Study On The Dynamic Characteristics And Design Methods Of Subgrade Of Heavy Haul Railway

As the continuous development of heavy haul railway, the train axle load enlarged and speeded up, which made new requirements for the design of the subgrade bed structure.Based on elasticity theory, ABAQUS was applied to build up pathway-roadbed finite element model and make analysis of overloaded railway bed structure load condition and roadbed dynamic characteristics. Overloaded railway subgrade bed thickness under different axle load was established by dynamic strength design index. The work mainly includes the following aspects:Overloaded railway embankment load conditions were studied. Results indicate that number of roadbed sleeper bear, load sharing ratio will not change with the size of the whee l axle load, bed surface differences in packing.Under the single shaft load, most of the load borne by 5 root sleeper. Load sharing ratio was 9.8%:23.3%: 33.3%:23.3%:9.8%. Under double shaft load, most load borne by eight root sleeper. Load sharing ratio was 8.82%:22.52%:35.45%:32.22%:31.87%: 35.67%:23.83%:9.60%.Under four axles load, most of the load borne by 15 root sleeper. Load sharing ratio was 8.86%:22.47%:35.11%:31.36%:30.76%:35.93%:29.47%:27.05%:34.40%: 33.25% :30.04%:34.87%:29.02%:13.81%:3.72%.Analysis of dynamic behavior of overloaded railway subgrade bed was made. It turned out that,dynamic stress of multi-axle load become bigger,compared with single shaft load under the same condition. Maximum dynamic stress of double shaft or four axles load was significantly greater than maximum dynamic stress of single shaft load on the base of bed surface. Stack effect will increase the dynamic stress. Difference between maximum dynamic stress of double shaft and four axles load was not big. With depth increase, superposition effect of four axles was more apparent and dynamic stress attenuation speed slowed down obviously, whose range of influence on the depths of the bed was obviously bigger.Comparative analysis of results of the finite element calculat ion and information in railway standards was made. The results show that, dynamic stress of bed bottom was about 13.49%—19.49% gravity stress of the soil, meeting the principle of dynamic stress is 0.2 times gravity stress in standards. While under double shaft load, dynamic stress of bed bottom was about 26.7%—34.55% gravity stress of the soil and four axles load 42.15%—51.54%, which far more than the specified value that dynamic stress is 0.2 times gravity stress. According to the specification, whole bed thickness is about 4.5m under 25 tons of axle load, 5m under 30 tons and 5.5m under 35 tons. Under the duplicate effect of multi-axles, the dynamic stress amplitude and range of influence grow greatly,which does not meet the requirements of specificatio n.Dynamic strength of bed of the different packing was established combining with a large collection of test data. Design thickness of surface and underlying of the bed under different axle loads was calculated by finite element software, based on the cri tical dynamic stress control criterion. The results show that,Bottom layer of foundation bed will not change greatly formation base layer. Whole bed thickness of different bed surface layer thickness has no big difference. Whole bed thickness under 25 tons of axle load is 2-2.3m, 2.8-2.9m under 25 tons and 3.2-3.3m under 25 tons.