Research on the Mechanical Properties of Transparent Sand Based on Triaxial TestEI北大核心

Research purposes: Transparent sand is a new type of geotechnical engineering material, which is made of fused silica sand and porous liquid with the same refractive index. In order to understand its mechanical properties, the CU and CD tests of fused silica sand with a particle size of 0.5~1.0 mm and 1.0~3.0 mm are carried out by triaxial apparatus, and the stress-strain curves, pore water pressure changes and effective stress ratio of the two are compared and analyzed. In addition, E-μ model parameters of coarse and fine sand are calculated respectively, which provide corresponding parameters for further numerical calculations. Research conclusions:(1) The loose sample's stress-strain curve shows hardening characteristics. (2) The coarse particle specimen with steeper stress-strain curve comes to the peak at faster velocity than fine particle specimen. (3)The pore pressure value of the coarse particle specimen is greater than the fine particle, the pore water pressure coefficient of the two shows a decreasing trend with the increase of the confining pressure. (4) Transparent sand can be used to simulate natural sand and the change of diameter can represent different soils. (5) The research results can provide reference for model tests based on transparent soil technique. © 2018, Editorial Department of Journal of Railway Engineering Society. All right reserved.     

Study on horizontal and vertical temperature gradient of ballastless track on curve lineEI北大核心

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.     

Research on the Influence of Vertical Deformation of Bridge on the Track RegularityEI北大核心

Research purposes: The vertical deformation of high-speed railway (HSR) bridge will cause the track irregularity, which threatens the safe and efficient operation of the HSR. Taking the 32 m simple supported beam bridge as the research object, based on the existing mapping analytical model for bridge vertical deformation and rail geometry, the influence of the track regularity of the CRTS Ⅰ slab ballastless track structure caused by the key parameters such as the bridge vertical deformation amplitude, the hanging length of the beam end and the vertical stiffness of mortar layer were studied, and the corresponding measures to control the rail deformation were proposed, to provide theoretical reference for comprehensive treatment of rail deformation of HSR bridge. Research conclusions:(1) The pier settlement, the vertical rotation of the beam end and the beam fault will cause the rail to follow the beam deformation, and "up-warping" of the rail on the vertical deformation boundary will appear. (2) The rail deformation is directly proportional to the vertical deformation amplitude of the bridge and the key to control the rail deformation is to reduce the vertical deformation of the bridge. (3) The rail deformation can be controlled by reducing the hanging length of beam and vertical stiffness of mortar layer. (4) The research results can provide a theoretical reference for controlling the vertical rail deformation of high-speed railway bridges. © 2018, Editorial Department of Journal of Railway Engineering Society. All right reserved.     

Research on minimum headway between EMU and common passenger train on passenger dedicated lineEI北大核心

Research purposes: The minimum headway of trains is an important technical standard in the railway survey and design. The common passenger train running on passenger dedicated line (PDL) has big influence on the headway between trains. This paper mainly analyzes the type of coach, passenger train composition and train operation control system, and presents the calculation method and model for the headway between the EMU and common passenger train for providing the reference to the survey and design of passenger dedicated line. Research conclusions: Based on the technologies of the train control system level 2 (CTCS-2), the train running monitor and record device (LKJ) and the ground signals, the analyses and calculations were made for the minimum headways between trains into the Yuncheng North Station of Datong-Xi'an PDL by using the calculation model. The calculations show the 3 minutes headway of the arrival-running through, the 3 minutes headway of the arrival-arrival and the 3 minutes headway of the running through-departure between the common passenger train and the EMU can be realized. And the 5 minutes headway of the departure-departure between the EMU and the common passenger train can be realized.     

Research on the Influencing Factors on Quality of Railway Construction EPC Project from the Owner's PerspectiveEI北大核心

Research purposes: With the advancement of system reform of China railway, the railway construction project is promoting the application of general contracting (EPC) model, and in this mode, how the owners effectively control the construction quality has become the focus of the current research. To explore of the key factors influencing quality of railway construction project, based on the owner's perspective, from the three stages of design, procurement and construction selecting 10 factors, the DEMATEL method is adopted to analyze the logical relationship between various factors and mutual influence, screening factors which have higher centrality and causality as the key factors affecting the quality of the owner engineering. Research conclusions:(1) The design port and interface management, the comprehensive strength of the construction companies have high centrality and causality, which are the key factors influencing quality of the EPC railway construction project. (2) The situation of carrying out periodic inspection work belongs to the factor with low centrality and high causality. In the process of improving quality of the EPC railway construction project, this factor can be the secondary consideration. (3) The research result can provide scientific and effective references for improving quality of the EPC railway construction project from the owner's perspective. © 2018, Editorial Department of Journal of Railway Engineering Society. All right reserved.     

Discussion on retaining structure limit state classificationEI北大核心

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.     

Research on the high-speed railway catenary systems online real-time testingEI北大核心

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.     

Research on deformation failure mode of slope diseases caused by earthquakeEI北大核心

Research purposes: The slope diseases caused by earthquake are different from other types of slope diseases in general. They have various mechanism and deformation failure modes and can cause large damages. In order to prevent and control these diseases pointedly, based on investigations of 3 slope diseases along the Wenchuan-Yingxiu Road influenced by the "5·12"Wenchuan Earthquake, the analyses and researches were made and done on the slope diseases types, slope structures and mechanism to summarize the deformation failure modes of slope diseases caused by earthquake. Research conclusions: (1) The main types of slope diseases include the collapse, landslide, slumping, fault and rockfall. Collapse is the major disease, up to 71% of the total slope diseases. About 80% diseases happens to rock slope. (2) The deformation failure modes of collapse have 8 types like pull cracking and falling.Landslide has 5types like pull cracking, shearing off and sliding. Slumping has 2 types of shaking loose and slumping. Rock falling has 2 types of throwing and dropping. Disorder falling has 1 type of shaking to crimping. (3) This research result can provide the reference to prevention and control of the slope diseases caused by earthquakes along railways and roads.     

Study on Process Re-engineering,ProjectPlanand Process Integration in Electric-Mechanical Product Development Process

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Discussion on the assessment of initial stress field of railway rock massEI北大核心

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.     

Design research of gravity retaining wall based on limit state design methodEI北大核心

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.     

Contrast of partial coefficient design method and design method based on reliability indexEI北大核心

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.     

Research on the relationship among subgrade bearing capacity,embankment stability and settlementEI北大核心

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.     

Research on the thrust output of a long primary double-sided linear induction motorEI北大核心

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.     

Robust H∞ Fault Tolerant Control on Suspension System of Maglev Train with Delayed Input

以磁悬浮列车单模块悬浮系统为对象,考虑系统存在的输入时滞,建立了时滞悬浮系统的数学模型,基于状态反馈和线性矩阵不等式处理方法,设计了在执行器发生故障情况下的鲁棒H∞容错控制器,在此基础上,针对不同执行器故障模式,对悬浮间隙的变化情况进行了仿真.仿真结果表明所设计的控制器在执行器故障条件下能够使磁悬浮列车稳定悬浮与运行.     

A study on seepage field in subgrade slope subjected to various rainfall patternsEI北大核心

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 umax and the maximum saturated depth Hsmax 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 Hsmax 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.     

Theoretical Analysis and Experimental Study on Dynamic Interaction of Rail way Bridge and Articulated Trains

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Regularity analysis on transient over-voltage of grounding grid by lighting strokes in substationsEI北大核心

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 15 m 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.     

Deep foundation pit excavation procedure optimization considering creep deformation on nearby metro tunnelEI北大核心

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.     

Research on the management innovation and practice of construction for Beijing-Shanghai high speed railwayEI北大核心

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.