| With the rapid development of the worldwide high-speed and heavy-duty rail transport, Wheel-rail system dynamic action is growing, the various parts of the track deformation failure significantly accelerated. As a the slab track key structural layer,Emulsified asphalt cement mortar layer mainly play the function of support, cushioning and adjustment, its performance will even determine the success or failure of the slab track.Practice shows that, emulsified asphalt cement mortar with complex material properties is very sensitive to the natural environment and train load. It’s difficult to avoid producing a variety of diseases during their service, and the diseases will affect the track structure and traffic safety.The influence of mortar damage to the track structure and wheel-rail system dynamic performance is unclear now,and also the lack of cement emulsified asphalt mortar maintenance standards. This article is mainly about the research on the damage for low elastic modulus cement emulsified asphalt mortar of frame type slab track, including the following contents and conclusions:(1) Based on field surveys and experimental studies, the form and characteristics of cement emulsified asphalt mortar damage is summarized,and the mortar disease is divided for their own damage, the interface damage and legacy defects three categories. And from the viewpoint of the the mortar microstructure characteristics and environmental adaptability, performance deterioration of the mortar material law is elaborated, and provide a reference to explain the cause and development mechanism of the mortar damage.Studies have shown that, the mortar material is sensitive to the natural environment, The causes and development of the mortar damage or defects is the results of the structural design, material properties, the natural environment, train loads, and construction quality coupling of multiple adverse factors, including temperature and water pressurethe role is one of the important factors leading to the degradation of the material properties of mortar, mortar material environmental adaptability, and improve the quality control of the construction process and optimize the conditions of mortar force is the basic ways to ensure that the mortar to maintain long-term durability.(2) Simplified rational mechanics, using the finite element method, analysis statics model for the frame-type slab track is established, using life and death unit and contact analysis theory,the mortar damage and the relationship between the mortar and track slab is effectively simulated,consider the train load and temperature gradient alone or coupling, in-depth studying the influence of mortar damage of different form and size to track structure.Studies have shown that, the influence of mortar damage to track slab and mortar layer is the most disadvantaged, and the base plate by the force of the impact is relatively small; through static analysis, when the length or deepth of the mortar damage is more than about0.20～0.30meters, the influence of mortar damage to track structure become apparent; when the mortar is completely damaged along the track transverse, while the longitudinal length of mortar damage is about0.80meters, track slab tensile stress may overrun, and the vertical compressive stress of mortar layer is also increasing rapidly, and will accelerate the development of fatigue injury for hurt neighborhood mortar;as one of the main disease forms of slab track, the impact of the mortar damage to track structure is more obvious.(3)A site testing is done about the damage of cement emulsified asphalt mortar for the frame type slab track in Suiyu line, to assess the effect of mortar damage to vertical vibration performance of rail system and the maintenance effects of on-site maintenance.Through site testing, the vertical dynamic response of rail is less affected by the mortar damage, the vertical dynamic response of track slab is more sensitive to the mortar damage; compared to the traffic speed, the impact of train axle load is more obvious, generation of the mortar damage is likely related to the train axle load; while the mortar damage is restored, the supporting on the bottom of track slab can be significantly improved in the short-term, but the durability of the repair material and the bonding interface is still worthy of attention.(4) Based on the dynamics theory of wheel-rail system, with finite element analysis software ANSYS/LS-DYNA, mortar damage is simplified, and a vehicle-frame type slab track vertical coupling vibration space of finite element model is established, and the theoretical calculations and the site testing results were compared to verify the validity of theoretical calculations. in this basis, in-depth studying the influence of mortar damage of different form and size to the vertical dynamic characteristics of track system and traffic safety comfort.Dynamic analysis studies have shown that, the mortar damage will cause partial mutation of track stiffness, form the track dynamic irregularity, intensify the vibration of the wheel-rail system, reduce driving safety and comfort, especially for the type of mortar damage at adjacent slab end, while the slab edges mortar damage is impacted relatively small; as mortar damage in the form of plate end, when the longitudinal length of the mortar damage is more than0.60-0.80meters, the wheel-rail system dynamic action significantly intensified, and the track dynamic irregularity caused by mortar damage began to play a leading role, maximum wheel-rail vertical force, load shedding rate as well as the body, bogie and wheel vertical vibration acceleration increased sharply, and it will accelerate the orbital components trauma, reduce driving safety and comfort; the influence of mortar damage to the track system vibration is significantly higher than that of driving, for example, pulling force on the fastener,the track plate vertical vibration acceleration, mortar dynamic pressure stress, rail and track slab vertical displacement are increased dramatically as the increasing of the longitudinal length of mortar damage, especially when the longitudinal length of the mortar damage exceeds0.60-0.80meters, the various parts of the track dynamic response increased dramatically, while the longitudinal length of the mortar damage at the bottom of the adjacent two slabs is1.538m, it may cause that the pulling force on the fasteners and rail vertical displacement will exceed the limits, and mortar vertically dynamic compressive stress is more than10times of the normal case,showing that mortar damage will highly affect their neighborhood mortar and reduce neighborhood mortar fatigue life. (5) By analyzing the law of the deterioration of the track system, combined with the characteristics of the cement emulsified asphalt mortar damage and the principle of preventive maintenance, based on track structure of static and dynamic theoretical analysis, and from the angle of the mortar fatigue life, the maintenance level and criterion of cement emulsified asphalt mortar for framework-type slab track is initially proposed.The study showed that the mortar fatigue life is mainly affected by temperature and mortar stress; cement emulsified asphalt mortar maintenance level is divided into grade I, grade II and grade III three levels, according to the theoretical analysis and practical experience, and then developed a different level and the criterion of emulsified asphalt cement mortar damage. |
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