scholarly journals Construction optimization of PBA of Subway station tunnel excavation and its cross section in loess area

2021 ◽  
Vol 791 (1) ◽  
pp. 012006
Author(s):  
Qingrui Chen ◽  
Xuanrong Zheng ◽  
Zhanbo Yin ◽  
Xuexuan Shang ◽  
Qi Lei ◽  
...  
Keyword(s):  
Cross Section ◽  
Subway Station ◽  
Tunnel Excavation ◽  
Loess Area ◽  
Construction Optimization

scholarly journals Influence of Small, Clear Distance Cross-Tunnel Blasting Excavation on Existing Tunnel below

2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Baofu Duan ◽  
Weizeng Gong ◽  
Guoshan Ta ◽  
Xuxu Yang ◽  
Xuewei Zhang
Keyword(s):  
Cross Section ◽  
Practical Significance ◽  
Blasting Vibration ◽  
Axial Distance ◽  
Tunnel Excavation ◽  
Vibration Effect ◽  
Blasting Excavation ◽  
Tunnel Blasting ◽  
Clear Distance ◽  
The Cross

The vibration effect generated during tunnel excavation can influence or damage adjacent tunnels. Studying and controlling the blasting vibration effect has important theoretical and practical significance, especially for new tunnels. This paper takes the tunnel project of Gao Jiu Lu-Jia Hua Cross Tunnel in Chongqing as the research background and assesses the blasting vibration influence in the up-down cross-tunnel. Onsite monitoring and numerical simulation were used to analyze peak particle velocity (PPV) changes, stress distribution, and crown settlement during the excavation process of Gao Jiu Lu I Tunnel at Jia Hua Tunnel Left Line in the cross-section. Influence laws of blasting excavation in a small, clear distance cross-tunnel on an existing tunnel below were obtained. Results show that new tunnel blasting vibrations exerted the largest influence on the crown of the existing tunnel below in the cross-section. The maximum tensile stress of the secondary lining of the existing tunnel below was mainly concentrated in the crown area. The maximum compressive stress during excavation was concentrated in the crown foot, and the stress value was less than the tensile and compressive strength of the concrete. The loosening of the surrounding rock from blasting excavation of the new tunnel caused secondary settlement of the existing tunnel crown below. The cumulative settlement value at the cross-section of the two tunnels was the largest. With an increase in axial distance from the cross-section of the existing tunnel crown, the settlement value gradually declined and became stable. These research results have reference value for the construction of a small, clear distance cross-tunnel and provide theoretical guidance for similar tunnel excavation projects in the future.

Optimization Analysis of Different Excavation Offsets in Railway Pilot Tunnel by CRD Method

2014 ◽  
Vol 505-506 ◽  
pp. 134-138
Author(s):  
Chun Kui Li
Keyword(s):  
Production Efficiency ◽  
Ground Surface ◽  
Simulation Method ◽  
Subway Station ◽  
Optimization Analysis ◽  
Tunnel Excavation ◽  
Construction Model ◽  
Surface Settlements ◽  
Stress Variations ◽  
Optimal Construction

This paper focuses on the construction of 10 railway pilot tunnels by CRD method in Jiefang Road subway station in Changchun. To achieve the optimal construction offsets during the pilot tunnel excavation, reduce the impacts of group cavern effect, and maximize the production efficiency, the construction model of railway pilot tunnel in subway station was created by the finite difference software Flac3D. The author used the numerical simulation method to analyze the ground surface settlements and the stress variations with three different construction offsets. Then the optimal construction offset was obtained. It could provide a theoretical guidance to the construction of a similar project.

scholarly journals Analytical Solutions for Tunnels of Elliptical Cross-Section in Rheological Rock Accounting for Sequential Excavation

2014 ◽  
Vol 48 (5) ◽  
pp. 1997-2029 ◽  
Author(s):  
H. N. Wang ◽  
S. Utili ◽  
M. J. Jiang ◽  
P. He
Keyword(s):  
Cross Section ◽  
Analytical Solutions ◽  
Viscoelastic Model ◽  
Integral Form ◽  
Ease Of Use ◽  
Elliptical Cross Section ◽  
Time Dependent ◽  
Tunnel Excavation ◽  
Elliptical Cross ◽  
Solid Media

AbstractTime dependency in tunnel excavation is mainly due to the rheological properties of rock and sequential excavation. In this paper, analytical solutions for deeply buried tunnels with elliptical cross-section excavated in linear viscoelastic media are derived accounting for the process of sequential excavation. For this purpose, an extension of the principle of correspondence to solid media with time varying boundaries is formulated for the first time. An initial anisotropic stress field is assumed. To simulate realistically the process of tunnel excavation, solutions are developed for a time-dependent excavation process with the major and minor axes of the elliptical tunnel changing from zero until a final value according to time-dependent functions specified by the designers. In the paper, analytical expressions in integral form are obtained assuming the incompressible generalized Kelvin viscoelastic model for the rheology of the rock mass, with Maxwell and Kelvin models solved as particular cases. An extensive parametric analysis is then performed to investigate the effects of various excavation methods and excavation rates. Also the distribution of displacements and stresses in space at different times is illustrated. Several dimensionless charts for ease of use of practitioners are provided.

Effect Analysis on Tunnel Serviceability State by the above Expressway Extension in Loess Area

2014 ◽  
Vol 919-921 ◽  
pp. 846-852
Author(s):  
Ke Guo Sun ◽  
Chao Kong ◽  
Wen Ge Qiu ◽  
Kai Liu ◽  
Wei Ping Xu ◽  
...  
Keyword(s):  
Cross Section ◽  
High Speed ◽  
Vertical Direction ◽  
Longitudinal Direction ◽  
Mutual Position ◽  
Tunnel Structure ◽  
Maximum Displacement ◽  
Effect Analysis ◽  
Loess Area ◽  
Unloading Effect

Based on the typical adjacent project of extension of LianHuo expressway which is constructed on WenXiang tunnel, the finite difference software, Flac3D, is adopted to stimulate the process of the construction. In this paper, from two aspects, the deformation of profile and cross-section, serviceability state is analyzed in detail. In the profile plot, usually displacement of the invert arch is less than that of the vault, and affected by the mutual position of topography and excavation, the maximum displacement, 6.3mm, merges at 50m of the vault in the profile plot; in the cross-section plot, due to occurrence of unloading effect brought by overlying excavation, tunnel structure has the tendency of rising toward the excavation. The calculated result shows that the displacement of WenXiang tunnel locating on the line of ZhengZhou-Xi’an Railway High-speed can be well controlled by adopting the excavation method of layering excavation at vertical direction and section excavation at longitudinal direction, which makes the safety of serviceability state of extension of expressway and the operation of Railway High-speed.

Tunnel Excavation Cross-Section Optimization by FEM under Feng-Tian Road in Chongqing

2014 ◽  
Vol 530-531 ◽  
pp. 932-935
Author(s):  
Cai Hua Huang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Cross Section ◽  
Railway Track ◽  
Tunnel Excavation ◽  
Optimal Scheme ◽  
Underground Railway ◽  
Simulation Results ◽  
Efficiency And Reliability ◽  
Element Method

With the development of transportation, subway is more and more important to every city, but the security of underground railway track faces with serious challenges. Tunnel excavation cross-section types have rectangle, roundness, arch, composite one and so on. In the tunnel excavation under Feng-tian Road in Chongqing, we chose three cross-section types for obtaining optimal scheme by finite element method (FEM). The efficiency and reliability of the optimized tunnel excavation cross-section were demonstrated by simulation results by FEM software Abaqus, and the tunnel excavation engineering under Feng-tian Road in Chongqing. Hope that this work can provide a reference to other tunnel excavation engineering.

XUV Absorption Spectra of Carbon Ions

1988 ◽  
Vol 102 ◽  
pp. 71-73
Author(s):  
E. Jannitti ◽  
P. Nicolosi ◽  
G. Tondello
Keyword(s):  
Absorption Spectra ◽  
Cross Section ◽  
Theoretical Calculations ◽  
Photoionization Cross Section ◽  
Carbon Ions

AbstractThe photoabsorption spectra of the carbon ions have been obtained by using two laser-produced plasmas. The photoionization cross-section of the CV has been absolutely measured and the value at threshold, σ=(4.7±0.5) × 10−19cm2, as well as its behaviour at higher energies agrees quite well with the theoretical calculations.

Elastic Scattering in Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 252-253
Author(s):  
J. Langmore ◽  
M. Isaacson ◽  
J. Wall ◽  
A. V. Crewe
Keyword(s):  
Electron Microscopy ◽  
Elastic Scattering ◽  
Cross Section ◽  
Quantum Noise ◽  
Dark Field ◽  
Elastic Cross Section ◽  
Biological Molecules ◽  
Dark Field Microscopy ◽  
Field Systems ◽  
Effects Of Radiation

High resolution dark field microscopy is becoming an important tool for the investigation of unstained and specifically stained biological molecules. Of primary consideration to the microscopist is the interpretation of image Intensities and the effects of radiation damage to the specimen. Ignoring inelastic scattering, the image intensity is directly related to the collected elastic scattering cross section, σɳ, which is the product of the total elastic cross section, σ and the eficiency of the microscope system at imaging these electrons, η. The number of potentially bond damaging events resulting from the beam exposure required to reduce the effect of quantum noise in the image to a given level is proportional to 1/η. We wish to compare η in three dark field systems.

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