Field investigation and full-scale model testing of mud pumping and its effect on the dynamic properties of the slab track–subgrade interface

2018 ◽  
Vol 233 (8) ◽  
pp. 802-816 ◽  
Author(s):  
Junjie Huang ◽  
Qian Su ◽  
Wei Wang ◽  
Pham Duc Phong ◽  
Kaiwen Liu
Keyword(s):  
Fine Particles ◽  
Dynamic Properties ◽  
Full Scale ◽  
Scale Model ◽  
Track Structure ◽  
Expansion Joints ◽  
Passenger Comfort ◽  
Slab Track ◽  
Concrete Base ◽  
Mud Pumping

Passenger comfort and safety are the most important aspects in the operation of high-speed railways. Mud pumping is a typical problem that occurs in the slab track and the subgrade interface, which influences passenger comfort and safety. In this paper, various field investigations and a full-scale model of the slab track and the subgrade are presented. The external and internal characteristics of mud pumping in the slab track–subgrade interface and the influence of mud pumping on the dynamic properties of the slab track–subgrade are analyzed. The results show that mud pumping only occurs at the expansion joints in the concrete base of the slab track structure. This happens due to the infiltration of rainwater into the subgrade bed through the cracks in the expansion joints. When the upper layer of the subgrade is kept saturated in the full-scale model, mud pumping is found to occur after 3.0 × 104 loading cycles. The vibration ratio of the subgrade surface to the concrete base gradually increases with continued cyclic loading. In addition, the cumulative settlement of the subgrade increased continuously. After 2.0 × 106 loading cycles, it was found that a large volume of slurry composed of water and fine particles was squeezed out of the subgrade bed, and mud pumping occurred on the surface of the subgrade bed leading to the formation of a mud layer between the concrete base and the subgrade bed, causing a loss of contact between the subgrade bed and the concrete base. This reduces the ability of the subgrade bed to support the slab track structure.

scholarly journals Vibration Behavior and Reinforcement Effect Analysis of the Slab Track-Subgrade with Mud Pumping under Cyclic Dynamic Loading: Full-Scale Model Tests

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Junjie Huang ◽  
Qian Su ◽  
Wei Wang ◽  
Xun Wang ◽  
Huiqin Guo
Keyword(s):  
Epoxy Resin ◽  
Normal Condition ◽  
Full Scale ◽  
Scale Model ◽  
Reinforcement Effect ◽  
Slab Track ◽  
Vibration Behavior ◽  
Low Viscosity ◽  
Concrete Base ◽  
Mud Pumping

Mud pumping occurring in the subgrade bed can gradually deteriorate the performance of the slab track-subgrade, negatively affecting the comfort and safety of high-speed railway. In this paper, a full-scale model of the slab track-subgrade was established to analyze the vibration behavior of the model in normal condition and before and after mud pumping reinforced, as well as the reinforcement effect of mud pumping using low-viscosity epoxy resin. The research results show that the vibration acceleration and displacement and the settlement of the model in normal condition stabilize gradually with the increasing number of loading cycles. Under the upper layer of the subgrade bed saturated by water, mud pumping occurs in the subgrade bed as soon as the second loading stage reaches to 3.0 × 104 cycles, and the deterioration of mud pumping increases gradually with the increasing number of loading cycles. Moreover, a large volume of slurry composed of water and fine particles is squeezed out of the subgrade bed after the model is subjected to the second cyclic loading stage of 2.0 × 106 cycles, causing contact loss between the concrete base and the subgrade bed, which makes the acceleration and displacement of the concrete base increase abnormally compared with the model in normal condition, as well as the cumulative settlement of the subgrade bed. The model with significant mud pumping in the upper layer of the subgrade bed was reinforced by using low-viscosity epoxy resin. This effectively controlled the abnormal acceleration and displacement of the concrete base and restored the support capability of the subgrade bed for the concrete base of the slab track structure.

Full scale model tests on slab track constructed on embankment

2012 ◽  
pp. 547-553 ◽  
Author(s):  
Jiang Hongguang ◽  
Bian Xuecheng ◽  
Chen Yunmin ◽  
Jiang Jianqun
Keyword(s):  
Model Tests ◽  
Full Scale ◽  
Scale Model ◽  
Slab Track

scholarly journals Experimental study on mechanical properties of heavy-haul low-vibration track under train static load

2020 ◽  
Vol 103 (2) ◽  
pp. 003685042092724
Author(s):  
Wuji Guo ◽  
Zhiping Zeng ◽  
Shiye Li ◽  
Weidong Wang ◽  
Abdulmumin Ahmed Shuaibu ◽  
...  
Keyword(s):  
Working Conditions ◽  
Static Load ◽  
Development Trend ◽  
Full Scale ◽  
Scale Model ◽  
Track Structure ◽  
Vertical Load ◽  
Wheel Load ◽  
Heavy Haul ◽  
Track Slab

In this paper, a full-scale model of Low Vibration Track was established and three working conditions were applied to a single bearing block; these include: vertical load at the end of the track slab, combination of horizontal and vertical load at the end of the track slab, and vertical load at the middle of the track slab. By applying four times static wheel load to the full-scale model, the relationship between the stress of the track structure and the load under different working conditions was investigated. The corresponding load values were obtained when the track slab and the bearing block reached the axial tensile strength of the concrete. Through the static load test, the weak position of the track structure was found, and the development trend of the crack was obtained. (1) Obtained the maximum stress of the concrete of the track slab at the corner of the bearing block, the maximal stress of the concrete of the track slab, the stress at the bottom of the bearing block, and the stress at the bottom of the bearing block under different working conditions. (2) The horizontal load of the train increased the force of the track slab concrete at the corners of the bearing block. (3) Compared the strain of different location of the track slab and different working conditions. (4) Observed the positions of slight crack and its development trend appeared on track slabs in different working conditions. (5) For the weak part of the track structure, it can be improved by measures such as increasing the thickness of the end of the track slab and arranging stirrups in the track slab around the support block. The research results provide reference for the design, application and maintenance of Low Vibration Track in the heavy-haul railway tunnel.

scholarly journals Study on the Mechanical Characteristics of the Sleeper Slab Track on a Long-Span Steel Truss Bridge

2021 ◽  
Vol 11 (11) ◽  
pp. 5273
Author(s):  
Zhiping Zeng ◽  
Xiangdong Huang ◽  
Weidong Wang ◽  
Bin Zhu ◽  
Zheng Zhang ◽  
...  
Keyword(s):  
Resistance Test ◽  
Scale Model ◽  
Track Structure ◽  
Loading Test ◽  
Slab Track ◽  
Long Span ◽  
Steel Truss Bridge ◽  
Steel Truss ◽  
Static Loading Test ◽  
Truss Bridge

This paper uses the long-span steel truss slab track as its research subject to analyze the new type of sleeper slab track structure with an experimental method. Firstly, a full-scale model was established in the laboratory to form a “rail–sleeper slab–self-compacting concrete cushion–steel beam” composite structure, and a fatigue test was performed on the track structure. The cyclic load was set up as a sine form with a range between 75 and 375 kN at a 5 Hz interval and 3 × 106 cycles. Based on the test, the performance of the track structure under cyclic train load was studied. Secondly, after every 106 loading cycles, the vertical static loading test and horizontal resistance test of the track structure were carried out to obtain the strain and displacement under different loading cycles. Finally, after 3 × 106 cycles of sine cyclic loading, the horizontal ultimate resistance test of the track structure was carried out to study its horizontal failure mode. The aims of this paper were to verify the applicability of the sleeper slab track, identify the mechanical properties, and determine the unfavorable position. The findings can provide an important reference for the practical use of the sleeper slab track structure.

Full-Scale Model Testing on Ballasted High-Speed Railway: Dynamic Responses and Accumulated Settlements

2018 ◽  
Vol 2672 (10) ◽  
pp. 125-135 ◽  
Author(s):  
Wei Li ◽  
Xuecheng Bian ◽  
Xiang Duan ◽  
Erol Tutumluer
Keyword(s):  
High Speed ◽  
Stable State ◽  
Model Testing ◽  
Full Scale ◽  
Dynamic Responses ◽  
Scale Model ◽  
Vibration Velocity ◽  
Track Structure ◽  
High Speed Railway ◽  
Soil Stress

High-speed trains generate much higher vibrations in track structures than conventional trains and intensive train passages (e.g., on the Beijing–Shanghai high-speed railway line where the train passage interval is less than 5 minutes) cause accumulated permanent settlement in the railway track substructures, which will decrease track performance and jeopardize the safety of trains. Since very few field measurements on ballasted high-speed railways are available in literature, this paper presents experimental results of vibration velocity, dynamic soil stress, and the accumulated settlement of a ballasted high-speed railway from a full-scale model testing facility with simulated trains moving loads at various speeds. A portion of a realistic ballasted railway consisting of track structure, ballast layer, subballast, embankment, and piled foundation was constructed in a larger box. An eight-actuator sequential loading system was used to generate equivalent vertical loadings on the track structure for simulating the dynamic excitations due to train movements. Dynamic stresses measured in the track substructure layers (ballast, subballast, and embankment) were found to be strongly dependent on train speeds especially for speeds higher than 144 km/h. It was found that both the vibration velocity and the dynamic soil stress were greatly amplified as the train speed increased to 300 km/h, and the ballast layer effectively reduced the vibrations transmitted from the track structure to underlying soil. The accumulated settlement of the substructure did not reach a stable state even after 100,000 moving train loads at a speed of 300 km/h.

Effect of mesh on CFD aerodynamic performances of a container ship

2020 ◽  
Vol 20 (3) ◽  
pp. 343-353
Author(s):  
Ngo Van He ◽  
Le Thi Thai
Keyword(s):  
Water Surface ◽  
Reference Model ◽  
Full Scale ◽  
Scale Model ◽  
Container Ship ◽  
Ansys Fluent ◽  
Remarkable Effect ◽  
Aerodynamic Performances ◽  
Mesh Convergence

In this paper, a commercial CFD code, ANSYS-Fluent has been used to investigate the effect of mesh number generated in the computed domain on the CFD aerodynamic performances of a container ship. A full-scale model of the 1200TEU container ship has been chosen as a reference model in the computation. Five different mesh numbers for the same dimension domain have been used and the CFD aerodynamic performances of the above water surface hull of the ship have been shown. The obtained CFD results show a remarkable effect of mesh number on aerodynamic performances of the ship and the mesh convergence has been found. The study is an evidence to prove that the mesh number has affected the CFD results in general and the accuracy of the CFD aerodynamic performances in particular.

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