Accumulative Settlement Of Saturated Silt Subgrade Under Transportation Cyclic Loading

In recent years, the transport industry is booming, the construction of transport infrastructure is in full swing, and construction achievements of highways and high speed railways grows rapidly. With characteristics of high speed, high traffic density, high security and high comfortable, the railway lines must be in a high smooth state.Un-uniform settlement of the roadbed will lead to irregularities of track system and underline structure, leading to strong vibration in the rack system, which not only brings great harm to the trains-traffic safety, also results in accumulative damage to the railway lines(including rails, sleepers) and lower part of the roadbed (including embankments, underlying layer of foundation). This in turn, the dynamic interaction between the train and the railway line system, which further aggravates the un-uniform settlement of the roadbed.Silt is widely distributed in the alluvial plains, river deltas, coastal plains, especially several large river deltas such as the Yellow River Delta, Hangzhou Bay. A variety of diseases emerge in silt-based transportation infrastructure in long term service, resulting in abnormal service of the rail and road infrastructure. In order to investigate the characteristics of cumulative axial strain of silt soil, study the atenuation process of dynamic modulus under long-term traffic loading, a series of dynamic triaxial tests are conducted on Qiantang River silt soil to study the variation of samples in different physical conditions(relative compaction, water content) under differrent stress levels(frequency, confining pressure, cyclic stress ratio), and reveal the im-pact on the cumulative axial strain, dynamic modulus, damping ratio by these factors, and summarize their variation. Then combine with the model test results of the large-scale physical model test system constructed by institute of geotechnical engineering of Zhejiang University, provide a scientific basis for the calculation and prediction of the accumulative settlement of saturated silty roadbed under traffic cyclic loading.