高速铁路路基动力累积变形模型试验研究

The model test of dynamic accumulative deformation of high-speed railway track foundation

以中南大学高速铁路无砟轨道路基足尺模型试验系统为背景,对Ⅲ型板式无砟轨道在列车轴重为17 t,速度为350 km/h条件下开展10000万轴次循环荷载试验,以研究路基在高速列车长期荷载作用下的动力累积变形规律。研究结果表明:随着列车轴次的增加,路基累积变形逐渐增加,在循环加载前期增长速率较快,之后逐渐减小,在列车轴次达到350万次后趋于稳定,路基最终累积变形为3.38 mm,其中基床表层、基床底层、路基本体和地基各结构层最终变形分别为2.33,0.57,0.30和0.18 mm。基床表层变形最大,占总累积变形的68.93%,基床底层次之。通过对指数模型在路基模型试验中的适用性进行分析,结果表明路基各结构层累积变形采用指数模型拟合的效果较好,相关系数均在0.985以上。基于试验结果,提出一个以动静应力比、静应力与静强度比、振次为基数的指数模型,依据试验结果对模型参数进行反分析,得出模型中各参数变化范围较小,修正模型改进效果非常明显,可以用于预测长期动力荷载作用下高速铁路路基累积变形和路基沉降。

Based on the full-scale model test system of high-speed railway ballastless track foundation housed at Central South University,the CRTS III slab track was subjected to cyclic loading with up to 100 million repetitions to simulate the application of train axle load of 17 tons traveling at the speed of 350 km/h.The dynamic cumulative deformation characteristics under the long-term loading of high-speed train were studied.The results show that as the number of axle load applications increases,the cumulative deformation of track foundation increases gradually.The growth rate of the cumulative deformation is greater in the early stage of cyclic loading and then decreases gradually.After the number of axle load applications reaches 3.5 million,it tends to be stable.The final cumulative deformation of track foundation is 3.38 mm,and the final deformation values of surface layer,bottom layer,main body of subgrade and natural subgrade are 2.33,0.57,0.30 and 0.18 mm respectively.The deformation of the surface layer of track foundation is the largest,accounting for 68.93%of the total accumulated deformation,followed by that of the bottom layer of track foundation.Through the analysis of the applicability of the exponential model in the full-scale model test,the results show that the cumulative deformation of each structural layer of track foundation can be well fitted by the exponential model,and the correlation coefficient is greater than 0.985.Based on the test results,the exponential model incorporating the ratio of dynamic to static stress,the ratio of static stress to static strength,and the number of load applications was proposed.According to the test results,the parameters of the model were back calculated.It was concluded that the changing range of the model parameters is small,and that the efficacy of the modified model is very obvious.This model can be used to predict the cumulative deformation and settlement of high-speed railway track foundation under long-term dynamic loading.