| High-speed railway,because of its advantages about fast speed, large volume, low energy consumption, safety and reliability, is gradually being highly valued by governments around the world and get good graces from passengers. In order to ensure the stable and high-speed of the high speed railway line for passenger transport, and avoid the safety hazard caused by the irregularity of the railway transportation, the post-construction settlement of foundations is controlled within the 15 mm by specifications. The existing method for evaluating post-construction settlement is curve fitting method, which is mostly based on the saturated soil theory. But most of the railways were built in the unsaturated areas, these make that predict the post-construction settlement of unsaturated areas with saturated soil theory need further research. It is attracting more and more attention of researchers for the difference of the law of settlement between unsaturated soil and saturated soil. Thus, there is more application to study the predictive model based on the saturated soil theory and analyze the settlement of high-speed railway foundation.Inverse "S" type settlement prediction model can accurately predict the settlement of different regions of saturation, which is based on unsaturated soil theory and proposed by Jiang Chuang. But the meaning of parameters are not clear, the application is poor, and fail to provide effective guidance for high speed railway construction in time. Therefore, it is very important to define the parameters of the model, which make high-speed railway construction more scientific and standardized.This paper summed the deformation of high-speed railway in unsaturated areas, which is based on the analysis of settlement monitoring of three high-speed railway, and determined the meaning of each parameter appeared in the prediction model for unsaturated settlement which is conducted a laboratory tests. Furthermore, it is great significance to the scientific and standardized construction of high-speed railway.The contents and results of this paper are as follows:(1)The obvious differences of settlement between unsaturated foundation and saturated foundation will be revealed with the spot data. That is, the immediate settlement appeared in low saturation area, the settlement-time curve showed a broken-line type and long consolidation time, slowly increasing of settlement in high saturation area.(2)The influence of matrix suction and dry density on the consolidation characteristics of unsaturated soil is studied by using the unsaturated consolidation apparatus and the GDS system. The results show that suction has a great influence on the settlement curve, when the matrix suction lower, the consolidation time is shorter, then there is a significantly increase with increasing matrix suction, but if the matrix suction continues to increase, the consolidation time will be gradually reduced, and when the matrix suction achieve a great value, the consolidation will be completed at a faster rate. However, it is found that the dry density has no obvious effect on the time curve of unsaturated soil.(3)The experimental data and the parameters of prediction model for unsaturated settlement are fitted. The results show that the change of saturation has a slight influence on the a and n when the saturation is low, with a value is small, and as the saturation comes to a higher value, a and n will be increased with the increasing saturation.(4)The model is used to predict the foundation settlement in unsaturated areas. And the correlation is found to be good compared with the measured data, which verified the application of model and the accuracy of parameter variation. |
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