Research On The Deformation And Strengthening Measures Of Subgrade In Bridge-Subgrade Transition Section Of Existing Heavy Haul Railway

High-speed passenger line and heavy haul railway are two major trends in the development of world railway, and heavy haul freight transport has become an important symbol of modern railway freight transport. With the increase of axle load and the train speed, dynamic interaction of train-track system becomes so exacerbated that the deformation and dynamic response of subgrade are more aggravated. The differential settlement will be created in bridge-subgrade transition section under such dynamic action, and an adverse effect on the train operation safety can be caused. Meanwhile, differential settlement will produce additional dynamic effect on the lines when high-speed trains go through the railway lines. Such dynamic action will intensify the deterioration of settlement and accelerate the damage of subgrade. Moreover, the bridge-subgrade transition section has lower design standard and the quality of subgrade can't meet the requirements for historical reasons.Therefore, it is of great significance to put wheel-rail system and subgrade system into the whole system in analysis. It is also of application value to establish appropriate model for various calculations to sum up the deformation and dynamic response laws of subgrade in transition section. Meanwhile, to study on strengthening measures of subgrade and existing bridge-subgrade transition section also has important practical significance for the preservation of track geometry and assurance of train operation safety.Based on the above analysis, this dissertation, via research projects "Research on strengthening subgrade and track of bridge-subgrade transition section in existing line", applying the methods of theoretical analysis, field test, numerical simulation, etc. to systematically study the deformation and dynamic response characteristics of subgrade in bridge-subgrade transition section of heavy haul railway under static and dynamic load for the first time. And the dynamic response characteristics of two and three dimensional longitudinal model of bridge-subgrade transition section are studied intensively in this dissertation. The subgrade quality inspection and strengthening measures are also studied. The main research work and accomplishment of this dissertation can be generalized as follows.(1) The engineering geological conditions of Shuohuang railway are introduced firstly. Then a detailed research is done on subgrade quality inspection and geometry size at the scene of the transition section. The basic parameters of the transition section is obtained to provide a basis for further analysis of the deformation and dynamic response characteristics of subgrade in bridge-subgrade transition section.(2) The deformation of subgrade of bridge-subgrade transition section under static load is simulated by using ANSYS FE software with focus on the influence of changes of the parameters on the deformation of the embankment.(3) The train-track-subgrade vertical vibration system model is established to analyze the dynamic response of model under train load. Then the dynamic stress form in the subgrade surface is given in ANSYS analysis.(4) The dynamic response of transverse and longitudinal model of subgrade in bridge-subgrade transition section are studied respectively under moving load to study the influence of surface layer stiffness of bed, stiffness and density of filled soil of the transition section on subgrade and change law of vertical dynamic stress. Further analysis of the influence on the different axle load, train speed, filled soil modulus, etc. factors on the dynamic response of the embankment are carried out after that.(5) 3-D finite element analysis of the dynamic response of subgrade in bridge-subgrade transition section under the conditions of the train's getting on and off bridge and two trains' running in both directions is carried out respectively to simulate Shuohuang field test in two-lane conditions. And the transverse and longitudinal 3-D dynamic response laws under the three conditions of subgrade are summed up systematically.(6) The strengthening scope and measures of subgrade in bridge-subgrade transition section are studied based on the field tests results and numerical calculation conclusions. The strengthening scope and measures to do in field transition section are discussed at the end.