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.

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 Deterioration and Cavity of Surrounding Rocks at the Bottom of Tunnel Under the Combined Action of Heavy-Haul Load and Groundwater: An Experimental Study

2021 ◽  
Vol 9 ◽  
Author(s):  
Zheng Li ◽  
Kunping Chen ◽  
Ziqiang Li ◽  
Weiwei Huang ◽  
Xinsheng Wang
Keyword(s):  
Hydrodynamic Pressure ◽  
Cohesive Soil ◽  
Surrounding Rock ◽  
Structural Defects ◽  
Soil Pressure ◽  
Railway Tunnel ◽  
Heavy Haul ◽  
Combined Action ◽  
Cavity Characteristics ◽  
Heavy Haul Railway

In China, the first tunnel was built in accordance with the 30-ton heavy-haul railway standard. Based on the change in water and soil pressure obtained from long-term on-site monitoring, the cavity mechanism of the surrounding rock at the bottom of a heavy-haul railway tunnel under rich water conditions was explored in this study. The cavity characteristics and degradation depth of the three types of surrounding rock under different axial loads and hydrodynamic pressures were analyzed through laboratory tests. The structural defects at the bottom of the tunnel and local cracks in the surrounding rock were determined to provide a flow channel for groundwater. The dynamic load of heavy-haul trains causes groundwater to exert high hydrodynamic pressure on the fine cracks. The continuous erosion of the bottom surrounding rock leads to a gradual loss of surrounding rock particles, which would further exacerbate with time. The cohesive soil surrounding rock is noticeably affected by the combined action of heavy-haul load and groundwater in the three types of surrounding rock, and the surrounding rock cavity is characterized by overall hanging. In the simulation experiment, the particle loss of the surrounding rock reached 1,445 g, which is 24.2% higher than that of the pebble soil surrounding rock and 40.8% higher than that of sandy soil surrounding rock. The findings of this study could be helpful for developing methods for defect prediction and treatment of heavy-haul railway tunnels.

Experimental research on the dynamic response characteristics of the transition subgrade induced by heavy-haul train passage

2019 ◽  
Vol 233 (9) ◽  
pp. 974-987 ◽  
Author(s):  
Huihao Mei ◽  
Wuming Leng ◽  
Rusong Nie ◽  
Renpan Tu ◽  
Yafeng Li ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Repeated Loading ◽  
Moving Loads ◽  
Response Characteristics ◽  
Heavy Haul Train ◽  
Condition Evaluation ◽  
Heavy Haul ◽  
Variation Characteristics ◽  
Heavy Haul Railway ◽  
Moving Train

The dynamic response of the subgrade under moving train loads provides information on subgrade settlement prediction, condition evaluation, and so forth. This paper presents the field dynamics tests on the transition subgrade in the Shuo-Huang heavy-haul railway in China. The variation characteristics of the peak dynamic displacements along the track and subgrade slope were analyzed, and the random distribution characteristics of the peak dynamic displacements at the subgrade shoulder were studied. The response characteristics of the subgrade during the train passage were investigated, and the attenuation regularities of vibration along the subgrade slope were identified. The results indicated that the action of the train moving loads on the subgrade has obvious periodicity, and two bogies in the adjacent wagons should be considered as one loading unit. The peak dynamic displacements at the subgrade shoulder obey normal distribution under the repeated loading of the loading unit. The subgrade bed is dramatically influenced by the dynamic loadings of the trains, and the moving train loads have little influence on the part below the subgrade bed. The results of the research provide the basis for the evaluation of instantaneous and long-term dynamic stability of the subgrade and offer guidance for simulating train moving loads in the model test and numerical analysis to study the dynamic response of the subgrade.

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