scholarly journals Study on the Face Stability of a Metro Tunnel in a Silty Clay Layer Constructed Using the Full-Face Method

Symmetry ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1069
Author(s):  
Zhien Zhang ◽  
Mingli Huang ◽  
Chunbo Yu ◽  
Xiaojian Fu
Keyword(s):  
Soft Soil ◽  
Horizontal Displacement ◽  
Silty Clay ◽  
Subway Tunnel ◽  
Tunnel Face ◽  
The Core ◽  
Cut Method ◽  
The Face ◽  
Full Face ◽  
Subway Tunnels

The horizontal displacement of the soil at the face of the subway tunnel is symmetrically distributed along the central axis of the tunnel, which is larger in the middle and smaller at both sides. The displacement is related to the size of the excavation face. If the excavation area is too great, the horizontal displacement of the tunnel face will be too large, easily leading to tunnel face collapse. For this reason, tunnel builders often use the core-keeping ring-cut method to build subway tunnels. A large section is divided into several small sections to reduce the soil displacement caused by soil excavation. With the continuous promotion and application of mechanized construction in the field of tunnels, mechanized full-section construction will gradually be performed in urban subway tunnels. Once the change in construction method from the core-keeping ring-cut method to the full-face method is made, the issue of how to maintain the stability of the tunnel working face (especially the soft soil stratum) becomes the focus of attention. Taking silty clay as the research object, this paper studies the displacement law of core soil with regard to the tunnel face under the condition of full-face excavation by using theoretical analysis, numerical simulations, and outdoor tests. According to the research results, the extrusion displacement of the tunnel face is the main cause of tunnel displacement. We optimize the construction parameters of glass fiber anchors to strengthen the tunnel face and provide theoretical guidance for the safe construction of subway tunnels.

Study of Reinforcement Scheme for Tunnel Heaving due to Excavation of Sunken Plaza over Subway Tunnels

2014 ◽  
Vol 919-921 ◽  
pp. 751-757
Author(s):  
Hong Lin ◽  
Jiang Yang ◽  
Jing Tao Chen ◽  
Qing Quan Luo
Keyword(s):  
Horizontal Displacement ◽  
Radius Of Curvature ◽  
Subway Tunnel ◽  
Large Area ◽  
Reinforcement Scheme ◽  
Soil Cement ◽  
Construction Organization ◽  
Reinforcement Measures ◽  
Subway Tunnels ◽  
Uplift Pile

The excavation of large area close to the top of the tunnel, is likely to lead to a big displacement and deformation of the tunnel, even endanger the safety of subways operation. Therefore, it has become a problem urgently to be solved that how to accurately predict and reduce the deformation of subway tunnel caused by excavation of sunken plaza. Build a numerical model in the finite difference software FLAC 3D, then according to the order of the construction organization, calculation and analysis four different reinforcement schemes in the process of the excavation of sunken plaza, the reinforcement schemes are Without reinforcement measures, adopt gantry soil-cement mixing pile reinforcement scheme, sinking square are at the bottom of the uplift pile reinforcement scheme and comprehensive use of soil-cement mixing pile of door and sinking square with uplift pile reinforcement scheme, then comparison and evaluation the effects of the four kinds of reinforcement schemes around the selected four indicators, they are the maximum vertical settlement of the tunnel, the maximum horizontal displacement value of the tunnel, the maximum convergence of a tunnel diameter and the minimum radius of curvature tunnel deformation curve .From the analysis, some conclusions can be drawn.

scholarly journals Method of Calculating the Compensation for Rectifying the Horizontal Displacement of Existing Tunnels by Grouting

2020 ◽  
Vol 11 (1) ◽  
pp. 40
Author(s):  
Yongjie Qi ◽  
Gang Wei ◽  
Feifan Feng ◽  
Jiaxuan Zhu
Keyword(s):  
Volume Expansion ◽  
Soil Layer ◽  
Horizontal Displacement ◽  
Soil Mass ◽  
Calculation Model ◽  
Additional Stress ◽  
Corrective Effect ◽  
Engineering Data ◽  
Subway Tunnels ◽  
Good Agreement

Sleeve valve pipe grouting, an effective method for reinforcing soil layers, is often employed to correct the deformation of subway tunnels. In order to study the effect of grouting on rectifying the displacement of existing tunnels, this paper proposes a mechanical model of the volume expansion of sleeve valve pipe grouting taking into consideration the volume expansion of the grouted soil mass. A formula for the additional stress on the soil layer caused by grouting was derived based on the principle of the mirror method. In addition, a formula for the horizontal displacement of a tunnel caused by grouting was developed through a calculation model of shearing dislocation and rigid body rotation. The results of the calculation method proposed herein were in good agreement with actual engineering data. In summary, enlarging the grouting volume within a reasonable range can effectively enhance the grouting corrective effect. Further, with an increase in the grouting distance, the influence of grouting gradually lessens. At a constant grouting length, setting the bottom of the grouting section at the same depth as the lower end of the tunnel can maximize the grouting corrective effect.

Material Selection for CFRP-Aluminium-Foam-Sandwiches Manufactured by a PUR Spraying Process

2017 ◽  
Vol 742 ◽  
pp. 317-324
Author(s):  
Peter Rupp ◽  
Peter Elsner ◽  
Kay André Weidenmann
Keyword(s):  
Manufacturing Process ◽  
Sandwich Structures ◽  
Bending Stiffness ◽  
Effective Density ◽  
Sandwich Composites ◽  
Open Cell ◽  
The Core ◽  
Bending Modulus ◽  
The Face ◽  
Spraying Process

Sandwich structures are ideal for planar parts which require a high bending stiffness ata low weight. Usually, sandwich structures are manufactured using a joining step, connecting theface sheets with the core. The PUR spraying process allows to include the infiltration of the facesheet fibres, the curing of the matrix and the joining of the face sheets to the core within one processstep. Furthermore, this manufacturing process allows for the use of open cell core structures withoutinfiltrating the core, which enables a comparison of different material configurations, assembled bythe same manufacturing process. The selection of these materials, with the aim of the lowest possiblemass of the sandwich composite at a constant bending stiffness, is displayed systematically within thiswork.It could be shown that the bending modulus calculated from the component properties matched theexperimentally achieved values well, with only few exceptions. The optimum of the bending modulus,the face sheet thickness and the resulting effective density could be calculated and also matched theexperimental values well. The mass-specific bending stiffness of the sandwich composites with corestructures of open cell aluminium foams was higher than with closed cell aluminium foams, but wasexceeded by sandwich composites with Nomex honeycomb cores.

Prediction of long-term settlements of subway tunnel in the soft soil area

2014 ◽  
Vol 74 (2) ◽  
pp. 1007-1020 ◽  
Author(s):  
Zhen-Dong Cui ◽  
Shi-Xi Ren
Keyword(s):  
Soft Soil ◽  
Subway Tunnel ◽  
Soft Soil Area ◽  
Soil Area

Devolution processes and the theory of historical development by S. Sanderson

2021 ◽  
pp. 72-77
Author(s):  
A.V. Verkhoturov ◽  
◽  
A.A. Obukhov
Keyword(s):  
Historical Development ◽  
World System ◽  
Human Society ◽  
Evolutionary Trend ◽  
The Core ◽  
The World ◽  
The Face ◽  
American Historian ◽  
Immanuel Wallerstein ◽  
Main Ideas

Analyzed is one of the most comprehensive modern approaches to the problem of the existence of evolution of human society as such and of specific human communities, i.e. “General Theory of Historical Development” by American historian and sociologist Stephen Sanderson. While agreeing, in general, with its main ideas, we believe that it is important to note that the issue of existence of individual communities demonstrating devolution (regression to an earlier historical state), stagnation or degeneration at certain historical stages is practically ignored in the framework of the theory under consideration. This creates its vulnerability in the face of specific empirical data, indicating a deviation from the evolutionary trend. We believe that overcoming this theoretical difficulty is possible in the process of comprehending the theory of S. Sanderson in the context of ideas of the world-system approach of Immanuel Wallerstein. We want to show that examples of devolution, stagnation and degeneration of societies do not deny general progressive evolutionary tendencies, characteristic for the world-system as a whole, but only indicate the transition of a particular society to a lower level within the world-system (from the core to the semi-periphery, or from the semi-periphery to the periphery).

scholarly journals The Influence of the Track Parameters on Vibration Characteristics of Subway Tunnel

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Wenbo Shi ◽  
Linchang Miao ◽  
Junhui Luo ◽  
Honglei Zhang
Keyword(s):  
Soft Soil ◽  
Power Level ◽  
Coupling Model ◽  
Calculation Model ◽  
Vertical Acceleration ◽  
Subway Tunnel ◽  
Ballastless Track ◽  
Train Operation ◽  
The Impact ◽  
Wheel Track

In soft soil areas, such as the Nanjing, it is very important to quantitatively analyze the dynamic behaviors of soft soils during the metro train operation. A nonlinear coupling model of wheel-track and a finite element calculation model of tunnel and soil were established based on the mechanical character of elastic supporting block ballastless track and the actual parameters of Nanjing soft soil. The time-variant vertical acceleration of the rail, the sleepers, and the surface of the tunnel can be calculated by the models, and the frequency dependence acceleration was verified by the fast Fourier transform algorithm. A modified vibration power level for human sensitivity was used to quantify the vibration energy of each part of the system, and the impact of the parameters in the model was evaluated. The results can be applied to the metro design and construction, which also can be the guidance during the tunnel construction.

A Veiled Threat: Belcacemi and Oussar v Belgium

2018 ◽  
Vol 20 (2) ◽  
pp. 190-200
Author(s):  
Jasper Doomen
Keyword(s):  
Criminal Law ◽  
Freedom Of Conscience ◽  
Unequal Treatment ◽  
The Face ◽  
The Individual ◽  
Full Face ◽  
The Right

The freedom of the individual can easily come into conflict with his or her obligation to integrate in society. The case of Belcacemi and Oussar v Belgium provides a good example. It is evident that some restrictions of citizens’ freedoms must be accepted for a state to function and, more basically, persist; as a consequence, it is acceptable that certain demands, incorporated in criminal law, are made of citizens. The issue of the extent to which such restrictions are justified has increasingly become a topic of discussion. The present case raises a number of important questions with respect to the right to wear a full-face veil in public if the societal norm is that the face should be visible, the most salient of which are whether women should be ‘protected’ from unequal treatment against their will and to what extent society may impose values on the individual. I will argue that Belgian law places unwarranted restrictions on citizens and that the values behind it testify to an outlook that is difficult to reconcile with the freedom of conscience and religion.

scholarly journals CONCERNING THE EXTRACTION OF A SLACK SOIL LAYER FROM COMPRESSIBLE THICKNESS OF FOUNDATION STRATUM OF FINITE WIDTH FOUNDATIONS

2019 ◽  
Vol 7 (4) ◽  
pp. 49-56
Author(s):  
Zaven Ter-Martirosyan ◽  
Armen Ter-martirosyan ◽  
Valery DEMYANENKO
Keyword(s):  
Analytical Solutions ◽  
Soft Soil ◽  
Soil Layer ◽  
Horizontal Displacement ◽  
Creep Model ◽  
Shear Stresses ◽  
Finite Width ◽  
Relative Depth ◽  
Weak Layer ◽  
Horizontal Displacements

The paper provides a quantitative assessment of the deflected mode of foundation stratum of finite width foundation, in the compressible thickness of which there is a slack clay soil layer. A number of criteria for assessing the possibility or impossibility of extruding a slack layer depending on its strength and rheological properties, as well as the relative thickness of the layer to its length (h/l) and the relative depth of the layer (h/d) have been given. Closed analytical solutions are given to determine the rate of Foundation precipitation depending on the rate of extrusion of the weak layer, including taking into account the damped and undamped creep. The analytical solutions in the article are supported by the graphical part made with the help of the Mathcad program. Plots of changes in shear stresses in the layer along the x axis at different distances from the axis and at different values 0, contours of horizontal displacement velocities in the weak layer at different distances from the x axis, plots of horizontal displacement velocities in the middle of the weak layer and plots of horizontal displacement velocities in the weak layer at different distances from the x axis are given. As a calculation model for describing the creep of a slack layer, rheological ones of the soil using power and hyperbolic functions and their modifications have been considered. In addition, most modern rheological models that take into account soil hardening during creep have been considered. Based on these models, the problem is solved by means analytical and numerical methods using the Mathcad PC and the PLAXIS PC according to the Soft Soil Creep model. The graphical part shows the isofields of horizontal displacements for 300 days and 600 days and the corresponding contours of horizontal displacements.

scholarly journals Study on construction risk and control technology of subway tunnel in soft soil stratum

2021 ◽  
Vol 634 (1) ◽  
pp. 012116
Author(s):  
Heng Kong ◽  
Fei Guo ◽  
Mi Zhang ◽  
Shenglei Gao ◽  
Kaili Wang
Keyword(s):  
Soft Soil ◽  
Control Technology ◽  
Subway Tunnel ◽  
Soil Stratum ◽  
Construction Risk ◽  
And Control

scholarly journals Analysis of Ground Deformation Caused by Subway Tunnel Excavation in Kunming

2021 ◽  
Vol 236 ◽  
pp. 03029
Author(s):  
Ping Wei ◽  
Liuchuang Wei
Keyword(s):  
Ground Deformation ◽  
Horizontal Displacement ◽  
Subway Tunnel ◽  
Buried Pipelines ◽  
Tunnel Excavation ◽  
Protection Measures ◽  
Geological Conditions ◽  
Soil Stress ◽  
Foundation Deformation ◽  
At Home

Research at home and abroad shows that subway excavation often causes soil stress loss, resulting in settlement deformation and horizontal displacement of stratum. Therefore, combined with the special engineering geological conditions in Kunming area, the foundation deformation caused by subway excavation is studied, so as to provide an important foundation for proposing the protection measures of surrounding buildings and buried pipelines and promoting the construction of subway.

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