Time filter

Source Type

Su J.,Beijing Jiaotong University | Zhang D.,Beijing Jiaotong University | Yang G.,Beijing Municipal Engineering Research Institute | Niu X.,Beijing Jiaotong University | Zhao J.,Beijing Jiaotong University
Modern Tunnelling Technology

In response to poor controllability and difficulties with compensating for early settlement by conventional passive protective measures during metro construction beneath existing bridges, an active compensation method for pile foundation settlement of an existing bridge is presented in this paper. The upper and lower structures of the bridge are considered as two separate units-specifically, settlement of the upper part is actively adjusted using the help of an automatic monitoring system to keep it in a safety state by means of determining the rational key technical parameters and applying computer-controlled jacking-up devices. This technique has been successfully applied to the construction of Beijing Metro Line 7 beneath the Shuangjing Bridge. ©, 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved. Source

Nie J.-G.,Tsinghua University | Wang Y.-H.,Tsinghua University | Cai Q.,Beijing Municipal Engineering Research Institute
Gongcheng Lixue/Engineering Mechanics

In order to satisfy the requirements of practice, the floor has to be cast with openings. Thusly, the composite steel-concrete beams with whole openings in concrete slab appear. The problem of lateral stability of composite beams resisted sagging moment exists because of the whole openings. The elastic finite element mode is established to analyze the lateral buckling of the composite steel-concrete beams with whole openings in a concrete slab. Based on FEA analysis, the lateral displacement function and rotation function of a cross section is assumed so as to use Rayleigh-Ritz energy method. The formula to calculate the critical buckling load of composite steel-concrete beams with whole openings in the concrete slab is conducted based on Rayleigh-Ritz energy method. Then the parameter analysis is conducted. At last, the necessity of lateral stability of composite beams with whole openings in the concrete slab is indicated by the calculation example. Source

He M.,Beijing Jiaotong University | He M.,Beijing Municipal Engineering Research Institute | Liu J.,Beijing Municipal Engineering Group Co. | Le G.,Beijing MTR Construction Administration Co. | And 2 more authors.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering

Based on a certain constructing running shield tunnel of Beijing metro side-crossing close to a high-rise building, using the finite element method calculation model and site monitoring method, the foundation characteristics of the high-rise building affected by the constructing shield tunnel are studied. In different construction stages, the variations of the foundation settlement and inclination of the high building are analyzed. The simulation results show that stratum vertical displacement has a sudden change near the high-rise building. Away from the building in an enough distance, the displacement curve becomes flat. From site monitoring results, the high-rise building inclined to the direction away from the tunnel prior to the shield closing to the building, while the building inclined towards the tunnel during shield crossing. The settlements of the monitoring points reach the maximum value when the shield is 10.0 m away from the monitoring surface. However, the settlements declined significantly when the shield is more than 60.0 m from the monitoring surface, and finally becomes stable. The simulation and the site monitoring results agree well. The conclusion would be helpful for the future similar shield tunneling projects. Source

Liu J.,Beijing University of Civil Engineering and Architecture | He M.-D.,Beijing Municipal Engineering Research Institute | Song H.-Y.,Beijing University of Civil Engineering and Architecture
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering

Numerical simulation analysis method is empoyed to study the mechanical behaviors of segments of connecting passage of a shield tunnel. The general construction method and process of the connecting passage are introduced. Through field monitoring analysis and three-dimensional finite element analysis, the force and displacement characteristics of the get the contact channel, segments during construction of the connecting passage and after hole-opening are obtained. The results show that during: construction of the connecting passage and after hole-opening, the horizontal additional displacement of the shield segments is generated, towards the direction of the connecting passage. Owing to the construction of the connecting passage, the original forces of the segments lead to stress redistribution of the Most of the segments at the side openings will produce negative tension forces, and it will seriously affect the safety of the shield tunnel. To this end, temporary support reinforcement measures for the shield tunnel segments are proposed. This study has the reference value for similar projects. Source

Cheng L.,The MCC Group | Zhang P.,The MCC Group | Wang F.,Beijing Municipal Engineering Research Institute
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering

The misconception in soil and rock mechanics, the irrational methods of design and construction for anchored structures in ground exist in China, which frequently lead to accidents such as anchor failure, instability and even collapse of engineering structures. According to geotechnical investigations of typical engineering and engineering accidents, theoretical analysis and experimental studies, some mechanical conceptual problems which significantly affect the stability of ground anchorage were studied. The prestressed anchor has the advantages of providing the active resistance and transferring the tensile stress of structures to the deep stable strata and can be widely used to resist dumping, vertical displacement, shear failure along the foundation base and openings collapse. The section of anchor meeting the requirements of tensile stress, the length of free end of the anchor being long enough and the anchoring formations being able to fully mobilize the ground shear strength are basic elements for raising the tensile bearing capacity of anchors. The pressure-dispersive anchor significantly improve the load transfer effect and the anti-corrosion protection performance and has excellent mechanical and chemical stability. The time delay in anchor installation can be effectively controlled and avoided after excavation in the slopes and openings by timely applying tensile anchors and prefabricated reinforced concrete blocks as the high bearing capacity transfer structures. In order to improve the stability of large openings in high stress and low-strength rock, it is necessary to adopt the low prestressed anchors as the initial support, to strictly control the time delay of the installation of high prestressed anchor, to raise the initial prestressed value in design and to strengthen the control of the interaction between the surrounding rock deformation and anchorage resistance (stiffness). ©, 2015, Academia Sinica. All right reserved. Source

Discover hidden collaborations