scholarly journals Numerical simulation analysis of tunnel construction mechanical response considering shotcrete hardening process

2021 ◽  
Vol 2045 (1) ◽  
pp. 012026
Author(s):  
Z H Nie ◽  
X G Jin ◽  
W Luo
Keyword(s):  
Growth Rate ◽  
Mechanical Response ◽  
Simulation Analysis ◽  
Early Stage ◽  
Surrounding Rock ◽  
Model Parameters ◽  
Tunnel Construction ◽  
Chemical Corrosion ◽  
Finite Element Software ◽  
Hardening Process

Abstract At present, tunnel construction mechanics studies basically do not consider the hardening process of shotcrete. In order to reveal the hardening process of sprayed concrete in a sulfate environment and the influence of sulfate corrosion on tunnel stability, the model parameters were determined in combination with the change rules of mechanical parameters of shotcrete obtained in the author’s experiment. The MIDAS GTSNX finite element software was used to analyze the effect of the hardening process of the shotcrete, chemical corrosion, and physical corrosion of sulfate on the displacement and stress of the surrounding rock of the tunnel. The results show that considering the hardening process of shotcrete, the growth rate of tunnel clearance displacement increases, and the stress increase slows in the early stage of shotcrete (The tunnel lining structure is applied, and the second step of excavation is carried out). With the increase of time or the construction steps, the stress of shotcrete increases significantly, and the clearance displacement growth rate significantly decreased. The influence of the chemical and physical corrosion of shotcrete on the stress and displacement of the surrounding rock of the tunnel is similar to considering the hardening process of shotcrete. indicating that sulfate corrosion has an inhibitory effect on the hardening process of shotcrete and increased construction risk.

scholarly journals Research and Analysis on the Influence of Small Clear Distance Drilling and Blasting Method on the Existing Tunnel Structure

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Haibin Huang ◽  
Peng Li ◽  
Chuang Wang ◽  
Bingxiang Yuan ◽  
Minjie Chen ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Simulation Analysis ◽  
Peak Load ◽  
Vertical Displacement ◽  
Tunnel Construction ◽  
Finite Element Software ◽  
Resultant Velocity ◽  
Clear Distance ◽  
Under Construction ◽  
Blasting Method

In order to study the vibration influence of tunnel drilling and blasting method on the built tunnel with small clear distance, taking the intersection of Zhuhai Dahengqinshan No. 1 tunnel and Zhuji urban rail tunnel as the engineering background, we used ABAQUS finite element software to conduct numerical simulation analysis on the influence of different blasting loads on existing tunnels with small clear distance in Zhuji tunnel construction. The following conclusions were drawn: the blasting construction of the tunnel under construction had the greatest impact on the vault of the existing tunnel; when the peak load was reduced by half, the stress value, vertical displacement, and resultant velocity of Mises were also reduced by half, which indicates that reducing the peak value of blasting load appropriately can ensure the safety of tunnel construction. When the peak load is 2.7 MPa, the measured and simulated values were less than the resultant velocity limit required by the specification. In addition, the relative error between the measured value and the simulated value was less than 5%, indicating the accuracy of the numerical simulation.

scholarly journals Stability Analysis and Protection Measures of Large Section Tunnel in Coal Rich Weak Rock Stratum

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Guannan Zhou ◽  
Zijiang Zhao ◽  
Zhanping Song ◽  
Hongjian Wang
Keyword(s):  
Coal Seam ◽  
Large Scale ◽  
Economic Benefits ◽  
Surrounding Rock ◽  
Tunnel Construction ◽  
Weak Rock ◽  
Large Section ◽  
Tunnel Face ◽  
Finite Element Software ◽  
Geological Conditions

Due to poor engineering geological conditions of Liujiazhuang tunnel on Shanghai-Kunming Passenger Dedicated Line, the large deformation of weak rock occurs repeatedly during tunnel construction. In this paper, the large-scale finite element software ABAQUS is used to simulate the construction process of a large-section tunnel in weak surrounding rock. It is found that when tunnel face passes through the coal seam, the displacement and stress simulated by the bench method increase abruptly. The maximum stress reaches up to 18 MPa, and displacement reaches 45 mm, which is about twice when without crossing coal seam. It is technically feasible to use the bench method for tunnel construction, under the condition when large settlements is allowed; additionally, the bench method has better technical and economic benefits than that of the CD method. Through the comparative analysis of onsite monitoring data and numerical simulation results, it can be seen that the tunnel is in a dangerous state when passing through the coal seam and measures such as strengthening support or auxiliary advance support should be taken immediately to control the surrounding rock and to ensure tunnel construction safety.

scholarly journals Incipient Bulk Polycrystal Plasticity Observed by Synchrotron in-situ Topotomography

2018 ◽  
Author(s):  
Henry Proudhon ◽  
Nicolas Gueninchault ◽  
Samuel Forest ◽  
Wolfgang Ludwig
Keyword(s):  
Slip System ◽  
Mechanical Response ◽  
Early Stage ◽  
Model Parameters ◽  
X Ray Diffraction ◽  
X Ray ◽  
Polycrystal Plasticity ◽  
System Activation ◽  
The Individual

In this paper, we present a comprehensive 4D study of the early stage of plastic deformation in a polycrystalline binary AlLi alloy. The entire microstructure is mapped with X-ray diffraction contrast tomography and a set of bulk grains is further studied via X-ray topotomography during mechanical loading. The observed contrast is analyzed with respect to the slip system activation and the evolution of the orientation spread is measured as a function of applied strain. The experimental observations are augmented by the mechanical response predicted by crystal plasticity finite element simulations to analyze the onset of plasticity in details. Simulation results show a general agreement of the individual slip system activation during loading and that comparison with experiments at the length scale of the grains may be used to fine tune the constitutive model parameters.

scholarly journals Incipient Bulk Polycrystal Plasticity Observed by Synchrotron In-Situ Topotomography

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2018 ◽  
Author(s):  
Henry Proudhon ◽  
Nicolas Guéninchault ◽  
Samuel Forest ◽  
Wolfgang Ludwig
Keyword(s):  
Slip System ◽  
Mechanical Response ◽  
Early Stage ◽  
Model Parameters ◽  
X Ray Diffraction ◽  
X Ray ◽  
Polycrystal Plasticity ◽  
System Activation ◽  
The Individual

In this paper, we present a comprehensive 4D study of the early stage of plastic deformation in a polycrystalline binary AlLi alloy. The entire microstructure is mapped with X-ray diffraction contrast tomography, and a set of bulk grains is further studied via X-ray topotomography during mechanical loading. The observed contrast is analyzed with respect to the slip system activation, and the evolution of the orientation spread is measured as a function of applied strain. The experimental observations are augmented by the mechanical response predicted by crystal plasticity finite element simulations to analyze the onset of plasticity in detail. Simulation results show a general agreement of the individual slip system activation during loading and that comparison with experiments at the length scale of the grains may be used to fine tune the constitutive model parameters.

Pattern Formation in Thin Polymer Films: A New Morphology

2000 ◽  
Vol 629 ◽  
Author(s):  
Jean-Loup Masson ◽  
Peter F. Green
Keyword(s):  
Growth Rate ◽  
Pattern Formation ◽  
Early Stage ◽  
Structural Evolution ◽  
Distinct Form ◽  
Thin Polymer Films ◽  
Intermediate Morphology ◽  
Thin Polymer ◽  
Nonwetting Liquid ◽  
Cylindrical Holes

ABSTRACTResearchers have shown that thin, nonwetting, liquid homopolymer films dewet substrates, forming patterns that reflect fluctuations in the local film thickness. These patterns have been shown to be either discrete cylindrical holes or bicontinuous “spinodal-like” patterns. In this paper we show the existence of a new morphology. During the early stage of dewetting, discrete highly asymmetric holes appear spontaneously throughout the film. The nucleation rate of these holes is faster than their growth rate. The morphology of the late stage of evolution, after 18 days, is characterized by a bicontinuous pattern, distinct form conventional spinodal dewetting patterns. This morphology has been observed for a range of film thicknesses between 7.5 and 21nm. The structural evolution of this intermediate morphology is discussed.

A modeling approach to simulate impact of climate change in lake water quality: phytoplankton growth rate assessment

1998 ◽  
Vol 37 (2) ◽  
pp. 177-185 ◽  
Author(s):  
Hany Hassan ◽  
Keisuke Hanaki ◽  
Tomonori Matsuo
Keyword(s):  
Climate Change ◽  
Water Quality ◽  
Growth Rate ◽  
Dissolved Oxygen ◽  
Lake Water ◽  
Phytoplankton Growth ◽  
Quality Data ◽  
Model Parameters ◽  
Lake Water Quality ◽  
Phytoplankton Growth Rate

Global climate change induced by increased concentrations of greenhouse gases (especially CO2) is expected to include changes in precipitation, wind speed, incoming solar radiation, and air temperature. These major climate variables directly influence water quality in lakes by altering changes in flow and water temperature balance. High concentration of nutrient enrichment and expected variability of climate can lead to periodic phytoplankton blooms and an alteration of the neutral trophic balance. As a result, dissolved oxygen levels, with low concentrations, can fluctuate widely and algal productivity may reach critical levels. In this work, we will present: 1) recent results of GCMs climate scenarios downscaling project that was held at the University of Derby, UK.; 2) current/future comparative results of a new mathematical lake eutrophication model (LEM) in which output of phytoplankton growth rate and dissolved oxygen will be presented for Suwa lake in Japan as a case study. The model parameters were calibrated for the period of 1973–1983 and validated for the period of 1983–1993. Meterologic, hydrologic, and lake water quality data of 1990 were selected for the assessment analysis. Statistical relationships between seven daily meteorological time series and three airflow indices were used as a means for downscaling daily outputs of Hadley Centre Climate Model (HadCM2SUL) to the station sub-grid scale.

Numerical solutions for strain-softening surrounding rock under three-dimensional principal stress condition

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sheng Yu-ming ◽  
Li Chao ◽  
Xia Ming-yao ◽  
Zou Jin-feng
Keyword(s):  
Finite Element ◽  
Principal Stress ◽  
Stress Condition ◽  
Strain Softening ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Strength Criterion ◽  
Surrounding Rock ◽  
Flow Rule ◽  
Finite Element Software

Abstract In this study, elastoplastic model for the surrounding rock of axisymmetric circular tunnel is investigated under three-dimensional (3D) principal stress states. Novel numerical solutions for strain-softening surrounding rock were first proposed based on the modified 3D Hoek–Brown criterion and the associated flow rule. Under a 3D axisymmetric coordinate system, the distributions for stresses and displacement can be effectively determined on the basis of the redeveloped stress increment approach. The modified 3D Hoek–Brown strength criterion is also embedded into finite element software to characterize the yielding state of surrounding rock based on the modified yield surface and stress renewal algorithm. The Euler implicit constitutive integral algorithm and the consistent tangent stiffness matrix are reconstructed in terms of the 3D Hoek–Brown strength criterion. Therefore, the numerical solutions and finite element method (FEM) models for the deep buried tunnel under 3D principal stress condition are presented, so that the stability analysis of surrounding rock can be conducted in a direct and convenient way. The reliability of the proposed solutions was verified by comparison of the principal stresses obtained by the developed numerical approach and FEM model. From a practical point of view, the proposed approach can also be applied for the determination of ground response curve of the tunnel, which shows a satisfying accuracy compared with the measuring data.

scholarly journals Public Compliance With Social Distancing Measures and SARS-CoV-2 Spread

2021 ◽  
pp. 003335492110112
Author(s):  
Hongjie Liu ◽  
Chang Chen ◽  
Raul Cruz-Cano ◽  
Jennifer L. Guida ◽  
Minha Lee
Keyword(s):  
Growth Rate ◽  
Reproduction Number ◽  
Early Stage ◽  
Human Mobility ◽  
The United States ◽  
Density Change ◽  
Regression Coefficients ◽  
Daily Growth Rate ◽  
Daily Growth ◽  
Social Distancing

Objective We quantified the association between public compliance with social distancing measures and the spread of SARS-CoV-2 during the first wave of the epidemic (March–May 2020) in 5 states that accounted for half of the total number of COVID-19 cases in the United States. Methods We used data on mobility and number of COVID-19 cases to longitudinally estimate associations between public compliance, as measured by human mobility, and the daily reproduction number and daily growth rate during the first wave of the COVID-19 epidemic in California, Illinois, Massachusetts, New Jersey, and New York. Results The 5 states mandated social distancing directives during March 19-24, 2020, and public compliance with mandates started to decrease in mid-April 2020. As of May 31, 2020, the daily reproduction number decreased from 2.41-5.21 to 0.72-1.19, and the daily growth rate decreased from 0.22-0.77 to –0.04 to 0.05 in the 5 states. The level of public compliance, as measured by the social distancing index (SDI) and daily encounter-density change, was high at the early stage of implementation but decreased in the 5 states. The SDI was negatively associated with the daily reproduction number (regression coefficients range, –0.04 to –0.01) and the daily growth rate (from –0.009 to –0.01). The daily encounter-density change was positively associated with the daily reproduction number (regression coefficients range, 0.24 to 1.02) and the daily growth rate (from 0.05 to 0.26). Conclusions Social distancing is an effective strategy to reduce the incidence of COVID-19 and illustrates the role of public compliance with social distancing measures to achieve public health benefits.

Numerical Simulation on the Effect of Compound Roof Separation Position on Bolting Performance

2014 ◽  
Vol 953-954 ◽  
pp. 1638-1642
Author(s):  
Ai Qing Liu ◽  
Jian Zhang ◽  
Peng Cheng ◽  
Yu Hai Zhang
Keyword(s):  
Numerical Simulation ◽  
Simulation Analysis ◽  
Surrounding Rock ◽  
Cohesive Force ◽  
Roof Strata ◽  
Poor Stability ◽  
Key Parameter

Prestress is a key parameter in bolting, while the cohesive force of layers in the compound roof strata is low and prone to separation, causing the prestress proliferation very poor. With the method of numerical simulation analysis,the location of separation in compound roof to affect the performance of bolting support was researched. It is concluded the roof separation in the edge of anchorage zone, the prestress field superpose, but is away from the deep surrounding rock and shows poor stability,however the role of cable can make up for the defect of rockbolts support. It has been found the highly prestressed strength bolting system adapts to the compound roof.

Numerical Simulation on Heat Dissipating Performance of New Pipe with Grid Plate

2012 ◽  
Vol 532-533 ◽  
pp. 417-421
Author(s):  
Chang Li Song ◽  
Jing Ji
Keyword(s):  
Heat Transfer ◽  
Simulation Analysis ◽  
Heat Transfer Analysis ◽  
Finite Element Software ◽  
Grid Plate ◽  
Steady State Heat ◽  
Steady State Heat Transfer ◽  
Energy Conservation Law ◽  
Optimal Diameter ◽  
Selection Of

In order to improve the pipe dissipating area, a kind of new pipe with grid plate is proposed in this paper. Based on the basic principle of heat transfer and energy conservation law, by finite element software ANSYS the simulation analysis of the steady-state heat transfer of the new pipeline is carried out, process of ANSYS modeling, loading and solving is introduced in detail, the distribution of temperature and stress for pipe with a grid plate is given, these can provide the foundation for the selection of the optimal diameter of the grid plate and transient heat transfer analysis of pipe.

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