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.     

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.     

Impact Analysis of the Reduction Effect for Reducing Joint Position of Stick-slip Fault TunnelEI北大核心

Research purposes: Based on an engineering of traffic tunnel, anti-breaking model experiment of large-scale 1 :30 is carried out under fault dislocation. Reduction effect of three working conditions(working condition A of no reducing joint, B of staggered setting of reducing joint and dislocation surface, C of reducing joint set at dislocation position) is comparatively analyzed by analysis of contact pressure, lining strain and lining stress. The optimal location of reduction joint is explored. Research conclusions:(1)The reduction effect of different position of reducing joint is different, such as A相似文献   

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.     

Analysis of train derailment after hitting the pier of tongling yangtze river bridge combined road with railwayEI北大核心

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 10000 t and 5000 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/s2, but it does not exceed acceleration excitation limit (1 m/s2) when 3# piers are hitted by the 10000 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.     

Research on the Cause and Influential Factors of Tunnel Lining Cracking of Side Wall in Seasonally-frozen RegionsEI北大核心

Research purposes: In recent years, tunnel diseases like lining cracking and water leaking during spring thawing period, caused by frost heaving of surrounding rock, have occasionally occurred in high-latitude seasonally-frozen regions of northwest China and northeast China, which has seriously affected the tunnel structure and operation safety. Taking several railway tunnels in northwest China as an example, this paper investigates the cause and main influencing factors of longitudinal cracking of side wall in winter in seasonal frozen soil area by means of field test, laboratory experiment and numerical simulation. Research conclusions:(1) When the water content of surrounding rock of tunnel built in strongly-weathered sandstone is 12.3% and the frozen depth of surrounding rock is up to 60 cm, the maximum tensile stress of side walls is 2.28 MPa, which is larger than the ultimate tensile strength of C30 concrete, then the horizontal lining cracking will appear on side walls under the effect of continuous negative temperature in winter. If the lining bears part of the surrounding rock load, the longitudinal cracking degree of the side wall will increase. (2) Under the effect of frost heaving loads, the cracking of tunnel lining has its own characteristics of symmetry, seasonality and accumulation, etc. The cracks appear in winter and distribute in the middle of side walls. As the temperature is rising, the crack begins to shrink. (3) The frozen circle thickness and water content of surrounding rock should be used as main indicators during the process of calculation of frost heaving loads of surrounding rock in seasonally-frozen regions. (4) The research results can be used for reference in tunnel design, operation and maintenance in seasonal frozen soil area. © 2018, Editorial Department of Journal of Railway Engineering Society. All right reserved.     

The Methodology Research on the Test and Evaluation of Static Stiffness of Elastic Pads in Elastic Separated FastenerEI北大核心

Research purposes: In order to explore the reasonable test and evaluation methods of the static stiffness of the elastic pads in elastic separated fastener, the influences of various factors on the static stiffness of the elastic pads were tested and analyzed by single factor test, a reasonable static stiffness test plan for the elastic pads was proposed. Besides, the evaluation suggestions for static stiffness of rail pad and baseplate pad were analyzed in terms of the installation state of the elastic separated fastener. Research conclusions:(1) The test of the static stiffness of elastic pad should include two stages: preloading stage and formal loading stage. Firstly, the elastic pad shall be preloaded with no less than 2 times at a loading rate of 3-5 kN/s, and the preloaded maximum load shall be at least 10 kN higher than the static stiffness test load range of the elastic pad. Then, formal loading is supposed to be carried out at least 3 times with a loading rate of 1~2 kN/s, and at both ends of the load range the load should be maintained for 90 s, which could be shortened to 60 s in special case when the load is less than 100 kN. Finally, the static stiffness of the elastic pad is calculated by the average value of the three test results. (2) The evaluation methods of static stiffness of rail pad and baseplate pad are dissimilar. The static stiffness of the rail pad could be evaluated by the secant stiffness in the range of 20~70 kN, while the evaluation of static stiffness of baseplate pad should be processed in terms of the reasonable static stiffness test load range of baseplate pad determined by the installation torque of anchored bolt. (3) This research results can be applied in the test and evaluation of static stiffness of rail pad and baseplate pad in elastic separated fastener. © 2018, Editorial Department of Journal of Railway Engineering Society. All right reserved.     

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.     

Prediction and Control of Wheel/Rail Noise for Rail Transit(Abstract of the Ph.D.Dissertation)

On the basis of the theory of vehicle-track coupling dy-namics and noise radiation and propagation,a model ofwheel/rail noise prediction for the rail transit is founded andthe software for wheel/rail noise prediction is developed.Inthe model,the wheel is …     

Posterior only pedicle screw construct for the Treatment of Scoliotic Curves Greater than 90 Degrees

Abstract: Study design. A retrospective comparative study Objectives. To assess the efficacy and safety of posterior only pedicle screw construct (POPS) for the treatment of scoliotic curves > 90 degrees using radiographic outcomes and various clinical outcomes. Summary of Background Data. A paucity of data exists regarding standardized surgical options for severe scoliotic curvatures > 90°. Perioperative traction or staged anterior and posterior operations were the traditional surgical options. Methods. A total of 40 consecutive scoliosis patients with curves > 90° (average 111.4°; range 91°-175°) with an average follow-up of 31 months; range 6-60 months) who underwent spinal instrumented fusion with posterior only pedicle screw constructs performed by a single surgeon were analyzed. Diagnoses included idiopathic scoliosis (n=27), congenital (n=9), neuromuscular (n=3), and syndromic (n= 1). In total, 25 patients were treated with posterior only pedicle screw constructs with multiple Ponte ostotomies while the other 15 patients with posterior vertebral column resection. Radiographic examinations and complications were analyzed. Results. Radiographic outcomes demonstrated an average major curve correction of 49 % and 47% at eight weeks post operation and final follow-up respectively (p<0.001). Total deformity angle, major Cobb angle + maximal kyphosis with an average of 160 degrees preoperatively, showed an average correction of 50 % and 48% at eight weeks post operation and final follow-up respectively (p<0.001). There were seven cases (18%) of intraoperative MEP (motor evoked potential) loss and four patients (10%) with transient spinal cord deficit. One patient developed postoperative infection. Another patient had a unilateral broken rod in two years follow-up which was treated with observation. Conclusion. Scoliosis patients with curve > 90 degree can be managed successfully by posterior only pedicle screw construct (POPS). POPS avoids the need for anterior surgical procedures or perioperative traction while achieving acceptable correction safely without significant complication.     

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.     

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.     

Research on the Mechanical Characteristics of Primary Supporting in Deep Buried Large-section Red Clay TunnelEI北大核心

Research purposes: In the New Austrian Tunneling Method, the primary supporting has the vital function as the main structure of taking the pressure of surrounding rock. In order to study the force characteristics of primary supporting in the composite lining of deep buried large section tunnel, this paper is based on Qingyang tunnel engineering in Yinchuan-Xi'an High-speed Railway. After the on-site monitoring of the process, we can find the variation law of surrounding rock pressure on the deep buried large section red clay tunnel, steel arch internal force and concrete internal force, and analyze the internal forces and distribution characteristics of the primary supporting structure. Research conclusions:(1) The pressure of surrounding rock on both sides of the large section tunnel of red clay is greater than that in the vault and the inverted arch. (2) The internal force of primary supporting structure shows a distribution pattern of big top and small bottom, and the steel arch bears most of the surrounding rock pressure. (3) It can be considered to increase the marking of steel arch frame on the side wall and vault roof, and reduce the section area of arch frame in inverted arch, so as to make full use of materials, reduce the cost and improve the reliability of lining structure. (4) This research conclusion can provide reference for the optimization of lining design and construction organization of tunnel primary support under similar geological conditions. © 2018, Editorial Department of Journal of Railway Engineering Society. All right reserved.     

Research on the Design of Career Development Channel for Employees in Large State-owned Construction EnterprisesEI北大核心

Research purposes: From the factors and the principles the enterprise employees' career development design should consider, this paper studied and further discussed channel setting, the division of hierarchy and width, positions or proportional control of all levels, qualification criteria of all levels to determine, career development path management, to solve the problems of the large state-owned construction enterprise, such as narrow development channel, less promotion platform, and insufficient continuous motivation of professionals, technical operators, and general management personnel, resulting in employees no passion, no fighting will, not dedicated, difficult to bring in talents and high attrition rates of talents. Research conclusions:(1) The design of employees' career development should consider four aspects: attractiveness, operability, practicality and pertinence. (2) The design of employees' career development should follow the principles of systematic, overall and long-term development. (3) The design of career development channel should be mainly considered from the aspects of post setting, channel hierarchy and width division, and job qualification criteria. (4) The research results can provide a reference for the design and research of career development channels for employees in state-owned construction enterprises. © 2018, Editorial Department of Journal of Railway Engineering Society. All right reserved.     

Research on the Influence of Small Distance Subway Tunnel Passing through Buildings at Short DistanceEI北大核心

Research purposes: At present, the urban subway is developing rapidly in our country, among which there are many problems. This paper takes a seven-story frame structure office building as research object. In view of the phenomenon that the dome subsidence and the land subsidence rate exceed the early warning in the field construction of the left line tunnel, combing theoretical analysis with the MIDAS-GTS numerical simulation, we took the "building-stratum-tunnel" as the research object, analyzed the influence of small distance tunnel construction process of mine method on the adjacent buildings, and analyzed the influence difference of the construction sequence of the left and right lines. Finally we put forward the relevant engineering technical measures. Research conclusions:(1) The tunnel construction makes the building in the tensile zone, and the structure is easy to be damaged. When the structure is far away from the influence of the excavation, the order of tunnel excavation is not significant. (2) When the surrounding rock is broken and close to the building, it is better to excavate the tunnel far away from the side of the building. At the same time, we should pay attention to taking the reinforcement measures near the side of the building and the intermediate rock column. (3) The research results can be applied to the field of shield construction in subway, and have a good guiding effect on the shield tunnel passing through buildings at close distance. © 2018, Editorial Department of Journal of Railway Engineering Society. All right reserved.     

Research on the law and controlled limit value of transverse deformation for shield tunnel in soft clayEI北大核心

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.     

The Reinforcement Analysis of Prestressed Anchor Frame Beam in the Deep Cutting Slope under Three Dimensional Strong EarthquakeEI北大核心

Research purposes: In order to further study the reinforcement of prestressed anchor frame beam in the deep cutting slope under three dimensional strong earthquake, a model of the deep cutting slope is built through FLAC 3D simulation software, the seismic wave to the model from three directions of x,y and z is input, and the dynamic response of the slope is analyzed. Then, the prestressed anchor frame beam reinforcement measures are applied to the model, and this paper analyzes the reinforcement effect of the prestressed anchor frame beam to the deep cutting slope under three dimensional strong earthquake. Research conclusions:(1) The prestressed anchor frame beam has a good effect on restraining the horizontal displacement of the deep cutting slope. (2) Under the three dimensional strong earthquake, the prestressed anchor frame beam has a good effect on the horizontal acceleration and horizontal velocity of the deep cutting slope, which reduces the peak of horizontal acceleration and horizontal velocity. (3) Through the comparison of the response before and after the reinforcement of the prestressed anchor frame beam is given under the 9 degrees three dimensional strong earthquake, it can be concluded that the prestressed anchor frame beam can provide good reinforcement effect to the deep cutting slope. (4) This research can be used for reference to the earthquake resistance of the slope engineering. © 2018, Editorial Department of Journal of Railway Engineering Society. All right reserved.     

ces for the Cenozoic evoluti

day. Base on the new field works in Shuanghu and Tuotuohe regions of central Tibet by us and the datum have been obtained by other researches on the grabens. We proposed that, the graben structures are distributed in the most part of plateau; including Himalayan, Gangdese and Qian     

Analysis of collapsibility of loess in real soaking environment and grading of soaking environmentEI北大核心

Research purposes: The analysis of the soaking condition and mechanism of the Loess under the real environment condition was made, the thicknesses of the saturated collapsible loess layers under most unfavorable natural and artificial environments were determined, and the soaking collapsible environments were graded according to the influence differences of the environment on the loess soaking. Research conclusions: The real collapsible thickness of loess depends on a variety of factors and the major factor is the soaking condition. Under the concrete soaking condition, the thickness of saturated collapsible loess is controlled by the precipitation, penetration of surface water and rising of ground water. The experience and calculation show the most soaking thicknesses under natural environment are obviously less than the thickness of the collapsible loess. By taking the soaking collapsible thickness as the basis, the construction cost and works can be much reduced. The calculation and analysis of the soaking thickness under natural environment presented in this paper can give a new method and thinking on valuation of the loess collapsibility and grading the soaking environment.     

Analysis of damping performance of isolated rubber floating slabEI北大核心

Research purposes: The basic component of the track structure with isolated rubber floating slab is the concrete slab track born by the elastic element. The research was done on the mechanical properties of the floating slab, the analysis was made for the natural frequencies, mechanical response under dynamic load and damping performance, and the discussion was made on the reasonable thickness of the ballastless track to provide the reference to the track design. Research conclusions: The research results show that the natural frequency of the track system decreases with the increase of the thickness of the ballastless track, and the rate of change decreases with increase of the track thickness. The acceleration insertion loss of the track basis increases with the increase of the thickness of the ballastless track, and the rate of change decreases with increase of the track thickness. When the thickness of the ballastless track reaches at 0.4 m, the corresponding dynamic performance, the damping performance effect and the concrete amount of track bed are rather economical. From the present theoretical analysis and online testing, it can be seen the damping performance effect of the isolated rubber floating slab system is obvious, and its construction and maintenance programs are systematic.