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2014 Vol. 31, No. 9
Published: 2014-09-15
Orignal Article
Orignal Article
1
Research on the Management Innovation and Practice of Construction for Beijing-Shanghai High Speed Railway
LU Chun-fang
Construction of Beijing-Shanghai high speed railway is unprecedented great feat.Around the construction goal of "world class",a series innovation and practice measures are taken in the construction ideas, organization and management, technology research, investment financing, quality, safety, investment, construction period, environmental protection, stability, and so on,to lay a solid foundation of completing Beijing-Shanghai high speed railway construction efficiently.In the current new situation of speeding up railway construction, systematically summarizing the results of management innovation and practice for Beijing-Shanghai high speed railway has very important practical significance to improve the level of railway construction project management in our country .
2014 Vol. 31 (9): 1-7 [
Abstract
] (
5096
)
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258
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8
New Analysis Method of Seismic Passive Earth Pressure and Its Distribution on a Retaining Wall
ZHANG Guo-xiang, ZHANG Hong-bin, AN Guan-feng
Research purposes:At present, the analysis methods about seismic passive earth pressure and its distribution have several defects, including unreasonable distribution rule and position, complex derivation, harsh application conditions and so on. The seismic passive earth pressure problem is translated into non-seismic passive earth pressure problem in this paper by using the transform method with rotating calculation model of retaining wall. This method has large reference value to simplify the calculation process of seismic passive earth pressure and its distribution.Research conclusions:Based on the non-seismic passive earth pressure formulations with horizontal slices analysis method, the analytical formulas of seismic passive earth pressure intensity distribution, resultant force of earth pressure and its point position are obtained directly, and the explicit solution of critical rupture angle is got by graphic method. The influencing factors including horizontal and vertical seismic accelerations,different angle of wall back,cohesion and external friction angle between filler and back of retaining wall,equispaced overloading are considered. The formulas can be used for seismic passive earth pressure calculations of cohesive soil with common border condition. The deducing process of seismic passive earth pressure formulations is simplified and unified greatly by using the method in this paper. The seismic passive earth pressure theory is perfected much more. The research results can be applied to do fast computation about seismic passive earth pressure of retaining wall.
2014 Vol. 31 (9): 8-12 [
Abstract
] (
4920
)
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353
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13
Research on the Relationship among Subgrade Bearing Capacity, Embankment Stability and Settlement
LI Jian-guo,WANG Xun, SUN Li-xun
Research purposes:In order to ensure the safety of railway or highway subgrade, subgrade bearing capacity, embankment stability and settlement which are the three main control indexes of subgrade design should be analyzed and checked in theory. However, many railway and highway designers still have differences on whether subgrade bearing capacity should be calculated in our country. Through analyzing the relationship among subgrade bearing capacity, embankment stability and settlement, the necessity of checking subgrade bearing capacity is discussed in this paper.Research conclusions:(1) It is unsafe that circular arc method is used to check the embankment stability, in the case that subgrade bearing capacity does not meet the requirements, the conclusion that embankment is stable can be also drawn. (2) The lateral displacement of subgrade will increase sharply when the load approaches or exceeds subgrade ultimate load, and the existing settlement calculation methods are no longer applicable. The application condition of settlement calculation methods is that the requirement of subgrade bearing capacity is met. (3) In order to ensure the stability of the embankment and control the settlement of it, the subgrade bearing capacity should be checked in the design of subgrade. (4) In this paper, the research conclusion can provide a theoretical basis for the further improvement of subgrade design method.
2014 Vol. 31 (9): 13-16 [
Abstract
] (
5088
)
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330
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17
Discussion on the Assessment of Initial Stress Field of Railway Rock Mass
HAN Kang, FU Kai-long, ZHOU Shu-qi
Research purposes:In actual work, according to the ground stress data for assessment, most railway tunnels are under very high ground stress and high ground stress state, which causes adjustment of surrounding rock and engineering measures to strengthen, thus these will cause large increased investment, even cause large dispute and chaos in analysis causes of tunnel lining cracking and deformation, but the engineering case that rock burst and large deformation occurred in actual excavation of tunnel is very rare. In this paper, according to rock mass mechanical theory, the ground stress information and engineering case, combined the relevant provisions of similar industry, the assessment of initial stress fields of rock mass in railway specification is discussed.Research conclusions:(1) The assessment of railway specification to initial ground stress field is not realistic and should be revised, preliminary judgment when the measured in-situ stress >30 MPa, the possibility of rockburst is increased. (2) Assessment conclusion of initial ground stress field should be discreet, the increased investment should be incorporated into the dynamic design. (3) The stress tests of survey design stage should be reasonable and appropriate. (4) The research results can be applied to the modification of railway norms and tunnel exploration.
2014 Vol. 31 (9): 17-20 [
Abstract
] (
4989
)
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65
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21
Contrast of Partial Coefficient Design Method and Design Method Based on Reliability Index
WEI Yong-xing, LUO Yi-nong, LIU Chang-qing
Research purposes:By contrast of concept, process, and examples of the partial coefficient design method and the design method based on reliability index, this paper has revealed the essence of the two kinds of design methods, namely for the design method based on reliability index, the concept of probability is directly introduced into design and for the design method of partial coefficient, the probability thought is reflected in the middle of the design, and has analyzed their common and obvious differences, which will provide the guidance for engineering design and research personnel to reasonably choose design method according to the actual situation.Research conclusions:(1) The partial coefficient design method, relatively simple, safe, suitable for conventional design, is a practical design method. (2) Reliable indicator design method, which can give attention to both safety and economy, the design process is complex, suitable for special design, is the ideal design way and the method of scientific research. (3) For the retaining structure engineering design, the partial coefficient method can be adopted. (4) The research conclusion has guiding significance for engineering design and research personnel to choose the retaining structure design method.
2014 Vol. 31 (9): 21-25 [
Abstract
] (
5083
)
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(399 KB) (
80
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26
Discussion on Retaining Structure Limit State Classification
LUO Yi-nong, LIU Chang-qing, WEI Yong-xing
Research purposes:Retaining structure belongs to the geotechnical engineering structure, the limit state classification of geotechnical engineering is more difficult than the structure projects. Based on the limit state concept at home and abroad, this paper makes a comparison and analysis of the common and difference of geotechnical engineering and structural engineering limit state, teases the retaining structure limit state and focuses on limit state of open-cut foundation and pile foundation, proposes the recommendation of limit state classification of retaining structure.Research conclusions:(1) The generalized limit state can be considered as a function which can achieve the expected requirements, the limit state is not limited to the concept of damage and failure, and its extension has been expanded to the requirements of that the goal of expected design cannot be achieved——a prescribed limit. (2) Retaining structure belongs to the category of geotechnical engineering, its limit state includes structure overall stability limit states and the structural stability limit state which includes the bearing capacity limit state and serviceability limit state and limit state between them, the state needs to be studied further. (3) In general area, the compressive stress limit state of open-cut foundation and lateral pressure limit state of rock foundation anchor pile foundation can be considered as the serviceability limit state. (4) The research conclusion is useful for guiding the design research of retaining structure limit state.
2014 Vol. 31 (9): 26-29 [
Abstract
] (
4906
)
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320
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30
Design Research of Gravity Retaining Wall Based on Limit State Design Method
LIU Chang-qing, LUO Yi-nong, WEI Yong-xing
Research purposes:Gravity retaining wall limit state design research is based on the design research of retaining structure limit state of open-cut foundation with the lateral earth pressure supported by wall body weight. This paper sums up the research thought of gravity retaining wall and analyzed their main calculation results, which provides reference for the open-cut foundation retaining structure design research of cantilever retaining wall, counterfort retaining wall, groove type retaining wall and so on.Research conclusions:(1) The steps for design research of the gravity retaining wall limit state are to establish a limit state equation, to calculate reliability index and determine the target reliability index, calculate partial coefficient and set up the design expression. (2) The most critical factor influencing gravity retaining wall limit state is comprehensive internal friction angle. (3) There are different function calculations and different design conditions for the gravity retaining wall in the current specification, their underlying reliability index is different, the corresponding partial coefficient should also be different. (4) The research conclusion can be used to guide the design of gravity retaining wall, which provides the reference to the design research of other open-cut foundation retaining structure.
2014 Vol. 31 (9): 30-34 [
Abstract
] (
5074
)
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(396 KB) (
92
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35
A Study on Seepage Field in Subgrade Slope Subjected to Various Rainfall Patterns
XIA Qiong, DOU Shun, WANG Xu
Research purposes:Rainfall is one of the most important factors for subgrade slope failure, and rainfall patter is one of the most primary influence parameters. Based on the two-dimensional saturated-unsaturated seepage theory, numerical analyses are conducted to investigate the change rules of seepage field in subgrade slope subjected to rainfalls with four different patterns, i.e. delayed, uniform, central and advanced rainfall patterns.Research conclusions:(1) Both the maximum pore-water pressure
u
max
and the maximum saturated depth
H
smax
at shoulder are affected by rainfall intensity and rainfall duration observably. (2) There is a sensitive range of coefficient of permeability influencing on the maximum saturated depth, only within the sensitive range increasing coefficient of permeability could reduce
H
smax
and subgrade surface pore-water pressure effectively. (3) Under central and advanced rainfall patterns, the most dangerous time stage of slope stability is obvious affected by coefficient of permeability, within the sensitive range and the less side outside the sensitive range, the starting point of the most dangerous time stage is not affected by coefficient of permeability, but the end time is advanced with coefficient of permeability increasing. (4) The stability of subgrade slope is the best under advanced rainfall pattern and the worst under delayed rainfall pattern. (5) The research results can provide basis and reference for slope protection and reinforcement design.
2014 Vol. 31 (9): 35-39 [
Abstract
] (
4926
)
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124
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40
Study on Horizontal and Vertical Temperature Gradient of Ballastless Track on Curve Line
DAI Gong-lian, SU Hai-ting, YAN Bin
Research purposes:In order to get the time-varying rules of temperature field distribution in the track structure with superelevation and build the horizontal and vertical temperature gradient of ballastless track, a continuous observation of CRTS Ⅱ by using temperature sensors on curve segment of a passenger dedicated line was held.Research conclusions:(1) The temperature change of ballastless track between daytime and nighttime is big, the temperature changing value of surface was 24.7℃ in maximum, 19℃ in average. (2) The temperature changing value became small and the time of maximum temperature come late with the increase of distance to surface. (3) At the bottom of the track structure, the temperature changing value was 6.1℃ in maximum, 5.0℃ in average. (4) Fitting curve of vertical temperature gradient of longitudinally connected ballastless track on curve line can be exponential curve, and the curve sharp can match the distribution about the vertical temperature gradient of the code for design of bridge and culvert in China. (5) The horizontal temperature gradient of the CRTS Ⅱ longitudinally connected ballastless track included the track slab and support layer, temperature gradient of track slab could be fitted by using quadratic function, temperature gradient of support layer could be fitted by using piecewise linear function. (6) This study can provide guidance for the temperature load model in the design of high speed railway in central China.
2014 Vol. 31 (9): 40-45 [
Abstract
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5155
)
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228
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46
Effect of Track Stiffness on Frequency Response of Vehicle-track Coupling System
WANG Ping, XU Jin-hui, WANG Li, CHEN Rong
Research purposes:Track stiffness is an important parameter for the design and maintenance of railway track. However, the frequency-domain influence of track stiffness on the vehicle-track coupling system is still not clear. Based on the theories of vehicle-track coupling system dynamics, taking the existing speed-increase line as an example, this paper explores the frequency-domain influence of track stiffness on the vehicle-track coupling system.Research conclusions:The influence of track stiffness on the vehicle and bogie is little and it influences the wheel set and the track structure a lot. With the increase of track stiffness, the vibration response of vehicle-track coupling system goes stronger obviously in the medium-high frequency band of 100 Hz above, but the vibration response in the low and medium frequency band of 27~70 Hz gets a little weaker and it shows nearly no influence on the vibration response in the low frequency band of 27 Hz below. As the stiffness of fastener system increases, the maximum values of wheel-rail force spectrum, the wheel set acceleration spectrum and the rail vibration acceleration spectrum all increase considerably and the vibration frequency shows a tendency to occur a frequency shift towards high frequency band. The similar rule can be found in the research of the stiffness of ballast bed. Overall, in the frequency domain, the stiffness of fastener influences the vibration response of vehicle-track system greatly while the stiffness of ballast bed affects the vibration response of vehicle-track system relatively weaker, so deteriorative fasteners should be replaced in time while the maintenance cycle of ballast bed can be extended appropriately. The research can provide a good guidance for the optimization design of track structure and the track maintenance.
2014 Vol. 31 (9): 46-52 [
Abstract
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5019
)
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122
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53
Influence of Fastener Stiffness Mutation in Ballastless Track on Dynamic Characteristics of High-speed Trains
LIU Xue-yi, ZHANG Zhong-wang, WAN Zhang-bo
Research purposes:The elasticity for the ballastless track structure is mainly provided by the fastening system. During the construction and maintenance of ballastless track on high-speed railway, the incorrect installation and the unreasonable transition between the old and new rail-pads may occur to the fasteners, which will cause a stiffness mutation for the fasteners. Even though this problem can hardly be found under the static condition, it can have a great effect on the stability and safety for the high-speed vehicle operation. Here different conditions for the fastener stiffness mutation are considered, according to the actually measured data. And the influence of fastener stiffness mutation on the dynamic performance of high-speed vehicle and track is calculated and analyzed by using the vertically coupled vehicle-ballastless track-subgrade vibration spatial model and the finite element software ANSYS/LS-DYNA.Research conclusions:The calculation and analysis results show that: (1)When there is a local mutation for the stiffness of fasteners, the maximum and minimum of vehicle acceleration basically keep the same. That is to say, the fastener stiffness mutation has few influence on the stability of vehicle operation. (2) The fastener stiffness mutation has much obvious effect on the wheel load reduction rate, which is related to the safety of vehicle operation. Further, when the train speed is larger than 300 km/h, the fastener stiffness mutation will directly cause the wheel load reduction rate to exceed the standard. (3) This research results can be used to provide a theoretical basis for monitoring the fastener stiffness in construction or repairing and establishing the strict control standards in high-speed railway.
2014 Vol. 31 (9): 53-58 [
Abstract
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5086
)
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59
Study and Application of Calculation Method for Temporary Consolidation Beside Piers in PC Cantilever Casting Beam
SUN Jiu-chun
Research purposes:The temporary consolidation at top piers is regarded as rigid body in continuous girder cantilever construction. And the calculation theory and method are mature. Whereas, temporary consolidation beside piers should be regarded as elastic body. And the calculation methods about it are insufficient. Through the mechanical analysis of temporary consolidation beside piers, a simple calculation method is proposed and can be applied in various construction conditions.Research conclusions:(1) Simplify the temporary consolidation beside piers as elastic three fulcrums model which is consistent with practical force-baring conditions. (2) Calculation method based on elastic three fulcrums model can be well applied in various construction conditions. (3) Calculation of axial forces temporary consolidation beside piers is well related to their tension-compression stiffness, and we should choose calculation formula based on their tension-compression stiffness and force-baring conditions. (4) The calculation method proposed can be the base and accordance for design of temporary consolidation beside piers in PC cantilever casting girders.
2014 Vol. 31 (9): 59-64 [
Abstract
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4931
)
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131
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65
Analysis of Train Derailment after Hitting the Pier of Tongling Yangtze River Bridge Combined Road with Railway
FANG Hai, SUN Hui-ming, LIU Wei-qing, MAO Yi-feng, ZHANG Qiang
Research purposes:Precise prediction for mechanical behavior of the bridge under ship collision force is important to assess the analysis of train derailment after hitting the pier. This paper focuses on the Tongling Yangtze River Bridge Combined Road with Railway for ship collision simulation, uses the nonlinear finite element software of ANSYS / LS-DYNA to simulate the ship's bow section of 10 000 t and 5 000 t class hitting bridge tower column at front and axle to 20° of side in highest navigable water level, conventional navigable water level and the minimum navigable water level. Curves of collision force-period at different working conditions are summarized. On this basis, when the impact load affects as input loads, the displacement and acceleration response can be used by finite element analysis under the collision and study the dynamic response of the bridge caused by a train derailment risk.Research conclusions:(1) The impact force of the bridge is largest when a laden ship is hitting the pier at the highest navigable water level. In the most unfavorable condition, the collision have lardge impact on bridge structure and derailment risk of trains. (2) The transverse acceleration of the girder on the top of 2
#
pier can reach to 0.922 m/s
2
, but it does not exceed acceleration excitation limit (1 m/s
2
) when 3
#
piers are hitted by the 10 000 t ship at the peak load of collision, so the probability of train derailment is minimal. (3) Based on the probability formula of the derailment by simplifying risk criteria, the derailment probability of train is 9×10
-5
~1.5×10
-4
during the ship-bridge collision. (4) The research results can provide the reference for train traffic safety on railway bridge caused by ship collisions.
2014 Vol. 31 (9): 65-70 [
Abstract
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4976
)
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170
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71
Research on the Law and Controlled Limit Value of Transverse Deformation for Shield Tunnel in Soft Clay
ZHU Bin
Research purposes:The transverse deformation of shield tunnel may deeply threaten the safety of tunnel structure.Excessive deformation may lead segment joints to open and leak and segments to craze. The deformation may even cause insufficient cross-section limit and the missing of structural-load-carrying capacity of the tunnel. On the other hand, it costs a lot to repair and reinforce the shield tunnel. In order to determine the proper moment to repair segments and ensure the safety of tunnel structure as well as economical efficiency, it is necessary to study the deformation law and limit value of the transverse section of the tunnel.Research conclusions:Based on the analysis of the influencing factors to causing the transverse deformation, the following conclusions was proposed: (1) The root of transverst deformation is increase of vertical and horizontal load ratio. (2)The shield tunnel properties of Nanjing Metro Line 2 was adapted to analyze the relationship between the variation of tunnel horizontal diameter andmaximum rate of joint opening,tress rate of both bolt and concrete using numerical simulation, furthermore the controlled limit value of transverse deformationwas got,the bolt tress achieve maximal strength when the variation of tunnel horizontal diameter reach 123 mm for sequential segment seams,and 127 mm for staggeredsegment seams, which means severely threaten to the safety of shield tunnel. Finally the precontrol and governance methodswere delivered to different influencing factors. (3)The research results can provide references to determine the controlling methods and restoration moment of the transverse deformation.
2014 Vol. 31 (9): 71-76 [
Abstract
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5178
)
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214
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77
Tunnel Deformation Monitoring System Based on Multi-agent Technique
ZHOU Qi-cai, FAN Si-xia, ZHAO Jiong ,XIONG Xiao-lei
Research purposes:In order to eliminate low frequency and high cost factors in traditional tunnel monitoring and maintenance, a new tunnel deformation online monitoring system based on multi-agent is proposed. It can adapt to the new requirements for real-time monitoring maintenance.Research conclusions:(1) Based on the hierarchical component structure design idea, this paper presents a general agent model. The model consisted of three layers, which were customer perception layer, intelligent service layer and service effect layer, respectively. The internal structure of the agent was descripted separately in coarse-grained and fine-grained. (2) According to the characteristics of tunnel deformation monitoring and the general agent, a tunnel deformation monitoring system has been set up using acquaintance cooperation communication mechanism, with six-layer composite structure. Additionally, this system could realize the loosely coupled ability and low load structure. (3) The performance of prediction agent module has been validated with Shanghai metro deformation monitoring data. The experimental results showed that the system had strong autonomy, cooperation and a certain practical value, and may give references to the construction of the tunnel monitoring system.
2014 Vol. 31 (9): 77-82 [
Abstract
] (
5171
)
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(1 KB)
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135
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83
Security Analysis of Neighborhood Shallow Undercut Tunnel Under-traversing Dense Buildings
ZHANG Hang
Research purposes:Affected by the complex urban environment, sometimes the construction of urban tunnels inevitably traverse under buildings. In order to reduce the demolition of buildings,this paper studies the settlement volume of ground surface and settlement regularity of roof buildings in conditions of different construction methods by means of numerical simulation of neighborhood soft-rock shallow undercut tunnel, furthermore, it analyzes the security of buildings above the tunnel.Research conclusions:(1) Settlement of ground surface caused by construction mainly depends on geological conditions, buried depth,excavation span of tunnel and construction method which is the most obvious. (2) On the basis of simulation and monitoring results, neighborhood shallow undercut tunnel under-traversing buildings adopts CD construction method as well as advanced small pipe to grout reinforcement of surrounding rock, the ground surface settlement can be effectively controlled,the safety of roof buildings can be protected. (3) The results of this study are mainly used in the field of city tunnel project, it can be referred by similar engineering’s design and construction.
2014 Vol. 31 (9): 83-87 [
Abstract
] (
5108
)
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(1 KB)
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(882 KB) (
93
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88
Warning Standards Study of Real-time Monitoring for Anti-collapse in Large Cross-sefction Tunnel of Soft and Weak Surrounding Rock
MA Shi-wei, HAN Xue-quan, LIAO Kai, DU Jun
Research purposes:The statistics for tunnel disasters showed that the quantities and casualties of tunnel collapse are much higher than other tunnel disasters. Achieved warning before collapse in tunnel construction, can greatly reduce the tunnel collapse hazards. The key to achieve anti-collapse warning in soft and weak surrounding rock tunnel is to obtain anti-collapse warning standards. Therefore, it is necessary to study tunnel anti-collapse warning standards to guide safe tunnel construction.Research conclusions:(1) Deformation of the tunnel is relevant to hydrogeological conditions, construction method, construction progress and other factors. Currently, the standard values in criterion were not suitable for tunnel collapse warning. (2) It is practicable to achieve anti-collapse monitoring by relative deformation, because anti-collapse real-time monitoring focused on dome relative deformation differently from routine monitoring in soft and weak surrounding rock tunnel. (3) The reference value of tunnel anti-collapse real-time monitoring is determined by displacement limit value in criterion, the maximum value of the measured displacement in similar project and the measured data in tunnel project. (4) The field experiment indicated that the reference value could meet tunnel anti-collapse warning. Therefore, the research results can be applied to large cross-section tunnel of soft and weak surrounding rock.
2014 Vol. 31 (9): 88-92 [
Abstract
] (
5045
)
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(1 KB)
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(416 KB) (
140
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93
Regularity Analysis on Transient Over-voltage of Grounding Gridby Lighting Strokes in Substations
LI Han-qing, FAN Chun-lei
Research purposes:Lightning has been one of the important factors endangering safe and reliable operation of the railway. The grounding grid performance plays a particularly important role in lightning protection. In this paper, the author has established a grounding grid transient model by the electromagnetic transient analysis software and intended for quantitative analysis of typically grounding grid layout in engineering practice, to lay important theoretical basis for future lightning protection and grounding.Research conclusions:(1)The results show that the ground potential is significantly affected by the soil resistivity, lightning current amplitude and the mesh size. With increase of the soil resistivity and lightning current amplitude, the ground potential at the point of the lightning current injection will significantly improve, but due to the spark discharge of the soil. The ground potential does not increase exponentially with potential lightning current amplitude. The smaller the mesh size, the better the ground potential attenuation. For example of the lightning current 20 kA and the soil resistivity 100 Ω·m, the ground potential of the 5 m×5 m mesh decreases 22.3% compared with the 10 m×10 m mesh.(2)The study finds that the ground potential attenuation away from the lightning strike point at 15m basically reaches the maximum, which is about 89%. And the degree of attenuation is independent of lightning current amplitude. (3)The results are mainly used for optimization program and design fields on substation lightning protection and grounding.
2014 Vol. 31 (9): 93-96 [
Abstract
] (
2636
)
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(1 KB)
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(526 KB) (
220
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97
Research on the High-speed Railway Catenary Systems Online Real-time Testing
WANG Xiang ,WANG Zheng-xing, CHAI Xiao-peng
Research purposes:Some catenary system vibrated largely after the train since Chinese high-speed railway running, which came from an oral report of one rail worker on duty. Its accurate displacement must be measured in order to solve the problem. The measurement technique based on image has the advantages of non-contact and dynamic which is suitable for unique structure such as catenary system. The computer gets displacement value through analyzing image which may ensure train's safety when on-line test is carrying out. The research not only can be used to analyze the cause of abnormal existing catenary shaking and swaying amplitude, but also can provide the technical support for catenary of electrified railway online real-time test.Research conclusions:(1) The measured amplitude of cantilever, shoulder brace of positive feeder and carrier cable was small relatively and consistent with other normal sections of the whole line. (2)The interaction between catenary and pantograph was the main reason for its vibration,without the coupling effect between up-bound and down-bound. (3) The accurate value of test result indicated that the amplitude of catenary is under the range allowably, which verified the uncertainty of human sense and further clarified the safety hazard. (4) The non-contact measurement technique based on image can get the dynamic real time test data and have simple and convenient operation, which supplies subtle and suitable way for high-speed railway catenary systems real-time on-line test.
2014 Vol. 31 (9): 97-101 [
Abstract
] (
2725
)
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102
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102
Research on the Thrust Output of a Long Primary Double-sided Linear Induction Motor
ZHANG Kun-lun,LIU Xi-jun, ZHANG Wen-long
Research purposes:Based on Maxwell equations and T-type equivalent circuit of linear induction motor, we analyze the electromagnetic thrust output of a double-sided linear induction motor in the case of edge effect, and use the finite element method and simulation to test the effectiveness of the theoretical calculation. We further derivate the mathematical expressions of a double-sided linear induction motor, build the simulation model by parameter design, and experimentally analyze the slip frequency control thrust output in conditions of different operating. Through analysis of the output characteristics of the electromagnetic force, optimal control of constant current slip frequency is achieved.Research conclusions:(1) We calculate various mechanical properties of a bilateral linear induction motor through its mathematical model and equivalent circuit, and derive the corrected coefficients of the horizontal and vertical edge effect. When the motor runs at a high speed, the edge effect has little influence on the output of the electromagnetic force. (2) We use the finite element computer software to establish the simulation model of a bilateral linear induction motor, and compare the theoretical calculation and simulation data: the simulation results are consistent with theoretical calculation, thus ensuring the validity of the mathematical model. (3) We simulate and analyze the influence of slip frequency, speed, suspension air gap, and length of the mover on electromagnetic force. At different speeds, properly adjusting the slip frequency can increase the output of electromagnetic force. For low speed, the optimal slip frequency is near 2 Hz; for high speed, the optimal slip frequency is between 4.0 Hz and 6.0 Hz. When satisfying the motor′s rated condition, the optimal control of electromagnetic force is achieved. (4) The research result of double-sided linear induction motor can provide important implications for the electromagnetic launch system of an aircraft carrier.
2014 Vol. 31 (9): 102-107 [
Abstract
] (
2700
)
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(1 KB)
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(677 KB) (
135
)
108
Deep Foundation Pit Excavation Procedure Optimization Considering Creep Deformation on Nearby Metro Tunnel
LIU Ji-qiang,LI Yuan-hai,LIN Zhi-bin,GUI Chang-lin
Research purposes:The existing researches about excavating procedures of deep foundation pit on nearby metro tunnel in soft formation are lack of systematicness, and creep characteristics of soft clay are not usually taken into consideration. This paper takes Qianhaiwan station of Metro Line 11 in Shengzhen as engineering background and considers creep characteristics in sludge formation. The influence of step excavation in the transversal,longitudinal and vertical directions on the deformation of foundation pit and nearby subway tunnel are simulated, which may be expected to provide theoretical basis for choosing foundation pit excavation procedure of Qianhaiwan station.Research conclusions:(1) The segment far away from tunnel should be excavated firstly when only transversal step excavation was undertaken along the horizontal direction of foundation pit. (2)The maximum horizontal displacement of the piles show exponential relations with the number of segments when step excavation of foundation pit was undertaken in vertical and transversal or longitudinal. If thickness of every step excavation was limited in 1.5~2 m, the horizontal displacement of the pile near tunnel can be reduced about 9 percent when there is no horizontal step excavation. (3) Transversal step excavation with segments far from tunnel excavated firstly was found to be the best step excavation method under the same condition of step number and support, and longitudinal and transversal step excavation followed while longitudinal step excavation was the last. (4) The research results have guiding significance for foundation pit of Qianhaiwan station and similar projects.
2014 Vol. 31 (9): 108-114 [
Abstract
] (
2656
)
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(1 KB)
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(2146 KB) (
88
)
115
Multi-Resolution Modeling and Simulation for Urban Rail Transit Network Planning
JIANG Xi,MIAO Jian-rui, LIU Jun
Research purposes:Simulation technology plays an important role in the urban rail transit network planning and analysis. With the enlargement of the urban rail network scale,the complexity and difficulty in the development of simulation system for urban rail transit network planning increase.To develop the simulation system with high efficiency, an approach to multi-resolution modeling and simulation of urban rail transit system is presented.Research conclusions:(1) An approach to build a multi-resolution simulation system of urban rail transit is presented, by building and integrating transit network architecture models and passenger models in different resolutions. (2) Ahierarchical model of rail transit network topology is built to resolve the problem of spatial consistency in multi-resolution modeling. (3) A polymerization based station simulation model is built to resolve the problem of state consistency. (4) To meet the needs of extensibility and flexibility of the simulation system, an agent-based integration method is applied to develop the simulation system of urbanrail transit network. (5) Arealized example on the application of the simulation model is introduced,which is used to analyze and evaluate a transit network planning.
2014 Vol. 31 (9): 115-120 [
Abstract
] (
2787
)
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(1 KB)
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(1527 KB) (
209
)
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Research on the Utilization of Regenerative Energy of Rail Transit Traction System
LI Li-peng, SHENG Jia-chuan
Research purposes:Widely used in urban rail transit, the VVVF multiple unit trains will generate a mass of energy when they are braking. If this part of energy can be used effectively, it will be of great significance for the energy-saving and cost-reducing of the whole rail transit. At present, there are several kinds of regenerative energy utilization proposals. But difference of saving effect of different schemes is very large, and part of proposal may lead to a waste of energy. Therefore, it is necessary to combine theoretical calculation with practical measurement and make comprehensive analysis on the energy saving effect of current regenerative energy utilization proposals.Research conclusions:This paper constructs the model of rail transit traction power supply system and studies the calculation result and measurement result. The experiments show that: (1)The regenerative energy utilization rate is very high between the vehicles when no regenerative energy absorption devices are installed in traction substations. (2)Traditional proposal of putting regenerative braking resistor in traction substation may not save energy, on the contrary, it will waste energy. (3)When the capacity of electricity utilization device reaches a certain value, the additional capacity will make very little effects on energy saving effect. (4) The research results can be used in the design of rail transit traction power supply system.
2014 Vol. 31 (9): 121-128 [
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