Advanced Materials Research Vols. 255-260

Abstract: The values of longitudinal horizontal linear-stiffness of piers are very important parameters in the design of welded turnout on bridge and they can have a great impact on the force and displacement of the turnout. The layout form of turnout and bridge of welded turnout structure system on high-speed railway bridges are various, so the values of longitudinal horizontal linear-stiffness of piers have to be limited in order to insure the strength and stability of track structure on bridges and at the same time meet the requirement of comparative displacement of beam and rail, turnout proper and frog. To make the value-taking easy in the design process, a finite element model for welded turnout-bridge-platform is established in this paper, which is based on the principle of longitudinal interaction of welded turnout on bridges. Directing at three typical layout forms (No.18 single turnout+4×32m continuous beam, single crossover+6×32m continuous beam and typical throat point+4×32m continuous beam) of welded turnout and bridge on ballast track, a research of the relation between the force and displacement of turnout, and the values of longitudinal horizontal linear-stiffness of piers has been carried out. Based on the comprehensive analysis, minimal values of longitudinal horizontal linear-stiffness of piers which are suitable for these three kinds of layout forms, and the values are 1000,800 and 1600 kN/cm·double-line respectively.

Abstract: The thermodynamic model which quantificationally described the behavior of cerium in heavy rail steel was proposed. From the model, the effects of cerium on the composition, sequence and transformation condition of inclusions and the content of cerium dissolved in heavy rail steel were studied principally. When the cleanliness of heavy rail steel is low, the sequence of inclusions precipitation in heavy rail steel is Ce₂O₃, Ce₂O₂S, Ce₂S₃ and CeS. With increasing the cleanliness of steel, the sequence of inclusions precipitation is Ce₂O₂S and CeS. At 1783 K, the necessary condition of Ce₂O₃ precipitation in heavy rail steel is a_o/a_s≥0.186, for Ce₂S₃ precipitation is a_o/a_s≤0.394. The content of cerium dissolved in heavy rail steel is mainly affected by Ce₂S₃ inclusion. With the precipitations of all inclusions being stable, the curve between the dissolved cerium content and cerium addition becomes linear.

Abstract: Train/turnout dynamic interaction is exacerbated by high speed of passenger train and heavy load of freight train, and wheel/rail relation is one of the key factors that determine the running characteristics of the train. Focusing on three types of wheel treads with different profiles (TB tapered tread, LM worn tread, LMA worn tread), longitudinal distribution of the contact geometric parameters along the switch rail and nose rail of 350km/h No.18 turnout are calculated, such as tread equivalent conicity, coefficient of contact angle difference, roll angle factor, gravitational stiffness of wheelset, gravitational angle stiffness of wheelset, etc. Results show that: (1) LMA worn tread produces the smallest irregularity; (2) wheel/rail vertical impact at the frog will become bigger; (3) Top profile of switch rail and nose rail should be designed according to the wheel tread type so as to mitigate the wheel/rail dynamic interaction and increase the safety and stability of a train.

Abstract: Considering adverse effects of shallow gas geology on Hangzhou Metro construction, based on the fluid-solid coupling analytical method of multi-phase media, effects of shallow gas on diaphragm wall trenching construction were examined by using FLAC-2D software. In combination with the diaphragm works of a typical subway station in the region buried shallow gas, the deformation on slurry trench of diaphragm wall were analyzed under working conditions using different specific gravity slurry. Results show that shallow gas escape of the stratum significantly affects stability of the groove wall, easily leading to collapse of the soil and resulting in the concrete diaphragm wall with quality problems such as honeycomb, reducing diameter, bulging, breaking zone and etc. In trenching construction of the diaphragm wall, increasing the specific gravity of slurry appropriately is an effective way to reduce adverse effects of the shallow gas, but it should not be too large. A suitable range of mud weight varies from 1.06 to 1.10.

Abstract: To improve the calculation precision of deformation in prestressed concrete bridge in passenger dedicated line and accurately predict the development of shrinkage and creep in bridge, a universal applicable modified model was put forward in this paper based on ACI 209R(1992) shrinkage and creep model. In the modified model, three influence factors-slump, strength and reinforcement - are corrected. And the modified model results were compared with the experimental results. It shows that the modified model can more accurately predict the development of shrinkage and creep of high-speed railway bridge and better accord with the law of it.

Abstract: The Chaidaer-muli railway winds along the Datong River in the central region of the Qilian Mountains. The widely distributed permafrost along the railway is characterized by swampy and warm, which leads to the poor Engineering geologic conditions of the transportation line from the point of frozen soil. That the extending direction of the railway is nearly southeast-northwest causes its roadbed experience the yin-yang slope problems. To improve the stability of frozen soil roadbed, proactive cooling measures were adopted in a large proportion of the roadbed with permafrost, in which about 20km railway was equipped with thermosyphon. At the same time, different design parameter was adopted in the sunny and shady side slopes in the thermosyphon parts. Observation data in the experimental section with warm permafrost shows, under the condition of current thermosyphon techniques and design parameters, thermosyphon measures can effectively cool the frozen soil roadbed, substantially reduce the settlement and successfully solve the yin-yang slope problem of the railway subgrade in swampy warm permafrost.

Abstract: Based on the contrast of survey method in existing railway, considering the actual situation on site, nuclear densimeter, E_vd and light dynamic penetration methods were used in survey, and then analyze influencing factors of survey results in existing railway. Since there is no mathematical statistics method for survey evaluation in existing railway, taking "Quality inspection and evaluation standards for highway engineering" as reference, evaluation standard for existing railway at 200km/h was proposed. Filling materials segment method, task segment method and enforcement segment method were used for the evaluation in Ning-Qi existing railway, the road sections length that need reinforcement was reduced, which achieves good effect.

Abstract: This paper studies relationship between soil-cement parameters and unconfined compressive strength. The research in tensile strength and deformation modulus of soil-cement is an important basis for soil-cement failure mechanism and intensity theory. They also impact cracks, deformation and durability of cement-soil structure. Shear strength and deformation of soil-cement is important to the destruction analysis and finite element calculations. Therefore it needs to study on tensile strength, shear strength and deformation modulus of soil-cement. Based on previous experiments, the relationship of tensile strength, shear strength, deformation modulus and unconfined compressive strength of soil-cement are quantitatively studied.

Abstract: The mechanism of train derailment is demonstrated to be the loss of the lateral vibration stability of train-bridge (track) system. Based on the theory of energy increment analysis for system movement stability, the method of stability analysis of lateral vibration for train-bridge (track) system and the energy increment criterion for derailment evaluation are put forward. The method of analyzing critical speed of train derailment is proposed on the basis of the energy increment criterion for derailment evaluation. The critical speed of freight train derailment on Youshui bridge and Laoluanhe bridge are calculated as 66.5 km/h and 65.2 km/h respectively, which are close to actual derailment speed 70 km/h. It is manifested that the method of stability analysis of lateral vibration for train-bridge (track) system is reasonable. The critical speed of train derailment on the Yanconggou bridge of Jingtong line are calculated as 73.0 km/h, and the results has provided important reference for operation department to take appropriate measures.

Abstract: Slab Track, as all railway structures, should provide secure train running and smooth passenger ride. Moreover, it should present sufficient vertical elasticity to distribute the loads to the adjacent fixing points of the rail. At the same time the deflection of the slab track should be comparable to that of the ballasted track which implies a decrease of the value of the acting forces during its Life-Cycle. In this paper the influence of the vertical stiffness of the track on the dimensioning of the slab track as a rigid pavement is presented.