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.     

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   

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.     

Analysis of Passive Limited Supporting Force of Curved Shield Tunnel Excavation FaceEI北大核心

Research purposes: In the construction process of curved shield tunnels, the force of excavation face is extremely complex and the stability is difficult to control, so it is very likely that the thrust of the jack will cause uplift of the soil in front because of passive failure. Taking the sand strata as an example, this paper established a combination model of "inverted ladder-wedge prism" to reveal that the soil in front of the excavation face of curved shield tunnels uplifts up because of passive failure based on the silo theory and limit equilibrium method, and deduced the calculation method of passive limited supporting force for curved tunnels. Then, we confirmed the accuracy and reliability of this model and calculation method through programing and simulating. Research conclusions:(1) The passive limited supporting force increases with the increase of buried depth and internal friction angle, and the growth rate gradually increases. (2) When the radius of the line is less than 200 m and the internal friction angle is more than 25 degrees, the passive limited supporting force is very sensitive to the curvature radius, and when the radius is more than 800 m, the passive limited supporting force is almost no difference with straight tunnels. (3) The numerical results indicate that the numerical solution is consistent with the theoretical solution and the difference is quite small. (4) The research results can provide theoretical basis for determining the passive limited supporting force in the constructions of similar curved shield tunnels especially small turn radius shield tunnels. © 2018, Editorial Department of Journal of Railway Engineering Society. All right reserved.     

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.     

Multi-resolution modeling and simulation for urban rail transit network planningEI北大核心

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.     

Test Analysis of the Vibration Response of Trough Girder Bridge in the Small Radius CurveEI北大核心

Research purposes: The bridge in circinate line of Hefei Railway Hub was built in the curve with radius of 300 m. In order to reduce structural height of the bridge across the Huainan railway, the single-line simple trough girder bridge with 32 m span was applied. The lateral vibration of the vehicle and bridge is intensified under the action of centrifugal force, and the torsion effect is obvious when the train running on the bridge in the small radius curve. On the other hand, the torsional rigidity of the trough girder with open section is lower than that of the closed box girder. Moreover, the wheel lateral force and the derailment coefficient is increased, and the reduction rate of wheel load is also increased owing to centrifugal force caused by unbalanced superelevation. In order to ensure the safe and smooth operation of the train and reveal the dynamic performance of the trough girder bridge in the small radius curve, the vibration response of the single-line trough girder bridge is tested and analyzed. Research conclusions:(1) The measured vertical and horizontal fundamental frequencies of the trough girder bridge are obviously larger than the vertical self-vibration frequency limit given by the relevant specification and the normal value of the measured transverse minimum natural vibration frequency. The lateral stiffness of the bridge is mainly controlled by its foundation stiffness. (2) The stiffness of the bridge can meet the requirements of C62 freight train safe running on the trough girder bridge in the curve with radius of 300 m at a speed of not more than 40 km/h. (3) The transverse vibration response of the bridge consists of the transverse static response of the structure caused by the centrifugal force and the lateral dynamic response caused by the coupling vibration of the vehicle-bridge system. (4) The research results can be referenced in the design of the railway bridge in the curve and coupled vibration analysis of trains and bridge in the small radius curve. © 2018, Editorial Department of Journal of Railway Engineering Society. All right reserved.     

Warning standards study of real-time monitoring for anti-collapse in large cross-sefction tunnel of soft and weak surrounding rockEI北大核心

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.     

Study and application of calculation method for temporary consolidation beside piers in pc cantilever casting beamEI北大核心

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.     

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.     

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 fast detection system for foundation plate of ballastless track of high-speed railwayEI北大核心

Research purposes: A new detection method with the computer, the total station and senor technologies is presented for control of the elevation of the ballastless track of high-speed railway. By using the new control technology, the control of elevation of the ballastless track of high-speed can be achieved during construction. Meanwhile, the detecting efficiency can be enhanced, the construction schedule can be speeded up, the measurement and labor costs can be cut, and the one-touch operation and good visibility can be achieved by using the new measurement and mathematical model built with software system. Research conclusions: (1) Application of the fast detection system for the foundation plate of the ballastless track of high-speed can much enhance the construction measurement efficiency and facilitate the quality control during construction of foundation plate. (2) The detailed and objective data can be provided for the intermediate acceptance, and the detection methods with the independent intellectual property right have been formed during the research. (3) The combined test way and method are found for the relative and absolute benchmark measurements, and it fills the technological blank in this field and promotes the innovation and development of the automatic measurement equipment for construction of high-speed railway in China. (4) The detection system presented in this paper solves the quality control problem in construction of ballastless track of high-speed railway and can provide the reference to the similar project.     

A New Technique of High-performance and Fast Tensioning Prestressed Anchorage CableEI北大核心

Research purposes: The large-span transition section tunnel of the Badaling Great Wall station on the Beijing-Zhangjiakou high-speed railway with the maximum excavation width of 32.7 m, and the largest excavation area of 494.4 m 2 , is the world's biggest traffic tunnel in the world with the largest excavation width and excavation area, which has difficult construction and high security risks. The initial support system of tunnel is mainly realized by prestressed bolt, prestressed cable and shotcrete. After test, anchor cable tension using the traditional anchor cable construction technology can't meet the design requirements, at the same time, it takes about 30 days to achieve prestressed tensioning. Therefore, we need to study the high-performance fast tensioning prestressed anchor cable technology, to effectively control surrounding rock deformation, to ensure the safety of construction, improve construction efficiency. Research conclusions:(1) The traditional anchor cable construction technology is adopted. The anchor cable tension value is mainly controlled by the grip force between the anchor rope and grouting body and the cohesive force between grouting body and surrounding rock. (2) The grip force between the anchor rope and the grouting body can be increased by about 2 times by increasing the "barb"; The cohesive force between the grouting body and the surrounding rock can be increased by 1.5 times by 6 ~ 7 MPa high-pressure grouting process. (3) The modified sulphoaluminate cement slurry can reach more than 30 MPa within 1 day of the slurry strength, so as to realize fast anchor cable tension within 1 day after grouting completion. (4)The research results can be used for reference in similar prestressed anchorage cable construction projects. © 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.     

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.     

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.     

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 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.     

New analysis method of seismic passive earth pressure and its distribution on a retaining wallEI北大核心

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.