scholarly journals Research on Construction Methods for Ultralarge Y-Shaped Tunnel Sections

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Shiding Cao ◽  
Yongli Xie ◽  
Wei Tang ◽  
Wei Wang ◽  
Qianru Zhou ◽  
...  
Keyword(s):  
Stability Criterion ◽  
Abrupt Change ◽  
Internal Force ◽  
Special Method ◽  
Large Section ◽  
Large Span ◽  
Construction Methods ◽  
Excavation Process ◽  
Clear Distance ◽  
The Stability

Many problems are encountered in the construction of bifurcated tunnels due the abrupt change in section, small clear distance, and large section. Progress in the direction of tunnel construction is limited by the large-span section; therefore, a special method of construction that involves constructing a guiding tunnel first followed by reverse excavation was adopted to construct the large-span bifurcation section of the Liantang tunnel of Shenzhen Eastern Transit Expressway in China. The stability criterion of the surrounding rock of the middle wall in the section of multiple arch and small clear distance is studied by theoretical analysis, and the internal stress and corresponding ultimate strength of the middle wall under different buried depths and widths of the middle wall are calculated by the stability criterion. In this study, 3D finite-difference software was used to simulate the excavation process under forward and reverse excavation conditions. The results show that the displacement field and internal force field distribution are similar for both excavation methods, and the tunneling first and reverse excavation construction method is safe and reliable.

scholarly journals Dynamic Numerical Analysis of Displacement Restraining Effect of Inclined Earth-Retaining Structure during Embankment Construction

2019 ◽  
Vol 9 (11) ◽  
pp. 2213 ◽  
Author(s):  
Su-Won Son ◽  
Minsu Seo ◽  
Jong-Chul Im ◽  
Jae-Won Yoo
Keyword(s):  
Numerical Analysis ◽  
Maximum Stress ◽  
Lateral Displacement ◽  
Retaining Wall ◽  
Field Tests ◽  
Front Wall ◽  
Construction Process ◽  
Construction Methods ◽  
Excavation Process ◽  
The Stability

Retaining walls are generally used for temporary installations during the excavation process of a construction project. They are also utilized to construct embankments in order to extend a railway facility. In this case, a retaining wall is installed during the construction process and contributes to the resistance of large amounts of stress, including the railway load. However, it is generally difficult to retain walls to maintain their stability. Therefore, alternative construction methods, such as the use of an inclined earth-retaining wall, have been utilized to suppress the lateral displacement. The stability is verified in advance through field tests; however, the maximum stress acting on the railway is thought to be the concentrated railway load. In this study, a two-dimensional numerical analysis was conducted by changing the railway load to a dynamic load. The analysis was applied according to the number of H-piles of the same length (10 m) when only the front wall was installed and when a back support was also applied. It was determined that the lateral displacement of the latter case is smaller than that of the former, whereas the resistance to dynamic loading of the former case is greater.

scholarly journals Study on Identification of Construction Method for Ultra-Large-Span Tunnel

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Xu Chongbang ◽  
Qin Youlin
Keyword(s):  
Rock Strength ◽  
Construction Method ◽  
Surrounding Rock ◽  
Orthogonal Test ◽  
Tunnel Construction ◽  
Test Model ◽  
Large Span ◽  
Construction Methods ◽  
The Stability

Although the determination of tunnel construction methods is extremely critical for the construction of ultra-large-span tunnels, the determination of construction methods is still at a qualitative level, which relies on the engineering experience of on-site technicians and lacks rigorous and systematic theoretical basis and technical standards. By means of orthogonal test method, the proper construction method was established for the deep-buried ultra-large-span tunnel where the tunnel excavation span, tunnel surrounding rock strength, and rock integrity coefficient were set as the main control factors. The stability of tunnel surrounding rock under various test conditions was quantified according to the plastic zone properties calculated by the three-factor and five-level orthogonal test model. Meanwhile, the macro form and quantitative method of test combinations under different levels of various factors were proposed to obtain the influence of each factor on the stability of tunnel surrounding rock, and thus the functional relations between various factors and tunnel stability were obtained. On this basis, the identification and the criterion of the ultra-large-span tunnel construction method were established, which can quantitatively reflect the contribution of excavation span of the tunnel, the number of lateral drifts in cross section, surrounding rock strength, and rock integrity coefficient to surrounding rock stability of the tunnel. The construction method calculation results of the Malin tunnel, a practical underground project, are obtained according to the orthogonal test model calculation. Based on the method, Malin tunnel can be constructed safely and efficiently. The research results could provide the theoretical basis for the identification and selection of construction method for ultra-large-span tunnel.

The Construction Process Simulation of a Large-Span Rhombic Space Truss Using FEM Analysis

2011 ◽  
Vol 368-373 ◽  
pp. 1101-1104
Author(s):  
Xu Yan ◽  
Tie Ying Li ◽  
Yun Jing Nie
Keyword(s):  
Fem Analysis ◽  
Construction Process ◽  
Large Span ◽  
Construction Design ◽  
Construction Methods ◽  
The North ◽  
Space Truss ◽  
Design Theories ◽  
The Stability ◽  
Space Trusses

With the developments of the design theories and the researches, the quantity and the technology of space truss systems in our country have reached the international leading level. In the meantime, the construction methods need to achieve even higher standard. In the article, the rhombic space truss roof of the north station building of Suzhou is selected as the research object. Each step of the sliding and unloading construction is simulated by FEM. The stability and rigidity of the truss are checked in detail. It gives an representative exsample for complicated construction design of large-span space trusses.

The Numerical Simulation Analysis of Excavation Process of Loess Tunnel

2011 ◽  
Vol 383-390 ◽  
pp. 6594-6600 ◽  
Author(s):  
Jian Guo ◽  
Qi Cai Wang
Keyword(s):  
Numerical Simulation ◽  
Simulation Analysis ◽  
Internal Force ◽  
Design Parameters ◽  
Construction Process ◽  
The Finite Element Method ◽  
Excavation Process ◽  
Internal Forces ◽  
The Stability ◽  
Method Construction

The bench method dynamic construction process of Xin Baotashan tunnel which located in the grade IV surrounding rock is simulated by using the finite element method. The variation of displacement and stress field of the surrounding rocks and the internal force of the lining structures during every excavation step is calculated. The state of the surrounding rocks can be predicted by the numerical simulation results, and the construction plan and construction sequences can be guided by the analysis results. At the same time the reasonability and feasibility of the design parameters can be judged by analyzing the internal forces of the lining structures. Analysis and experimental results showed that the stability of the surrounding rocks is good by using the bench method construction to the IV grade surrounding rocks and the design parameters of the lining structures are feasible.

scholarly journals Study on instability failure mode and monitoring early warning standard of surrounding rock in fully weathered argillaceous sandstone section of large section tunnel

2019 ◽  
Vol 136 ◽  
pp. 04023
Author(s):  
Ming Zhao ◽  
Ke Li ◽  
Hong Yan Guo ◽  
KaiCheng Hua
Keyword(s):  
Limit State ◽  
Stable State ◽  
Simulation Software ◽  
Surrounding Rock ◽  
Large Section ◽  
Rock Stability ◽  
Geological Conditions ◽  
Construction Step ◽  
The Face ◽  
The Stability

Based on the special geological conditions of a tunnel in Qingyuan section of Huizhou-Zhanzhou Expressway, FLAC3d numerical simulation software is used to simulate the rheological properties and instability of surrounding rock in large-section fully weathered sandstone section, and the stability and loss of surrounding rock are analyzed. The deformation of the dome and the face at steady state is analyzed. It is found that: 1) when the surrounding rock is in a stable state, the deformation curve of the dome is smooth. When the surrounding rock of the face is unstable, the front of the face appears ahead. Deformation should be first strengthened on the surrounding rock in front of the face. 2) The arched foot is an important part of the instability of the surrounding rock. In order to prevent the expansion of the collapsed part, the arched part should be reinforced. 3) In order to obtain the limit state of surrounding rock stability, the strength of surrounding rock is reduced, and the strength reduction coefficient corresponding to the displacement sudden point is taken as the safety factor of rock stability around the hole, and the stability safety coefficients of surrounding rock of each construction step are greater than 1.2. 4) The dynamic standard values of deformation control in the whole construction stage are obtained by analyzing the deformation curves of each data monitoring point with time in the corresponding time period of each construction step.

Intrinsic Thermal Stability of Anisotropic Thin-Film Superconductors

1990 ◽  
Vol 112 (1) ◽  
pp. 10-15 ◽  
Author(s):  
M. I. Flik ◽  
C. L. Tien
Keyword(s):  
Thin Film ◽  
Thermal Stability ◽  
Stability Criterion ◽  
High Temperature Superconductors ◽  
Stability Criteria ◽  
Anisotropic Thermal Conductivity ◽  
Operating Current ◽  
Released Energy ◽  
The Stability ◽  
Thermal Stability Of

Intrinsic thermal stability denotes a situation where a superconductor can carry the operating current without resistance at all times after the occurrence of a localized release of thermal energy. This novel stability criterion is different from the cryogenic stability criteria for magnets and has particular relevance to thin-film superconductors. Crystals of ceramic high-temperature superconductors are likely to exhibit anisotropic thermal conductivity. The resultant anisotropy of highly oriented films of superconductors greatly influences their thermal stability. This work presents an analysis for the maximum operating current density that ensures intrinsic stability. The stability criterion depends on the amount of released energy, the Biot number, the aspect ratio, and the ratio of the thermal conductivities in the plane of the film and normal to it.

The flow of a micropolar liquid layer down an inclined plane

1968 ◽  
Vol 64 (2) ◽  
pp. 513-526 ◽  
Author(s):  
A. J. Willson
Keyword(s):  
Thin Films ◽  
Steady State ◽  
Liquid Layer ◽  
Stability Criterion ◽  
Long Waves ◽  
Inclined Plane ◽  
The Stability ◽  
Micropolar Liquid

AbstractConsideration is given to the flow of a micropolar liquid down an inclined plane. The steady state is analysed and Yih's technique is employed in an investigation of the stability of this flow with respect to long waves. Detailed calculations are given for thin films and it is shown that the micropolar properties of the liquid play an important role in the stability criterion.

The Meniscus Instability of a Thin Liquid Film

1988 ◽  
Vol 55 (4) ◽  
pp. 975-980 ◽  
Author(s):  
H. Koguchi ◽  
M. Okada ◽  
K. Tamura
Keyword(s):  
Thin Film ◽  
Analytical Solution ◽  
Liquid Film ◽  
Tilt Angle ◽  
Stability Criterion ◽  
Thin Liquid Film ◽  
Normal Direction ◽  
Wave Number ◽  
The Stability ◽  
Maximum Amplification

This paper reports on the instability for the meniscus of a thin film of a very viscous liquid between two tilted plates, which are separated at a constant speed with a tilt angle in the normal direction of the plates. The disturbances on the meniscus moving with movement of the plates are examined experimentally and theoretically. The disturbances are started when the velocity of movement of the plates exceeds a critical one. The wavelength of the disturbances is measured by using a VTR. The instability of the meniscus is studied theoretically using the linearized perturbation method. A simple and complete analytical solution yields both a stability criterion and the wave number for a linear thickness geometry. These results compared with experiments for the instability show the validity of the stability criterion and the best agreement is obtained with the wave number of maximum amplification.

Walking Stability Analysis of Multi-Legged Crablike Robot over Slope

2013 ◽  
Vol 572 ◽  
pp. 636-639
Author(s):  
Xi Chen ◽  
Gang Wang
Keyword(s):  
Mathematical Model ◽  
Stability Analysis ◽  
Stability Criterion ◽  
Stability Margin ◽  
Static Stability ◽  
Matlab Simulation ◽  
And Performance ◽  
The Stability ◽  
The Mathematical Model ◽  
The Relationship

This paper deals with the walking stability analysis of a multi-legged crablike robot over slope using normalized energy stability margin (NESM) method in order to develop a common stabilization description method and achieve robust locomotion for the robot over rough terrains. The robot is simplified with its static stability being described by NESM. The mathematical model of static stability margin is built so as to carry out the simulation of walking stability over slope for the crablike robot that walks in double tetrapod gait. As a consequence, the relationship between stability margin and the height of the robots centroid, as well as its inclination relative to the ground is calculated by the stability criterion. The success and performance of the stability criterion proposed is verified through MATLAB simulation and real-world experiments using multi-legged crablike robot.

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