Hua F.-C.,Beijing Jiaotong University |
Hua F.-C.,Beijing Urban Engineering Design and Research Institute Co.
Yantu Lixue/Rock and Soil Mechanics | Year: 2013
Firstly, based on considering the theoretical solution of liner and grouting circle, the calculation and automatic drawing program has been developed with MATLAB software; and the relationships among water inflow, external water pressure and water head, tunnel radius, rock permeability, lining permeability are researched. Secondly, through the comparison of the numerical result and theoretical solution based on the FLAC3D, the correctness of application of numerical simulation methods to the tunnel seepage field are verified. On this basis, combined with the typical range of Qingdao metro, the seepage fields in the excavation stage and operation period are studied; and the relationships between water inflow and external water pressure of grouting circle are researched under different grouting circle thickness and grouting parameters. The results show that the application of grouting circle to the tunnel to reduce the water inflow is feasible; and the greater the grouting circle thickness and the smaller the grouting circle permeability, the less the tunnel water inflow; but the changing law of the external water pressure is on the contrary. The obtained results play an important role in designing the liner and the preliminary definition of the grouting thickness.
Zhang G.,Tsinghua University |
Rong B.,Beijing Urban Engineering Design and Research Institute Co. |
Fu P.,China Institute of Water Resources and Hydropower Research
Journal of Testing and Evaluation | Year: 2013
The use of large-diameter piles as foundations for offshore wind-driven generators has become increasingly common in recent years. These piles are usually located in saturated soft clay and experience a wide variety of static and dynamic loads. A new approach was described to simulate different types of loads on a large-diameter pile under high g levels in centrifuge model tests by simplifying the complex horizontal load combinations to which such a pile is typically subjected. A series of centrifuge model tests was conducted to assess the influence of several factors. An image-based measurement system, together with a transducer-based measurement, was used to obtain a comprehensive understanding of the response of the soil. The horizontal load-induced bending moment of the pile exhibited a nearly triangular distribution. A critical load, which can be estimated as approximately half of the ultimate load, was found to exist, beyond which the rate of displacement of the pile increased significantly with increasing load. The pile-induced deformation of the soil, concentrated within zones on both sides of the pile, gradually increased as the load increased and became nearly constant when the load was close to the ultimate load. Significant separation occurred between the pile and the neighboring soil in the upper part of the pile. The critical and ultimate loads of the pile were significantly dependent on the behavior of the soil in the upper layer, the depth, and the diameter of the pile. Copyright © 2013 by ASTM International all rights reserved.
Hu S.-M.,Beijing Urban Engineering Design and Research Institute Co.
Tiedao Xuebao/Journal of the China Railway Society | Year: 2014
Taking the large-section loess tunnel project of the Lanzhou-Chongqing Railway as the background, the pressure-arch effect of loess surrounding rock was analyzed by model tests and finite element numerical calculations. The results show as follows: (1) Due to deflection of the load transfer path , the tangential stresses of the portion of the pressure arch ring bear radial loads and so increase; the closer to the tunnel boundary , the greater the increasing magnitude of the tangential stresses, and the pressure arch boundary develops to deep surrounding rock. (2) Keeping to the stress paths in side walls at the tunnel ring, the tangential stresses and radial stresses are lower than the original rock stresses, the tangential stresses show strong stress concentration and the radial stresses increase slightly. (3) Compared with clay soil, the shear strength of loess soil is relatively small, thus requiring a wider range of soil body to bear surrounding rock pressures and causing the outside boundary of the pressure arch to get far away from the tunnel section; referring to the loess surrounding rock pressure arches, the pressures are the largest at side walls and the smallest at arch bottoms and lie in between at arch tops. (4) The fracturing process of loess surrounding rock: undergoes four stages, i.e., generation of local fractures, expansion of local fractures, rapid through fracturing and retention of generation of residual strengths; vault loosening and collapsing occur upon side wall shear slide. (5) Numerical calculations and model tests yield the basically identical ranges of loess surrounding rock pressure arch, thus proving the existence of the pressure arch; the pressure arch bears its self weight as well as the external soil loads over the areas of loosening, pressure-arch and initial stressing from the tunnel ring to deep surrounding rock.
Yong-Chul K.,Dongyang Structure Engineering Co. |
Xue S.,Beijing University of Technology |
Zhuang P.,Beijing University of Civil Engineering and Architecture |
Zhao W.,Beijing Urban Engineering Design and Research Institute Co. |
Li C.,Beijing University of Technology
Earthquake Engineering and Engineering Vibration | Year: 2010
A theoretical model of a friction pendulum system (FPS) is introduced to examine its application for the seismic isolation of spatial lattice shell structures. An equation of motion of the lattice shell with FPS bearings is developed. Then, seismic isolation studies are performed for both double-layer and single-layer lattice shell structures under different seismic input and design parameters of the FPS. The influence of frictional coefficients and radius of the FPS on seismic performance are discussed. Based on the study, some suggestions for seismic isolation design of lattice shells with FPS bearings are given and conclusions are made which could be helpful in the application of FPS. © 2010 Institute of Engineering Mechanics, China Earthquake Administration and Springer Berlin Heidelberg.
Hu S.,Beijing Urban Engineering Design and Research Institute Co.
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2013
For the loess tunnel in Lanzhou-Chongqing high-speed railway, the spatial deformation characteristics of surrounding rock is studied based on the loess engineering properties. The results show that: (1) The engineering properties of loess are characterized by its structure and well developed vertical joints, and structural loess may be modeled by the Mohr-Coulomb criterion with the bilinear failure envelope; (2) The well developed vertical joints may be caused by a large quantity of pore structure and small tensile strength; (3) The vertical displacement of the crown attenuates slowly, while the horizontal displacement of the side wall attenuates rapidly. The integrity of surrounding rock may be impaired due to the vertical joints, the deformation of surrounding rock caused by the excavation disturbance is gradually transferred to the deep; (4) In view of the engineering properties of loess, the plastic zone caused by excavation disturbance increases quickly and leads to tension damage in a wide range; (5) Compared to the existing theories, the computational model may fully consider the engineering properties. Due to the widespread vertical joints, the extrusion deformation at tunnel face induced by tunnel excavation is large, and hence the simulated results accord with the practical surrounding rock in loess.