多年冻土区铁路保温路基变形特征研究

冻土具有极为特殊的工程地质性质,修建其上的路基将不可避免地发生变形,甚至是破坏。为保证道路畅通,冻土路基在满足热稳定性要求的同时,道路路基的变形也必须满足设计规范要求。基于青藏铁路北麓河保温路基的地温、变形监测资料,分析路基地温、变形特征及其相互关系。研究结果表明,冻土路基的变形和其下地温场状况密切相关,地温场状况及其变化控制和决定着冻土路基变形场的状况。多年冻土地温升高产生的冻土压缩变形是导致保温路基持续较大变形的主要原因之一,在冻土路基变形研究中不可忽略。而冻土融化产生的变形是冻土路基变形的主要因素。基于实际监测数据分析结果,考虑到温度对多年冻土地区土体力学性质的强烈决定作用,建立冻土路基热弹塑性融沉压缩本构模型,进行温度场和变形场的单向耦合分析。计算结果表明,当该地区年平均温度较低、在路基高度较小的情况下,铁路保温路基的变形较小。相反,在该地区年平均温度较高,路基高度也较大的情况下,冻土路基的变形较大,这也和监测结果相符合。

STUDY ON DEFORMATION CHARACTERS OF RAILWAY INSULATED EMBANKMENT IN PERMAFROST REGIONS

Due to special engineering geological characters of the permafrost, it is inevitable for the embankment above the permafrost to come into being deformation, even failure. To ensure the railway unblocked, it is necessary for the embankment in permafrost regions to meet not only the requirement of the thermal stability, but also the requirement of the structure stability. Based on the observation data of the insulated embankment in the Beiluhe test site along the Qinghai--Tibet Railway, the characters of the ground temperature and the deformation of the insulated embankment are analyzed, and the relationship between the ground temperature and the deformation is presented. The observation data indicate that the embankment deformation has close relationships with the ground temperature of the embankment, and is controlled by the ground temperature state and its change. The analytical results also show that the compressive deformation of the permafrost due to ground temperature rising partially results in the durative deformation of the insulated embankment which cannot be ignored. The thaw settlement results in the biggest embankment deformation. According to the analytical results, taking the fact that the permafrost temperature strongly controls the physico-mechanical properties of permafrost into consideration,an embankment deformation model, which considers the factors such as the compressive deformation, the thaw settlement etc., is established. The railway embankment deformations in the coming 50 years are simulated. The computational results indicate that the less embankment height and lower mean annual air temperature result in the smaller embankment deformation. On the contrary, the larger railway embankment deformation will be brought if the railway embankment is high and the area has high average annual air temperature.