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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.
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.
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.
A SECURITY DV-Hop Localization Algorithm Resist Spoofing Attack
Wanli ZHANG,Qixiang SONG 보안공학연구지원센터 2015 International Journal of Security and Its Applicat Vol.9 No.11
In order to reduce the node position error of DV-Hop algorithm in wireless sensor network, the artificial bee colony algorithm is introduced to design the DV-Hop algorithm. A new ABCDV-Hop (Artificial Bee Colony DV-Hop) algorithm is proposed in this paper. Based on the traditional DV-Hop algorithm, by using the minimum hops of nodes and position information of anchor nodes, the average distance per hop is solved by artificial bee colony algorithm to make it more close to the actual value. The simulation results show that compared with the traditional DV-Hop algorithm, the improved algorithm can effectively reduce the positioning error without increasing the node hardware overhead.