Shield Tunnel Structure Modal Analysis with Floating Slab Track on Elastic Foundation

2013 ◽  
Vol 838-841 ◽  
pp. 1393-1398
Author(s):  
Li Kang ◽  
Zhen Yu Lei
Keyword(s):  
Elastic Foundation ◽  
Concrete Slab ◽  
Element Model ◽  
Equivalent Model ◽  
Shield Tunnel ◽  
Subgrade Reaction ◽  
Slab Track ◽  
Reaction Coefficient ◽  
Geological Conditions ◽  
Spring Support

A finite element model (FEM) was proposed to analyze the model of floating slab track (FST) system based on elastic foundation in shield tunnel, and the equivalent model of continuous girder and theory of beam on elastic foundation were considered. Floating concrete slab eigenfrequencies can be calculated under the various combinations of subgrade reaction coefficient, steel spring support stiffness, fastener stiffness and thickness of the floating slab. The results show that geological conditions had certain effects on the eigenfrequencies of FST.

Numerical Analysis of Metro Station Construction by Large-Diameter Shield and Pile-Beam-Arch Method

2011 ◽  
Vol 368-373 ◽  
pp. 2711-2715 ◽  
Author(s):  
De Yun Ding ◽  
Xiu Ren Yang ◽  
Wei Dong Lu ◽  
Wei Ning Liu ◽  
Mei Yan ◽  
...  
Keyword(s):  
Ground Deformation ◽  
Large Diameter ◽  
Element Model ◽  
Construction Method ◽  
Shield Tunnel ◽  
Outer Diameter ◽  
Shield Tunneling ◽  
Metro Station ◽  
Dimensional Finite Element ◽  
New Construction

In more and more complicated urban building environment, a new construction method that metro engineering is constructed by large-diameter shield and shallow mining method can be regarded as a great attempt in China. By taking the Gaojiayuan station of Beijing metro line 14 as an engineering background, the main construction steps for the platform of the metro station built by a large-size shield with an outer diameter of 10 m and the Pile-Beam-Arch (PBA) method are introduced. Based on the soil-structure interaction theory, a two-dimensional finite element model is used to simulate the shield tunneling and the platform construction by the PBA method to enlarge the shield tunnel. The ground deformation and structural stress of the platform are predicted. The numerical results can be regarded as a valuable reference for the application of the new construction method in Beijing metro line 14.

scholarly journals Deformation Law and Control Limit of CRTSIII Slab Track under Subgrade Frost Heave

2021 ◽  
Vol 11 (8) ◽  
pp. 3520
Author(s):  
Xiaopei Cai ◽  
Qian Zhang ◽  
Yanrong Zhang ◽  
Qihao Wang ◽  
Bicheng Luo ◽  
...  
Keyword(s):  
High Speed ◽  
Base Plate ◽  
Element Model ◽  
Middle Part ◽  
Railway Track ◽  
Frost Heave ◽  
Track Structure ◽  
Slab Track ◽  
Plastic Damage ◽  
Track Irregularity

In order to find out the influence of subgrade frost heave on the deformation of track structure and track irregularity of high-speed railways, a nonlinear damage finite element model for China Railway Track System III (CRTSIII) slab track subgrade was established based on the constitutive theory of concrete plastic damage. The analysis of track structure deformation under different subgrade frost heave conditions was focused on, and amplitude the limit of subgrade frost heave was put forward according to the characteristics of interlayer seams. This work is expected to provide guidance for design and construction. Subgrade frost heave was found to cause cosine-type irregularities of rails and the interlayer seams in the track structure, and the displacement in lower foundation mapping to rail surfaces increased. When frost heave occured in the middle part of the track slab, it caused the greatest amount of track irregularity, resulting in a longer and higher seam. Along with the increase in frost heave amplitude, the length of the seam increased linearly whilst its height increased nonlinearly. When the frost heave amplitude reached 35 mm, cracks appeared along the transverse direction of the upper concrete surface on the base plate due to plastic damage; consequently, the base plate started to bend, which reduced interlayer seams. Based on the critical value of track structures’ interlayer seams under different frost heave conditions, four control limits of subgrade frost heave at different levels of frost heave amplitude/wavelength were obtained.

Construction Techniques of Deep Diaphragm Wall in the Yellow River-Crossing Project in South-to-North Water Transfer

2011 ◽  
Vol 250-253 ◽  
pp. 1212-1216
Author(s):  
Da Hu Rui ◽  
Qing Hong Wu ◽  
Zhen Feng Cao ◽  
Yu Xia Zhao ◽  
Guang Fan Li
Keyword(s):  
Yellow River ◽  
Water Transfer ◽  
Diaphragm Wall ◽  
Shield Tunnel ◽  
Medium Sand ◽  
Construction Techniques ◽  
Geological Conditions ◽  
North Bank ◽  
Guide Wall ◽  
North Water

Yellow River-Crossing Project in South-to-North Water Transfer approach through the use of shield tunnel and its north bank departure shaft adopts diaphragm wall as enclosure structure. The depth of continuous wall of its shielding starting shaft is 76.6m, which is the deepest at present in china. The continuous diaphragm wall travels through the layer of silver sand, medium sand and loam from top to bottom, where the geological conditions are poor with large difficulty of construction. This paper sets forth construction of guide wall, reinforcing measures before construction, Trenching process, groove segment connections, innovative technologies of uplifting huge reinforcing cage and so on, which will provide guidance and lessons for the similar project

scholarly journals A Typical Basalt Platform Landslide: Mechanism and Stability Prediction of Xiashan Landslide

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Yongliang Huang ◽  
Zhiwei Sun ◽  
Chunyan Bao ◽  
Man Huang ◽  
Anyuan Li ◽  
...  
Keyword(s):  
Rainfall Intensity ◽  
Influencing Factor ◽  
Heavy Rain ◽  
Element Model ◽  
Maximum Tensile Stress ◽  
Natural State ◽  
Landslide Area ◽  
Rainfall Frequency ◽  
Geological Conditions ◽  
Rainfall Statistics

The Xiashan landslide, which is classified as a typical basalt platform landslide, is the most massive landslide in Zhejiang Province, China. Once sliding occurs, it will pose a severe threat to the life and property of downstream residents and the nearby section of Hangzhou-Taizhou Expressway. On the basis of the geological conditions, present situation, and latest monitoring data of the landslide, this study finds that rainfall is the main influencing factor, and the creep mode is the main prediction mode of its subsequent deformation. The rainfall statistics of the landslide area in the past 30 years show that the rainfall and rainfall frequency in the landslide area display an increasing trend. The probability of heavy rain with rainfall intensity of 100–250 mm/day in the landslide area is very high. On this basis, combined with the numerical analysis method, a finite element model of the slope considering rainfall and groundwater conditions is constructed to analyze the causes and failure mechanism of this landslide comprehensively. Results indicate that the maximum tensile stress at the top of the trailing edge under the natural state is 5.10 MPa, which is very close to the saturated tensile strength of rock mass. Thus, tensile cracks are easily generated and developed, thereby causing the failure mode to be the hydraulic driving type. Also, with the increase in rainfall intensity, the slope plastic strain increases and the slope plastic zone develops and extends until it is completely penetrated. When the rainfall intensity is more than 200 mm/day, the slope safety factor is close to unity, and the slope approaches a failure condition. Therefore, the landslide should be controlled through water treatment and integrated with engineering measures.

scholarly journals On the Finite Element Model of Rotating Functionally Graded Graphene Beams Resting on Elastic Foundation

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Nguyen Van Dung ◽  
Nguyen Chi Tho ◽  
Nguyen Manh Ha ◽  
Vu Trong Hieu
Keyword(s):  
Finite Element ◽  
Free Vibration ◽  
Elastic Foundation ◽  
Mechanical Response ◽  
Shear Deformation Theory ◽  
Free Vibration Analysis ◽  
Element Model ◽  
Functionally Graded ◽  
Mode Shapes ◽  
Engineering Practice

Rotating structures can be easily encountered in engineering practice such as turbines, helicopter propellers, railroad tracks in turning positions, and so on. In such cases, it can be seen as a moving beam that rotates around a fixed axis. These structures commonly operate in hot weather; as a result, the arising temperature significantly changes their mechanical response, so studying the mechanical behavior of these structures in a temperature environment has great implications for design and use in practice. This work is the first exploration using the new shear deformation theory-type hyperbolic sine functions to carry out the free vibration analysis of the rotating functionally graded graphene beam resting on the elastic foundation taking into account the effects of both temperature and the initial geometrical imperfection. Equations for determining the fundamental frequencies as well as the vibration mode shapes of the beam are established, as mentioned, by the finite element method. The beam material is reinforced with graphene platelets (GPLs) with three types of GPL distribution ratios. The numerical results show numerous new points that have not been published before, especially the influence of the rotational speed, temperature, and material distribution on the free vibration response of the structure.

scholarly journals Dynamic Stability Discrimination Method for Concrete Dam under Complex Geological Conditions

2019 ◽  
Vol 2019 ◽  
pp. 1-16
Author(s):  
Liaojun Zhang ◽  
Tianxiao Ma ◽  
Hanyun Zhang ◽  
Dongsheng Chen
Keyword(s):  
Stability Analysis ◽  
Dynamic Stability ◽  
Dynamic Instability ◽  
Limit Equilibrium ◽  
Element Model ◽  
Safety Factors ◽  
Stability Calculation ◽  
Dam Foundation ◽  
Geological Conditions ◽  
Dam Foundations

The instability of dams will bring immeasurable personal and property losses to the downstream, so it has always been a trendy topic worthy of investigation. Currently, the rigid body limit equilibrium method is the most commonly used method for the dynamic stability analysis of dams. However, under the action of earthquakes, the instability of the integral dam-foundation system threatens the safety of the dams and is of great concern. In this paper, a stability analysis method that can reflect the complex geological structural forms of dam foundations is proposed in this paper. The advantages are that this method deals with the difficulty in assuming sliding surfaces and the lack of quantitative criteria for the dynamic instability analysis of dams with complex geological structural forms of dam foundations. In addition, through the method, the sliding channels that may appear in the dam foundations can be automatically searched under random earthquake action, and the safety factors of the dynamic instability of dams be quantitatively obtained. Taking a high RCC gravity dam under construction in China as an example, the proposed method is applied to the three-dimensional finite element model of the dam-foundation system of this dam, and then the dynamic stability calculation is carried out. Through this method, the formation process of the dam foundation’s plastic zone and the failure of sliding channels with different strength reduction coefficients are studied on and analyzed detailedly, and the quantitative acquisition of the safety factors is realized. The results show that the method is reasonable and feasible, and helps provide a new idea and method for the dynamic stability analysis of dams.

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