Dynamic responses of shield tunnel structures with and without secondary lining upon impact by a derailed train

Yan, Qixiang,Li, Binjia,Deng, Zhixin,Li, Bin Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.6

The aim of this study was to investigate the mechanical responses of a high-speed railway shield tunnel subjected to impact by a derailed train, with emphasis on the protective effect of the secondary lining. To do so, the extended finite element method was used to develop two numerical models of a shield tunnel including joints and joint bolts, one with a cast-in-situ concrete secondary lining and one without such a lining. The dynamic responses of these models upon impact were analyzed, with particular focus on the distribution and propagation of cracks in the lining structures and the mechanical responses of the joint bolts. The numerical results showed that placing a secondary lining significantly constricted the development of cracking in the segmental lining upon the impact load caused by a derailed train, reduced the internal forces on the joint bolts, and enhanced the safety of the segmental lining structure. The outcomes of this study can provide a numerical reference for optimizing the design of shield tunnels under accidental impact loading conditions.

Dynamic Characteristics of Intersection Structure Consisting of Twin Shield Tunnels and a Transverse Passage

Qixiang Yan,Junchen Zhang,Wenyu Chen,Longxiang Ma,Cong Wu,Wen Zhang 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.11

The intersection structure, composed of twin shield tunnels and a transverse passage, is ubiquitous in the metros around the world. However, the dynamic characteristics of this kind of intersection structure have not been studied a lot yet. By carrying out the corresponding model tests and numerical simulations, the dynamic characteristics of this kind of intersection structure are studied in this paper, which is very helpful for the determination of the ground vibration from this kind of underground structure. The results show that the vibration of the transverse passage is more severe than the main tunnel, manifested that the frequency response function (FRF) of the transverse passage has greater magnitudes than that of the main tunnel at the locations with the same distance from the vibration source. The peak frequencies of the acceleration responses at different locations of the intersection structure under the moving train load are all located in the frequency band 44.9 − 56.1 Hz where the corresponding 1/3 octave band spectra of FRF have the largest values in the considered frequency band 31.5 − 250 Hz, indicating that the natural frequencies of the intersection structure in the frequency band 44.9~56.1 Hz have significant influences on its acceleration responses below 250 Hz induced by the moving train.

Analysis on the Dynamic Responses of an Overlapped Circular Shield Tunnel under the Different Vibration Loads

Qixiang Yan,Junchen Zhang,Wenyu Chen,Chaofan Yao,Wenbo Yang,Hang Chen,Xirui Liu 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.10

At present, there are many studies on the dynamic response of overlapped tunnels, but most of them are through numerical simulation. Very few has been conducted by the experimental model research and frequency domain analysis. Combined with the model test and the numerical simulation, the dynamic response of the tunnel lining structure under the action of different train speeds and different tunnel clear distances are investigated, which can remedy the deficiencies in the relevant fields and verify the accuracy of numerical simulation results. The results show that as the train speed increases, the amplitude of the energy spectra of the vibration loads decrease significantly. The tunnel response at the sidewalls is smaller than that at the tunnel crown and at the invert in the lower tunnel. As the net distance increases, the amplitudes of the acceleration frequency spectrum and the energy spectra of the lower tunnel decrease, but with a diminishing rate. The dynamic coefficients of circumferential of the upper tunnel under a train load are larger than those in the longitudinal direction in the invert.

Nonlinear Transient Analysis of Temperature Fields in an AGF Project used for a Cross-Passage Tunnel in the Suzhou Metro

Qixiang Yan,Yajun Xu,Wenbo Yang,Ping Geng 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.4

This paper examines the evolution process of the freezing curtain and the transition process of unfrozen water in an ArtificialGround Freezing (AGF) project used for a cross-passage tunnel in the Suzhou Metro, China. The focus of this study was onconfirmation of the rationality of the freezing design on a weak silty clay layer, using a prognosis of the temperature development bynumerical simulation and field monitoring. For the above purposes, basic mathematical techniques were employed to address thenonlinear transient thermal conduction problem considering the release of latent heat. The comparison analysis of the temperaturesgained by field testing versus numerical simulation was performed to verify the accuracy of the numerical model. The resultsindicated that the formation of a stable freezing curtain with the design thickness required more time than the estimated activefreezing period. The variation of unfrozen water volumetric content within the frozen fringe is normally exhibited as a process ofincrease and then decline until it vanishes, whereas there was a gradual and continuous increase near the frozen fringe. Althoughthere was a deviation in the results between field monitoring and the numerical simulation, the general temperature curves from bothmethods were essentially consistent.

Monitoring and Evaluation of Artificial Ground Freezing in Metro Tunnel Construction-A Case Study

Qixiang Yan,Wang Wu,Chuan Zhang,Shuqi Ma,Yuanping Li 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.5

The turn-back tunnel of Guangzhou Metro Line 3 Tianhe Station with a large span was excavated in sandy clay which may easily break and disintegrate. The artificial ground freezing (AGF) technique was used to stabilize the soil and to prevent its collapse during excavations. Most of the existing theoretical analysis and numerical simulation on the AGF technique are purely based on a couple of assumptions, which are not able to produce accurate predictions. It would be more accurate for the AGF analysis to include the field monitoring. In this study, the coupled method of the field monitoring, the analytical formula, and the numerical method is used to evaluate the thickness and average temperature of the frozen zone. Field monitoring was conducted to measure the temperature of the brine and the ground. Analytical formula was used to compute the thickness and the average temperature of the frozen zone. Numerical simulation is also carried out to predict the thickness and the temperature field of the frozen zone. According to the analytical and numerical analysis, the computed thickness and average temperature of the frozen zone meet the designed requirements of the project, which are further confirmed by the successful excavation of the tunnel. This indicates that the coupled method used in this paper is reliable and would be helpful for the AGF application in practical engineering.

Dynamic responses of shield tunnel structures with and without secondary lining upon impact by a derailed train

Qixiang Yan,Binjia Li,Zhixin Deng,Bin Li 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.6

The aim of this study was to investigate the mechanical responses of a high-speed railway shield tunnel subjected to impact by a derailed train, with emphasis on the protective effect of the secondary lining. To do so, the extended finite element method was used to develop two numerical models of a shield tunnel including joints and joint bolts, one with a cast-in-situ concrete secondary lining and one without such a lining. The dynamic responses of these models upon impact were analyzed, with particular focus on the distribution and propagation of cracks in the lining structures and the mechanical responses of the joint bolts. The numerical results showed that placing a secondary lining significantly constricted the development of cracking in the segmental lining upon the impact load caused by a derailed train, reduced the internal forces on the joint bolts, and enhanced the safety of the segmental lining structure. The outcomes of this study can provide a numerical reference for optimizing the design of shield tunnels under accidental impact loading conditions.

Germplasm Resources and Breeding of Primula in China

Zhang Qixiang,Liang Shule,Liu Qingchao,Pan Huitang,Jin Xiaoxia,Zhang Yanli,Zhang Ruili 한국원예학회 2006 한국원예학회 기타간행물 Vol.- No.-