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Liu Z.-R.,Xian University of Architecture and Technology | Cui G.-Q.,Xian University of Architecture and Technology | Wang X.,BGI Engineering Consultants LTD.
International Journal of Geomechanics | Year: 2014

Considering the interaction mechanisms between a subway tunnel's structure and the surrounding soil, a new theoretical method was established to analyze the vibration characteristics of the tunnel structure. The tunnel structure is assumed to be a moderately thick cylindrical shell that was never previously used, and all following researches were done on this basis. To begin, the vibration equation of the tunnel structure was established based on the moderately thick cylindrical shells theory, which takes into account transverse shear deformation. Then, a motion equation was set up for the soil around the tunnel in the framework of Navier's wave theory, applicable to a homogeneous, isotropic, linear elastic medium. Based on said analysis and combined with a wave-propagation approach, the vibration control equation of the tunnel structure was established by considering soil-structure dynamic interaction according to the interface conditions. Using the dispersion characteristic equation, the vibration characteristics of the tunnel structure were analyzed. Through the comparison of the analytical results with those obtained based on thin shell theory or the FEM, the effectiveness of this research was verified. Finally, the influences of tunnel radius, wall thickness, and length on the vibration characteristics of tunnel structure were analyzed. Some important findings are drawn as follows: (1) The natural frequencies of each order, calculated using the method proposed in this paper, are close to the solutions based on FEM, and the relative error is less than 10%; (2) The natural frequencies of the tunnel structure that were calculated based on this theory are lower than those based on the thin shell theory; (3) Additional stiffness is the main influencing factor of the soil medium on the vibration characteristics of tunnel structure; (4) When the lower order is dominating in one-modal analysis, it would produce a larger error if soil-structure interaction is ignored; and (5) The natural frequency of tunnel structure decreases with the increase of tunnel radius, wall thickness, and length. © 2014 American Society of Civil Engineers.

Shen X.,BGI Engineering Consultants LTD. | Cai Z.,Nanjing Hydraulic Research Institute | Cai G.,Nanjing Southeast University
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2016

Continuously deepened applications of the predominantly used new in-situ testing techniques in recent years are reviewed in this paper, which focuses on the techniques of CPTU series and some geophysical methods applied in common civil engineering projects and for meeting the new demands for useful extended geotechnical analyses. It is strongly advocated to develop and use more in-situ tests in engineering practices in the light of providing cost-effective and trustable site investigation and evaluation for solving complicated engineering problems. © 2016, Editorial Office of China Civil Engineering Journal. All right reserved.

Han X.,BGI Engineering Consultants LTD. | Li N.,Xian University of Technology | Standing J.R.,Imperial College London
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2011

The urban deep excavation and subway tunneling work can cause ground movement and the deformation or even damage of the nearby buildings or other structures. However, little research has been reported on the characteristics and mechanism of the building deformation based on the studies on real building behavior, which is very important to establish the efficient structural deformation prediction procedure and damage assessment system. A method to evaluate the building deformation modes, i. e. shearing or bending, is proposed in this paper based on the theoretical analysis using a newly suggested parameter 'bending deformation ratio'. From the observation of the measured data of two real buildings in London applying the method suggested, it is found that these two buildings mainly underwent shearing deformation during tunneling excavation. In the subsequent further analyses, it is concluded that for the general multiple-storey building affected by excavation, it is more likely to experience shearing deformation rather than bending. According to this conclusion, it is suggested to use the shearing stiffness to consider the structural effects in the related analyses, which is different from commonly adopted assumption that building deformation is dominated by bending. Also, the structural stiffness ratio E/G is calculated for the first time, which also adds the knowledge on the real characteristics of building deformation by excavation work in the vicinity.

Wang L.,Water Resources University | Wang L.,BGI Engineering Consultants LTD. | Hu F.,Water Resources University | Yin L.,Xian Geology Investigation Institute | And 2 more authors.
Environmental Earth Sciences | Year: 2013

The Yinchuan plain is located in the arid climate zone of NW China. The western margin of the plain is the Helan mountain connecting a series of normal slip faults. The eastern margin of the plain connects with the Yellow River and adjacents with the Ordos platform. The south of the plain is bordered by the EN fault of the Niushou mountain. The bottom of the plain is the Carboniferous, Permian, or Ordovician rocks. Based on the analysis of groundwater hydrochemical and isotopic indicators, this study aims to identify the groundwater recharge and discharge in the Yinchuan plain, China. The hydrochemical types of the groundwater are HCO3-SO4 in the west, HCO3-Cl in the middle, and Cl-SO4 in the east. The hydrochemical types are HCO3-SO4 in the south, HCO3-Cl and SO4-HCO3 in the middle. The hydrochemical types are complex in the north, mainly SO4-HCO3 and Cl-SO4. Deuterium, 18O, and tritium values of groundwater indicate that groundwater recharge sources include precipitation, bedrock fissure water, and irrigation return water. Groundwater discharges include evaporation, abstraction, and discharge to surface water. According to the EW isotopic profile, the groundwater flow system (GFS) in the Yinchuan plain can be divided into local flow systems (LFS) and regional flow systems (RFS). Groundwater has lower TDS and higher tritium in the southern Yellow River alluvial plain and groundwater age ranges from 6 to 25 years. The range of groundwater renewal rates is from 11 to 15 % a-1. The depth of the water cycle is small, and groundwater circulates fast and has high renewal rates. Groundwater has higher TDS and lower tritium in the northern Yellow River alluvial plain. The range of groundwater age is from 45 to 57 years, and renewal rate is from 6 to 0.1 % a-1. The depth of the water cycle is larger. Groundwater circulates slowly and has low renewal rates. © 2012 Springer-Verlag Berlin Heidelberg.

Hou Z.-S.,Yantai University | Gong Q.-M.,Beijing University of Technology | Jiao W.-G.,BGI Engineering Consultants LTD. | Sun Z.-H.,Yantai University
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

Slabbing is a failure phenomenon that the surrounding rock mass is separated into parallel slabs because of splitting effect in underground excavation. It always occurs in intact or relatively intact, hard, brittle and deep buried surrounding rock mass. The slabs are always arc-shaped in circular tunnels. When an arc-shaped slab experiences a bending deformation, which directs to the external of a tunnel, decreases the radius of the slab and increases its curvature, this kind of bending deformation can be named as concave deformation. In the case of the drainage tunnel excavated by TBM in Jinping II Hydropower Station, the existence of arc-shaped slabs owing to splitting in the circular tunnel is definitely pointed out according to the in-situ characteristics of the surrounding rock mass, and the possibility of the concave deformation of the arc-shaped slab is put forward as well. Then the possibility of the concave deformation is demonstrated by means of mechanical analyses and numerical tests respectively. The demonstration reveals that the occurrence of the concave deformation is dominated by the stress difference between vertical and horizontal geostresses which press the circular tunnel into an approximatively elliptical one. The demonstration of the concave deformation for the arc-shaped slab will play an important role in intensive studies on mechanism of dynamic failure of deep and intact rock mass in circular tunnels.

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