
Date: 2021
DOI: 10.1088/1755-1315/643/1/012153
Abstract: In order to solve contact problems, ANSYS provides a variety of contact algorithms. However, there is no basis for how to select the contact algorithm when solving the contact problem in hydraulic structure engineering. Therefore, this paper introduces the basic concepts of contact algorithms briefly, such as penalty method, lagrange method, augmented lagrange method and L& P method, which are commonly used in ANSYS. Then, different ex les are used to compare the four contact algorithms in terms of accuracy, convergence and efficiency. Finally, considering the accuracy, convergence and efficiency, it is suggested to adopt L& P method in hydraulic structure contact analysis.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2021
Publisher: Elsevier BV
Date: 2023
DOI: 10.2139/SSRN.4436147
Publisher: Elsevier BV
Date: 2023
DOI: 10.2139/SSRN.4476489
Publisher: Elsevier BV
Date: 03-2016
Publisher: Elsevier BV
Date: 10-2022
Publisher: Elsevier BV
Date: 04-2023
Publisher: Elsevier BV
Date: 06-2021
Publisher: Elsevier BV
Date: 10-2019
Publisher: Elsevier BV
Date: 02-2022
Publisher: Springer Science and Business Media LLC
Date: 11-2017
Publisher: Elsevier BV
Date: 11-2022
Publisher: Elsevier BV
Date: 2023
DOI: 10.2139/SSRN.4503637
Publisher: Walter de Gruyter GmbH
Date: 2020
Abstract: Multi-walled carbon nanotubes (MWCNTs) have been added in the plain cementitious materials to manufacture composites with the higher mechanical properties and smart behavior. The uniform distributions of MWCNTs is critical to obtain the desired enhancing effect, which, however, is challenged by the high ionic strength of the cement pore solution. Here, the effects of methylcellulose (MC) on stabilizing the dispersion of MWCNTs in the simulated cement pore solution and the viscosity of MWCNT suspensions werestudied. Further observations on the distributions of MWCNTs in the ternary cementitious composites were conducted. The results showed that MC forms a membranous envelope surrounding MWCNTs, which inhibits the adsorption of cations and maintains the steric repulsion between MWCNTs thus, the stability of MWCNT dispersion in cement-based composites is improved. MC can also work as a viscosity adjuster that retards the Brownian mobility of MWCNTs, reducing their re-agglomerate within a period. MC with an addition ratio of 0.018 wt.% is suggested to achieve the optimum dispersion stabilizing effect. The findings here provide a way for stabilizing the other dispersed nano-additives in the cementitious composites.
Publisher: Elsevier BV
Date: 09-2021
Publisher: Elsevier BV
Date: 09-2021
Publisher: American Chemical Society (ACS)
Date: 06-04-2018
Publisher: SAGE Publications
Date: 11-06-2020
Location: No location found
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