Study On The Subgrade Long-term Cumulative Deformation Damage Characteristic Induced By Heavy-haul Train Load

Since the reform and opening up, with the development of china’s economy, theconstruction of railway is also developing rapidly. Especially in recent years, with theincreasing demand for resources in various regions, heavy haul railway has become thedevelopment trend of our country’s railway freight. Heavy haul railway has thecharacteristics of heavy axle load, huge transportation capacity and big traffic density,which exacerbated the subgrade deformation, subsidence, boiling, damage, stability andother diseases. These directly concern the safety of railway transportation and thedevelopment of national economy.Aiming at studying how heavy traffic loads affect subgrade damage, the presentthesis studies on the dynamic performance of thawing soil, the vibration response anddamage property of subgrade induced by long-term traffic loads, using methodscombined experiment in laboratory and numerical simulation. The main researchcontents are presented in detail as follows:(1) Based on indoor room temperature dynamic tiaxial texts, research the variationof dynamic modulus and damping ratio of thawing soil with the change of confiningpressure, load frequency, moisture, freezing-thawing cycles and other factors, and therelationship between cumulative plastic deformation and times of vibration of thawingsoil under traffic loads.(2) According to the actual construction points of heavy haul railway, by taking thesystem of railway sleeper-ballast-subgrade-site as the research object, build atwo-dimensional finite element model, then study the variation of dynamic stress ofsubgrade along transverse and vertical location and analyze the influence of train axleload and train speed on subgrade dynamic stress.(3) Based on the hypothesis of Palmgren-Miner linear cumulative damage, get therelationship curve between the critical vibration times, dynamic stress and comfiningpressure by fitting data, and get the calculation method for subgrade damage. Accordingto the dynamic stress and static stress getting from numerical models in chapter3, getthe relation between subgrade damage value and vibration times under differentworking conditions, research the variation of damage value along the depth of subgrade,and explore the influence of train speed and train axle load on subgrade damage property.