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Yu F.,Beijing Jiaotong University | Zhang D.,Beijing Jiaotong University | Mu W.,AVIC Institute of Geotechinical Engineering Co. | Wang J.,Beijing Urban Construction Group Co.
Beijing Jiaotong Daxue Xuebao/Journal of Beijing Jiaotong University | Year: 2015

Nanluoguxiang station in Beijing metro line 6 was constructed by combining the excavation method and the tunneling method. This paper focuses on the risk control of piles at the junction of pits and tunnels with the numerical method. According to the indexes of the lateral displacement and bending moment of the piles, the deformational and mechanical characteristics of the piles in 6 cases are studied. The results show as follows. 1) The coupling effect of the excavation of the pit and tunnel can reduce the security risk of the piles at the junction of the pit and the tunnel partly while the coupling effect can be ignored if the pit is excavated firstly because the excavation effect of the pit is obviously stronger than the tunnel's. 2) The ultimate lateral displacement and bending moment of the piles are similar if the tunnel is excavated firstly or the pit and tunnel are excavated simultaneously, while rational excavation scheme can reduce the piles' failure risk significantly during the excavation. The above mentioned research results, which clarified the security state at the junction of the pit and tunnel in different excavation plans, have important guiding value for similar engineering. © 2015, Journal Northern Jiaotong University. All right reserved. Source


Liao Q.,CAS Institute of Geology and Geophysics | Liao Q.,Beijing Urban Construction Group Co. | Li X.,CAS Institute of Geology and Geophysics | Zhu W.,Northeastern University China | Liu J.,University of Western Australia
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2010

Digital image which describes the material by lattice data provides a good base to build the structure model of rock and soil aggregate(RSA) accurately. Based on the analysis of the digital imaging theory, the color contrast between rock and soil in RSA is analyzed. An auto-generating method of RSA structure model is proposed based on digital image to express spatial structure of RSA directly, quickly and accurately. Firstly, the differences of colors between roils and rock blocks are transferred into digital mode, and each pixel in the image of RSA is described by a digital eigenvalue. Then, the threshold for the digital eigenvalue that can represent rock block pixel is obtained by comparing RGB values or HIS values of RSA images. So each pixel is set different material properties according to the threshold; and the numerical structure of RSA is constructed. Besides, the numerical simulation of the structure model of RSA is carried out. It is shown that the nonuniform of rock distribution of RSA will cause an obvious mechanical structure effect on RSA under uniaxial compression. Source


Ma X.-L.,Beihang University | Liu C.-C.,Beihang University | Liu J.-F.,Beijing Urban Construction Group Co. | Chen F.,Beijing Transportation Research Center | Yu H.-Y.,Beihang University
Jiaotong Yunshu Xitong Gongcheng Yu Xinxi/Journal of Transportation Systems Engineering and Information Technology | Year: 2015

In order to analyze urban bus passengers' travel characteristic, this paper proposes several data mining algorithms for boarding stop inference based on IC card and GPS data. For those buses with GPS devices, a data-fusion method with GPS data is developed to estimate individual passenger's boarding stop. For those buses without GPS devices, an improved Bayesian decision tree algorithm with varying steps is presented to calculate the likelihood of each possible boarding stop. In addition, Markov Chain optimization technique is applied to reduce the computational complexity. Empirical data from Beijing transit route are used to validate the effectiveness of the proposed algorithms. The results demonstrate that the accuracy of identified boarding stop can be guaranteed and the algorithm complexity can be well controlled to meet the requirements of practical application. As a result, the methods can be widely adopted for urban public transportation system. Copyright © 2015 by Science Press. Source


Wu F.,Beijing Urban Construction Exploration and Surveying Design Research Institute Co. | Wu F.,Beijing Urban Construction Group Co. | Wu F.,University of Science and Technology Beijing | Jin H.,Beijing Urban Construction Exploration and Surveying Design Research Institute Co. | Shang Y.,CAS Institute of Geology and Geophysics
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2013

Through summarizing the monitoring results, it is pointed that when the pipeline rigidity is large, and the settlement between pipeline and formation is large. The general deformation law of underground pipeline is basically the same to the move of stratum. When the pipeline is vertical above the tunnel, the settlement curve fits to the normal distribution. The Peck formula for ground surface settlement prediction in tunnel engineering is corrected, and the pipeline settlement prediction formula is established. Combining the former research results of stratum loss rate V1, the reference value of pipeline settlement trough width parameter Kp is calculated. The result of numerical simulation shows that the deformation of pipeline parallel above the tunnel is more than vertical above the tunnel, and the pipeline settlement prediction formula may preliminarily evaluate the deformation of pipeline parallel above the tunnel. The rigid pipeline longitudinal strain calculation formula may also be modified to get the pipeline deformation. The engineering application proves that the pipeline settlement prediction formula, numerical simulation and monitoring results are in good agreement, and the pipeline settlement prediction formula is good in application. Source


Sun Y.,Beijing Jiaotong University | Zhang D.,Beijing Jiaotong University | Yu F.,Beijing Jiaotong University | Wang J.,Beijing Urban Construction Group Co. | Huang J.,Jiangsu Transportation Research Institute
Zhongguo Tiedao Kexue/China Railway Science | Year: 2016

By analyzing the differences in the boundary conditions and balance equations of secondary lining structure and common compressed structure in "Code for Design on Tunnel of Railway", a conclusion can be drawn that using uniaxial tensile and compressive strength as the parameter for estimating the failure of secondary lining material for high speed railway tunnel seems to be excessively safe. Taking a high speed railway tunnel with V-class surrounding rock and for the train speed of 350 km·h-1 as research object, the quasi-stratum-structure model was established by using MIDAS-NX numerical simulation software. The conversion relation between the strength parameter and uniaxial strength of concrete material was derived under the guidance of Mohr-Coulomb strength criterion. On this basis, the deformation characteristics and the ultimate bearing capacity of secondary lining were analyzed and compared with the measured data of second lining structure. The results show that, as the lateral pressure coefficient increases gradually, the tunnel shape turns progressively from flat to upright under critical failure condition. After loading, the plastic zone both inside and outside of the secondary lining structure is obviously influenced by lateral pressure coefficient. The secondary lining structure shows the optimal bearing capacity as the lateral pressure coefficient is 1.4. The steel bars of secondary lining mainly control the first principal stress (tensile stress) of lining element. The actual loading amount of secondary lining is far less than its ultimate bearing capacity. Accordingly, the secondary lining can be "thinned". © 2016, Chinese Academy of Railway Sciences. All right reserved. Source

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