Research On Wetting Dynamic Characteristics Of Heavy Haul-railways Subgrade

Due to the increase of operation time of existing heavy haul-railways, theimprovement of axle-load and transport capacity, and the effects of rainfall orunderground water, subgrade diseases happen from time to time, such asmud-pumping, uneven subgrade subsidence and etc., which seriously impact thefeasibility and security of capacity expansion of heavy-haul railways. Consequently, itbecomes critical and urgent to research the subgrade diseases mechanism of heavyhaul-railways.Relying on the science and technology research and development project ofMinistry of Railways Research on Critical Technology of Heavy Axle-load TrainsRunning on Existing Railways Subgrade and Tunnel Test and ImprovementTechnology Research under Technologies of Heavy Axle-load Trains Running onExisting Railways（2012G011-B）, and based on the on-site dynamic tests ofsubgrades, and indoor dynamic triaxial experiments, this paper aims to research thefeasibility and risk level of capacity expansion of heavy haul-railways subgradesunder the immersion effect. Main research contents and results are summarized in thefollowing aspects:(1) Based on Comprehensive R&D Experiments of Critical Technology andEquipment of Heavy Axle-load Coal Transport Heavy-haul Railways, subgradesdynamic tests studied that the impacts of axle-load increase and speed increase ofheavy-haul trains on dynamic stress, maximum acceleration and dynamicdisplacement of subgrade. Test results indicate that, all varieties of dynamic stressesin the surface of subgrade foundation bed basically shows a linear increase as theincrease of axle-load, and change in a wave form as the increase of speed; maximumacceleration and dynamic displacement both increase as the increase of axle-load andspeed.(2)In order to study the security and risk degree of capacity expansion ofexisting heavy-haul railways subgrade under the effect of water, shearing wetting tests, dynamic wetting tests, gradation loading tests, and dynamic intensity tests areseparately performed on subgrade soil body indoor. Shearing wetting tests indicatethat moisture content has a great impact on the intensity index of soil body (c and), and the compactness increase could effectively decrease the wetting deformationof soil body; dynamic wetting tests indicate that the accumulative deformation of soilbody increase as the increase of dynamic stress, and the compactness increase couldeffectively decrease the wetting deformation of soil body; the gradation loading testsindicate that the accumulative deformation of soil body increase linearly as theincrease of dynamic stress, and elastic deformation law is similar to plasticdeformation law; dynamic intensity tests indicate that moisture content andcompactness have a bigger impact on subgrade dynamic intensity.(3) In order to study the impact rule of train axle-load increase on subgrademoisture migration and accumulative deformation, dynamic triaxial tests in theimmersion process are performed indoor. The tests indicate that the immersion effecthas a bigger impact on the accumulative deformation of subgrade; and moisturemigration speed decreases as the increases of dynamic stress and compactness.