scholarly journals Combined Application of Pipe Roof Pre-SUPPORT and Curtain Grouting Pre-Reinforcement in Closely Spaced Large Span Triple Tunnels

2020 ◽  
Vol 10 (9) ◽  
pp. 3186
Author(s):  
Ran Li ◽  
Dingli Zhang ◽  
Peng Wu ◽  
Qian Fang ◽  
Ao Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Field Application ◽  
In Situ Monitoring ◽  
Tunnel Face ◽  
Large Span ◽  
Combined Application ◽  
Time Space ◽  
Curtain Grouting ◽  
Plastic Ratio ◽  
Underground Station

The platform of the Badaling Great Wall Underground Station consisted of large span triple tunnels. The triple tunnels passed through several major faults. Based on preliminary in situ monitoring, the interaction behavior among triple tunnels was significantly severe, and the original supports failed to meet the safety requirement. Therefore, pipe roof pre-support (PRPS) and curtain grouting pre-reinforcement (CGPR) were used as the pre-construction techniques. By numerical investigation, the pipe diameter, the arrangement angle of PRPS, and the grouting thickness of CGPR were optimized as 108 mm, 150°, and 3 m, respectively. According to numerical results, PRPS predominantly bore loose rock and reduced mean crown settlement (MCS), while CGPR primarily improved the mechanical properties of rock and decreased the pillar plastic ratio (PPR). PRPS and CGPR had complementary advantages in time, space, and mechanical properties. PRPS could timely form a strong arch structure far ahead of the tunnel face, CGPR could effectively restrict the development of plastic zone. They mutually and actively formed a strong permanent ring in front of the tunnel face. After the field application of PRPS and CGPR, the mean surrounding rock pressure reduced by 33.4%, the MCS reduced by 58.7%, and no support damage was observed. The excavation safety was guaranteed.

Study on In Situ Monitoring of the Surrounding Rock Pressure of the Shallow Large-Span Tunnel in the Tunnel Construction Process

2011 ◽  
Vol 413 ◽  
pp. 454-458
Author(s):  
Xin Zhi Li ◽  
Shu Cai Li ◽  
Ying Yong Li ◽  
Shu Chen Li
Keyword(s):  
Rock Pressure ◽  
Surrounding Rock ◽  
In Situ Monitoring ◽  
Tunnel Engineering ◽  
Tunnel Face ◽  
Tunnel Excavation ◽  
Large Span ◽  
Parallel Tunnel ◽  
Surrounding Rock Pressure

The surrounding rock pressure which was determined effectively through in-situ monitoring was the important parametric of the tunnel engineering design.According to in-situ monitoring of the surrounding rock pressure in the relied engineering . The adjustment and distribution characteristics of surrounding rock pressure of the shallow large-span tunnel with three-level seven-step parallel tunnel excavation was studied, the results showed that the arch and sides of the tunnel arch foot were the key parts which concentrated the surrounding rock pressure. The adjustment and distribution of surrounding rock pressure had not obvious relationships with tunnel face distance. Finally, the composite factors that impacted monitoring results of the surrounding rock pressure was analysed. The results had great significance on the development and perfection of the surrounding rock pressure theory in shallow large-span tunnel.

Research on Deformation Mechanism of Surrounding Rock during Excavation of Large-Span Shallow-Buried Double-Arch Tunnel

2013 ◽  
Vol 392 ◽  
pp. 890-894
Author(s):  
Shao Rui Sun ◽  
Ye Xu Lu ◽  
Shao Hua Zhang ◽  
Ji Min Wu
Keyword(s):  
Deformation Mechanism ◽  
Back Analysis ◽  
Ground Surface ◽  
Surrounding Rock ◽  
Tunnel Excavation ◽  
Large Span ◽  
Main Work ◽  
Time Space ◽  
Space Effect ◽  
Force Mechanism

The deformation mechanism of surrounding rock during excavation is difficult to stability evaluation for large-span shallow-buried double-arch tunnel. Take Fenghuang mountain tunnel in Suzhou city as an example, the main work and funding are as follow: The measured data in the middle of the tunnel, including settlement on the top of the tunnel and deformation between two lateral walls, were used to calculate mechanical parameters by back analysis method. The obtained parameters were used to calculate the deformation and stress of the main tunnel excavation in the different steps. The rules includes time-space effect during main tunnel excavation, force mechanism of the middle wall and settlement on the ground surface for the surrounding rock in the main tunnel. Finally, the calculated settlement and deformation were compared to the monitoring results. The safety coefficient of surrounding rock for double-arch tunnel was obtained by strength reduction theory.

Lightweight Aggregate Concrete as an Alternative for Dense Concrete in Post-Tensioned Concrete Slab

2018 ◽  
Vol 926 ◽  
pp. 140-145 ◽  
Author(s):  
Małgorzata Mieszczak ◽  
Lucyna Domagała
Keyword(s):  
Mechanical Properties ◽  
Lightweight Concrete ◽  
Concrete Slab ◽  
Lightweight Aggregate ◽  
Lightweight Aggregate Concrete ◽  
Aggregate Concrete ◽  
Large Span ◽  
Shrinkage And Creep ◽  
Theoretical Results ◽  
Post Tensioned

The paper presents the results of tests conducted on two lightweight aggregate concretes made of new national Certyd artificial aggregate. This research is intended to first application of lightweight concrete to construct large-span post-tensioned slab. In addition to mechanical properties development, shrinkage and creep during 3 months of loading were tested. The obtained results are compared with theoretical results predicted by standard. Conducted tests indicated, that measured values of shrinkage and creep are significantly lower than predicted ones. This is promise for application of tested concrete in construction of post-tensioned slabs.

scholarly journals Displacement Characteristics of an Urban Tunnel in Silty Soil by the Shallow Tunnelling Method

2020 ◽  
Vol 2020 ◽  
pp. 1-16 ◽  
Author(s):  
Shaobing Zhang ◽  
Siyue He ◽  
Junling Qiu ◽  
Wei Xu ◽  
Rodney Sheldon Garnes ◽  
...  
Keyword(s):  
Soil Surface ◽  
Surface Settlement ◽  
In Situ Monitoring ◽  
Good Effect ◽  
Shallow Tunnel ◽  
Tunnel Face ◽  
Face Surface ◽  
Silty Soil ◽  
Construction Methods ◽  
Jet Grouting

The urban shallow tunnelling process in silty soil is easy to cause large displacement of surface and tunnel. Obviously, if the strata and the tunnel face are not treated by reasonable reinforcement method, instability and collapse phenomenon will be encountered during the tunnel excavation. There are a series of studies on construction methods of shallow tunnels, but these methods have limitations in silty soil. In this study, a comprehensive construction plan of the urban shallow tunnel in silty soil was proposed and applied to a case study in Fuzhou, Fujian Province in South China. The in situ monitoring tests and numerical simulation were employed to address displacement characteristics of surface and tunnel. Results indicated that the urban shallow tunnelling process could achieve good effect by dewatering of silty soil, reinforcing surface by vertical jet grouting piles, and advanced small pipes and circumferential grouting in the tunnel face; surface settlement during dewatering process accounted for about 30% of total surface settlement in silty soil; the excavation of the top heading, the middle, and lower benches had great effect on displacement of surface and tunnel for three-bench seven-step excavation method in silty soil; surface settlement troughs in silty soil were deeper and wider; lock-feet bolts had good effect on restricting horizontal convergence; and ratio of total crown settlement and total horizontal convergence was in range of 1.43∼1.59 when b/h was 0.88 in silty soil. The construction plan proposed in this paper is helpful for further study of shallow tunnel tunnelling process in silty soil.

Numerical Modeling and Optimizing Construction Schemes for Transition Section Complex Structure of Large Scale Underground Railway Station and Tunnel

2012 ◽  
Vol 256-259 ◽  
pp. 1177-1180
Author(s):  
Rui Lang Cao ◽  
Shao Hui He ◽  
De Lian Gao
Keyword(s):  
Cross Section ◽  
Large Scale ◽  
Variable Cross Section ◽  
Variable Cross ◽  
Construction Process ◽  
Large Span ◽  
Transition Section ◽  
Cell Method ◽  
Tunnel Transition ◽  
Underground Station

Based on the engineering background of New Beijing-Zhangjiakou Inter-city railway Badaling underground station and tunnel transition section construction, the problem of tri-arch and large-span variable single arch construction schemes in the transition section launched research. This paper draws some basis and the law as reference in construction process by the simulate calculation of ABAQUS finite element analysis software. This thesis discuss the frequently-used methods(middle cell method, one-side wall drift heading method, CRD-4 holes method and CRD-6 holes method) that is used in large-scale variable cross-section tunnel engineering research and analysis the stress, deformation and plastic areas distribution of surrounding rock by the simulate calculation of construction process. By comparative analysis, confirm the best construction scheme of transition section: the middle cell method applies to tri-arch cross-section and the CRD-4 holes method applies to large-span single arch of variable cross-section. It can offer direct guidance to the Badaling underground station and tunnel transition section project and some reference to similar underground projects.

Electrical-thermal-mechanical properties of multifunctional OPV-ETFE foils for large-span transparent membrane buildings

2018 ◽  
Vol 66 ◽  
pp. 394-402 ◽  
Author(s):  
Jianhui Hu ◽  
Wujun Chen ◽  
Yue Yin ◽  
Yipo Li ◽  
Deqing Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Large Span ◽  
Thermal Mechanical Properties

scholarly journals On anisotropic mechanical properties of heterogeneous magnetic polymeric composites

2019 ◽  
Vol 377 (2143) ◽  
pp. 20180212 ◽  
Author(s):  
Dmitry Borin ◽  
Gennady Stepanov ◽  
Eike Dohmen
Keyword(s):  
Magnetic Field ◽  
Mechanical Properties ◽  
External Field ◽  
Axial Loading ◽  
Homogeneous Magnetic Field ◽  
Field Application ◽  
Direction Parallel ◽  
Shear Moduli ◽  
Planar Shear ◽  
Anisotropic Mechanical Properties

This study is devoted to the magneto-mechanical characterization of heterogeneous magnetoactive elastomers based on an elastic polydimethylsiloxane matrix with embedded spherical magnetic soft microparticles and magnetic hard microparticles of irregular shape. An issue of the anisotropic mechanical properties of these smart composites is considered. Non-magnetized and pre-magnetized specimens are characterized using a planar shear and axial loading in an externally applied homogeneous magnetic field. The field direction differs relative to the direction of the field used for the specimens pre-magnetization. Results of the different methods allow comparison of the tensile shear moduli for the samples with an initially identical composition. Obtained results demonstrate a strong correlation between the composite behaviour and orientation of the magnetic field used for the pre-magnetization of the sample relative to the external field applied to a sample during the test. Composites pre-magnetized in the direction parallel to an applied mechanical force and external magnetic field show higher magnetorheological response than composites pre-magnetized transversally to the force and the field. Application of the external field directed opposite to the direction of the pre-magnetization reduces the observed stiffening. Moreover, in this situation a softening of the material can be observed, depending on the magnitude of the external field and the field used for pre-magnetization. This article is part of the theme issue ‘Heterogeneous materials: metastable and non-ergodic internal structures’.

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