青藏铁路冻土路基沉降变形预测

Estimation on the Settlement and Deformation of Embankment along Qinghai—Tibet Railway in Permafrost Regions

青藏铁路试验工程北麓河试验段冻土路基沉降变形现场试验研究表明:即使路基下冻土人为上限有所上升,冻土路基仍会产生较大的沉降变形。这种变形主要来自原天然上限以下高温—高含冰量冻土升温引起的压缩变形。路基下多年冻土的升温幅度、高含冰量冻土层厚度和路堤高度越大,路基的沉降变形量就越大。数值计算结果表明:在路堤填土满足临界高度,且考虑青藏高原年平均气温逐年上升的条件下,青藏铁路北麓河试验段冻土路基在未来50年内的总沉降量可能达到30 cm。因此,要控制冻土路基的沉降变形,必须采取主动降低多年冻土温度的工程措施,单纯靠增加路堤高度的传统方法不能解决问题,甚至适得其反。

According to the in-situ experiment results of embankment settlement and deformation at Beiluhe test site along Qinghai-Tibet Railway in permafrost regions, it was found that, even though the permafrost table under the embankment moved up after the railway was built, the embankment has suffered quite a lot of settlement, and the settlement was mainly from the compression of the warm and ice-rich fro- zen soils under the original permafrost table caused by increasing the temperature of the permafrost. The greater is the increase of temperature, the thickness of ice-rich permafrost and the height of embankment, the more the settlement of embankment will be. Numerical calculation indicates that, even if the thickness of the filled soil meets the critical height, the settlement of the railway embankment at Beiluhe test site in permafrost regions will reach the value of 30 cm in the coming 50 years against the annual average temperature increase year after year on the Qinghai-Tibetan Plateau. Therefore, if the settlement of embankment is to be controlled, the active cooling measures must be taken to lower the ground temperature under the embankment. The traditional method to raise the height of the embankment is ineffective and even worse for the stability of the railway subgrade in permafrost regions.