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Zhang D.-H.,Beijing Jiaotong University | Liu S.-H.,Beijing Municipal Engineering Research Institute | Ren S.-Q.,China Railway 20 Bureau Group Corporation
Yantu Lixue/Rock and Soil Mechanics | Year: 2015

According to the characteristic curve of the surrounding rock via support in tunnel structures, the strength and the installation timing of the early supports can significantly influence the deformation and stress distribution of surrounding rock. Consequently, as an important part of the early supports in tunneling, the shotcrete support plays an important role in the deformation and stress distribution of the surrounding rock, depending upon the strength growth and hardening rate of the shotcrete after injection. To explore the effects of the strength growth and hardening rate of shotcrete on its early supporting performance, a series of shotcrete field tests was carried out on the tunneling sites. The variations of the strength and elastic modulus of shotcrete were investigated; and the effects of the hardening rate of shotcrete on its early supporting performance were determined. It is concluded that (1) The strength of the shotcrete develops fast and stably in the beginning; the average compressive strength after 24 hours reaches 6.5 MPa; after 48 hours, it increases up to 11.5 MPa. (2) In the surrounding weak rock, it is important to improve the early strength of shotcrete so that the surrounding rock deformation can be controlled. The greater the early strength of shotcrete, the more effective the early support. (3) The shotcrete hardening rate is an important factor controlling the settlement of the tunnel vault. Compared with slowly hardening shotcrete, the rapidly hardening shotcrete can reduce the settlements at the vault and the arch foot by 10.4% and 17%,respectively, and the horizontal displacement at the sidewall by 30.7%. (4) The effect of the hardening rates on the development of the plastic zone in the surrounding rock is insignificant. (5) The strength hardening process of shotcrete should be properly taken into account, and failure to consider the hardening rate of shotcrete may overestimate the supporting performances of the support and significantly underestimate the deformation of the supporting structure. ©, 2015, Academia Sinica. All right reserved.

Nie J.-G.,Tsinghua University | Wang Y.-H.,Tsinghua University | Cai Q.,Beijing Municipal Engineering Research Institute
Gongcheng Lixue/Engineering Mechanics | Year: 2010

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.

Nie J.-G.,Tsinghua University | Li F.-X.,Tsinghua University | Fan J.-S.,Tsinghua University | Cai Q.,Beijing Municipal Engineering Research Institute
Gongcheng Lixue/Engineering Mechanics | Year: 2011

Shear lag effect has significant effect on stress and deflection of composite beams. According to the elastic analytical model of composite beams, stress and deflection analytical solutions for the cases of simply supported composite beams and cantilever composite beam under uniform distribution load and concentrated load are derived by ignoring slip effect in the interface. By introducing effective flange width and effective sectional rigidity, practical design methods for considering shear lag effect of composite beam are presented, and the results calculated by these methods have good agreement with those obtained from analytical solutions. By comparing different design methods for composite beam considering shear lag effect from different countries, the simple practical design method presented in this research is found to have high accuracy despite of its simplicity.

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 | Year: 2010

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.

Zhao Z.-T.,Beijing MTR Construction Administration Corporation | Liu J.,Beijing University of Civil Engineering and Architecture | Wang T.,Beijing MTR Construction Administration Corporation | Liu J.-Y.,Beijing Municipal Engineering Research Institute
Yantu Lixue/Rock and Soil Mechanics | Year: 2015

A 3D elastoplastic numerical model is developed for the structure-soil layers-pipeline system in the Gongyixiqiao metro station project of Beijing metro line 4, and used to analyze the deformation of pipeline and its surrounding soil, based on the measured displacement data. By combing the field monitoring data, numerical simulations and empirical formulations, the effects of pipeline stiffness on ground deformation are analyzed. It is shown that as the soil-pipe stiffness k is less than 0.18, the differential soil-pipe settlement is less than 5%, and the empirical formulation can be used to calculate the soil settlement at the level of pipeline axis. With the increase of pipeline stiffness, the pipeline can constrain the ground movement more significantly, resulting in a reduction of the growth rate of ground settlement or even a negative growth so that the surface settlement can even exceed the ground settlement. By a fitting analysis of the numerical results, a method is proposed for estimating the maximum pipeline settlement for rigidly jointed pipelines, which is based on the soil-pipe stiffness and tunnel-induced ground surface settlement. The method has been used to calculate an actual project settlement, and the difference between the calculated and measured values is found to be less than 4%, showing the applicability of the proposed method. ©, 2015, Academia Sinica. All right reserved.

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 | Year: 2015

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.

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 | Year: 2013

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.

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 | Year: 2015

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.

Ye Y.,Beijing Municipal Engineering Research Institute
Journal of Railway Engineering Society | Year: 2013

Research purposes: The reliability of the advanced geological forecasting for tunnel construction has puzzled engineering technical personnel all the time, and the accuracies of the forecasting result and the forecasting data are crucial to the tunnel construction. If the problems existed in the current forecasting methods and technologies are realized correctly, it will favour continuous improving the forecasting technical level. This paper discusses the main influence factors on the reliability of the advanced geological forecasting for tunnel construction and points out the problems and limitations existed in the current forecasting methods in the areas of the forecasting method, interpretation, space orientation, wave velocity orientation and survey capacity. Research conclusions: (1) Most of forecasting methods have limitations at present, so it is necessary to correctly understand and analyze the forecasting result. (2) Under the complicated geological condition, the comprehensively advanced geological forecasting should be conducted with many methods to verify and supplement them each other. (3) The forecasting reliability and precision can be enhanced by using the synthesized parameterand and space forecasting theory, method and technology.

Li D.,Beijing Municipal Engineering Research Institute
Advanced Materials Research | Year: 2011

With the modern process of city, subway becomes the best choice of resolving the traffic jamming because it is convenient and effective and well-environmental. As so far, there are three kinds of subway construction methods (shield tunnel, hidden excavated tunnel, pit and cover). Hidden excavated tunnel becomes the only choice in complex conditions because it is suitable. It is inevitable that hidden excavation leads to settlement and influence use of adjacent structure. That is even so when the big span tunnel excavates. This paper analyzes the action mechanism of construction scheme with central boring in controlling settlement according to a case in Beijing. At the same time, it analyzes the value and percent of settlement in each step of center drift method according to monitoring data in site. Finally, center drift method is effective measure to control settlement in big span tunnel and reduces the settlement in 5mm. As a successful case, it may be useful to future similar engineering. © (2011) Trans Tech Publications, Switzerland.

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