scholarly journals Study on Structural Service Performance of Heavy-Haul Railway Tunnel with Voided Base

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Zhiqiang Zhang ◽  
Bowen Zeng ◽  
Chaolong Dai ◽  
Wanping He
Keyword(s):  
Fatigue Life ◽  
Time History ◽  
Vertical Displacement ◽  
Surrounding Rock ◽  
Dynamic Loads ◽  
Vehicle Body ◽  
Monitoring Point ◽  
Heavy Haul ◽  
Heavy Haul Railway

The structural design of heavy-haul railway tunnels still follows the design method of ordinary railway tunnels. Most of them do not take into account the influence of large axle load of 30 t or more, let alone such problems as void of surrounding rock under long-term dynamic loads. In order to analyze the dynamic response of heavy-haul railway tunnels under long-term reciprocating cyclic dynamic loads, considering the factors such as axle load of vehicle body, unsprung mass, and track irregularity, the vibration load time-history curve of heavy-haul railway trains is determined, the three-dimensional dynamics coupling model of dynamic load-tunnel-surrounding rock is established, and the fatigue life of the structure under different void conditions is analyzed based on the S-N curve of concrete. According to the study, the loading, unloading, and vibration caused by train passing will lead to fluctuations in the vertical displacement response of the monitoring point. The peaks and valleys of the response time-history curve correspond to the effect of the train wheels rolling through. When the void is 6 m wide and 10 cm thick, the vertical displacement of the inverted arch is increased by about 9 times, the peak velocity of the inverted arch is increased by about 3.8 times, and the maximum principal stress is increased by about 47.3%, compared with the condition without void. With the same void thickness, the vertical displacement and velocity curves of the inverted arch vary significantly with the increase of the void width. The width of the base void has a significant effect on the fatigue life of the structure of heavy-haul railway tunnels. Based on the operation requirement of 100-year service life, the ultimate void width is 2 m.

scholarly journals Research on Dynamic Response Characteristics for Basement Structure of Heavy Haul Railway Tunnel with Defects

Mathematics ◽  
2021 ◽  
Vol 9 (22) ◽  
pp. 2893
Author(s):  
Jinfei Chai
Keyword(s):  
Constitutive Model ◽  
Dynamic Response ◽  
Principal Stress ◽  
Surrounding Rock ◽  
Railway Tunnel ◽  
Basement Structure ◽  
Measuring Point ◽  
Heavy Haul ◽  
Damage Constitutive Model ◽  
Heavy Haul Railway

Based on the basic principle of thermodynamics, an elastoplastic damage constitutive model of concrete is constructed in this paper. The model is realized and verified in FLAC3D, which provides a solid foundation for the study of dynamic response and fatigue damage to the base structure of a heavy haul railway tunnel. The dynamic response and damage distribution of the base structure of a heavy-duty railway tunnel with defects were numerically simulated by the concrete elastic-plastic damage constitutive model. Then, by analyzing the response characteristics of the tunnel basement structure under different surrounding rock softening degrees, different foundation suspension range and different foundation structure damage degree are determined. The results show the following: (1) The elastoplastic damage constitutive model of concrete can well describe the stress–strain relationship of materials, especially with the simulation results of post peak softening being in good agreement with the test results, and the simulation effect of the unloading–reloading process of the cyclic loading and unloading test also meet the requirements. (2) The initial stress field and dynamic response of the tunnel basement structure under the action of train vibration load are very different from the ideal state of the structure design when the surrounding rock of the base is softened, the base is suspended, or the basement structure is damaged. With the surrounding rock softening, basement hanging, or basement structure damage developing to a certain extent, the basement structure will be damaged. (3) The horizontal dynamic stress amplitude increases with the increase in the softening degree of the basement surrounding rock. The horizontal dynamic stress of the measuring point increases with the increase in the width of the hanging out area when the hanging out area is located directly below the loading line. When the degree of damage to the basement structure is aggravated, the horizontal dynamic tensile stress of each measuring point gradually decreases. (4) The maximum principal stress increment increases with the increase in the fracture degree of the basement structure, while the minimum principal stress increment decreases with the increase in the fracture degree of the basement structure, but the variation range of the large and minimum principal stress increments is small. The research results have important theoretical and practical significance for further analysis of the damage mechanism and control technology of the foundation structure of a heavy haul railway tunnel with defects.

scholarly journals Fatigue Life Characteristics of Segmental Lining Structure for the Shallow Buried Metro Tunnel under the Dynamic Load of a High-Speed Railway

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Wangping Qian ◽  
Taiyue Qi ◽  
Qing Zhao ◽  
Bingrong Pu ◽  
Jin Zhang ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Fatigue Failure ◽  
Dynamic Load ◽  
High Speed ◽  
Dynamic Loads ◽  
High Speed Railway ◽  
Segmental Lining ◽  
Lining Structure ◽  
Metro Tunnel

Shallow buried shield metro tunnels constructed underneath subgrade project of high-speed railways are becoming increasingly common in China, but the lower metro tunnel bears the fatigue effect of dynamic load induced by the upper high-speed railway, so the long-term durability of segmental lining is a nonnegligible problem. The segmental lining structure of metro tunnel is in a state of static-dynamic loads for a long time, especially when a high-speed railway passes above the metro line, and the long-term durability of segmental lining needs further research. Based on theoretical analysis, the effect of different forms of loads on the fatigue life was analyzed, the change law of the static-dynamic loads on segmental lining was summarized, and the method was put forward to evaluate the fatigue life characteristics of segmental lining. The research results reveal that the additional dynamic load is the fundamental reason for the fatigue failure of the structure, and the existence of static load can cause and accelerate the occurrence of structural fatigue failure simultaneously. The results indicate that the fatigue life decreases gradually with the increase of static-dynamic load. Based on coupling analysis of static-dynamic loads of segmental lining, the fatigue life increases first and then decreases with the increase of buried depth of metro tunnel, and it remains unchanged when the depth exceeds a certain value. According to the actual metro tunnel engineering, by using ABAQUS software, a three-dimensional numerical simulation was carried out to analyze the characteristics of the fatigue life and evolution rules of segmental lining. Based on the modified fatigue life formula and metro service life, the optimization design of the buried depth was carried out to determine the most reasonable range of the buried depth. This study provides a valuable reference for safe operation and long-term durability of metro tunnels under high-speed railways.

Fatigue damage of a heavy-haul railway tunnel invert under a 33-tonne axle cyclic load

2019 ◽  
Vol 234 (5) ◽  
pp. 498-510
Author(s):  
Mingnian Wang ◽  
Yinting Zhao ◽  
Ziqiang Li ◽  
Dagang Liu ◽  
Li Yu
Keyword(s):  
Fatigue Damage ◽  
Cyclic Load ◽  
Large Scale ◽  
Surrounding Rock ◽  
Monitoring Methods ◽  
In Situ Tests ◽  
Railway Tunnel ◽  
Severe Fatigue ◽  
Heavy Haul ◽  
Heavy Haul Railway

The average cyclic load of heavy-haul railway trains is generally larger than that of a conventional mixed passenger and freight railway. This load leads to more severe fatigue damage to structures, including the concrete in a tunnel invert. This study focuses on the fatigue damage of a tunnel invert under a cyclic load of 33 tonnes. The damage classifications for the tunnel inverts are given based on field investigations. With large-scale in-situ tests on the Zhang-Tang Heavy-Haul Railway Tunnel, the pressure–time distributions for the additional dynamic stresses on the surface of the track-bed for various classes of the surrounding rock are proposed. They were subsequently validated against numerical simulation using the ANSYS Workbench module. Fatigue damage of the tunnel invert is demonstrated using both numerical and monitoring methods. It has been observed that the damage to the tunnel invert becomes severe and extensive if the quality of the surrounding rock degrades. Damage zones develop first at the top of the invert and then expand to a deeper position, depending on the rock grade.

scholarly journals Fatigue Performance of Tunnel Invert in Newly Designed Heavy Haul Railway Tunnel

2019 ◽  
Vol 9 (24) ◽  
pp. 5514 ◽  
Author(s):  
Cong Liu ◽  
Limin Peng ◽  
Mingfeng Lei ◽  
Chenghua Shi ◽  
Ning Liu
Keyword(s):  
Numerical Simulation ◽  
Rock Pressure ◽  
Coupling Effect ◽  
Surrounding Rock ◽  
Fatigue Performance ◽  
Railway Tunnel ◽  
Heavy Haul ◽  
Surrounding Rock Pressure ◽  
Bottom Structures ◽  
Heavy Haul Railway

The Haoji railway in China is the longest heavy haul railway in the world, including 235 tunnels located along the 1837 km railway. With the increasing axle load of the new line and the basal deterioration of the existing heavy haul railway in China, studying the fatigue performance of the newly designed tunnel structure is essential. To study the coupling effect of the surrounding rock pressure and 30 t axle load train, in this study, we combined three-dimensional numerical simulation and three-point bending fatigue tests to investigate the fatigue performance of the basal structures. The results of numerical simulation indicate that the center of the inverted arch secondary lining is the position vulnerable to fatigue in the lower tunnel structures; the surrounding rock pressure performance exerts a stronger influence on the stress state of the vulnerable position than the dynamic train loads. The S–N formula obtained from the experiment showed that the fatigue life of tunnel bottom structures decreases with increasing surrounding rock pressure and dynamic load. In typical grade V surrounding rock and 30 t axle loads, fatigue failure will not occur in the newly designed tunnel bottom structures within 100 years if bedrock defects are lacking and pressure of surrounding rock is not excessive.

scholarly journals Investigating the vertical displacement of Duhok embankment Dam: A 31- Years Case Study

2021 ◽  
Vol 9 (ICRIE) ◽  
Author(s):  
Sarmad Abdullah M.Salim ◽  
◽  
Sarhat Mustafa Adam ◽  
Keyword(s):  
Vertical Displacement ◽  
Vertical Movement ◽  
Embankment Dam ◽  
The West ◽  
Monitoring Point ◽  
Downward Displacement ◽  
Vertical Displacements ◽  
The City

The paper studies the long-term settlement behaviour of more than 30-year of the Duhok dam. The dam uses as the major lake for water supply to the city of Duhok and nearby areas. High-precision levelling was used to measure the deformation of the dam to monitor vertical displacements. Five survey campaigns were conducted over 30-year duration: 1988, March 1990, June 1999, March 2017 and February 2019. Analysis of the results found that the highest downward displacement of roughly 20.4 cm was witnessed between 1988 and 2019 for a monitoring point (BM24) located centrally along the bank of the dam. On the other hand, the highest vertical movement of roughly 1.5 cm was estimated between 1990 and 2019 at the monitoring point (BM27) on the west side of the dam. The monitoring point (BM24) had the highest average absolute movement of about 6.0 mm (per year) over the 31 years. Detailed results and analyzes are presented in this article.

scholarly journals Performance Deterioration of Heavy-Haul Railway Bridges under Fatigue Loading Monitored by a Multisensor System

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Zhiwu Yu ◽  
Zhi Shan ◽  
Ju Yuan ◽  
Xiao Li
Keyword(s):  
Fatigue Life ◽  
Fatigue Loading ◽  
Load Level ◽  
Polymer Optical Fiber ◽  
Railway Bridges ◽  
Multisensor System ◽  
Linear Variable Displacement Transducer ◽  
Heavy Haul ◽  
Performance Deterioration ◽  
Heavy Haul Railway

Heavy-haul railway bridges play an increasingly essential role in the transportation in China due to the increasing transport volume. The performance deterioration of the scale models of a typical heavy-haul railway bridge under fatigue loading is monitored in this work, based on a multisensor system including the fiber-reinforced polymer optical fiber Bragg grating and electrical resistance strain gauges, linear variable displacement transducer, and accelerometer. Specifically, by monitoring/observing on the failure mode, fatigue life, load-midspan deflection response, material strain development, and so forth, this work develops an S-N model by comparing the relationship between fatigue life and rebar stress range with that between fatigue life and load level and proposes a damage evolution model considering the coupling of the stiffness degradation and inelastic deformation of specimens. It is found that the fatigue life of specimens is determined by the fatigue life of the rebar at the bottom and it may be lower than 2.0 million cycles with a 30-ton axle weight when environmental factors are taken into account. The predictions of the models agree well with experimental results. Therefore, this work furthers the understanding of the fatigue performance deterioration of the bridges by using a multisensor system.

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