青藏公路低温多年冻土温度的多时间尺度分析

Multi-time scale analysis of the permafrost temperatures along the Qinghai-Tibet Highway

利用小波变换分析方法,对青藏公路风火山监测场地天然状态下和路基中心下15 a的低温多年冻土温度时间序列进行了多时间尺度分析和趋势预测.结果表明:天然地表和路基下部多年冻土温度变化具有多时间尺度特征,二者多时间尺度周期的时频分布特征存在较大差别.天然地表具有简单的规律性,路基中心的规律相对较复杂,主要体现在冻土上限附近.天然地表下当前均处于暖期,深层主要受气候长周期波动控制,使其在进入冷暖期的时间上滞后于上层;路基中心下浅层和深层的冷暖期相反,浅层处于暖期,深层处于冷期,其长度随热交换量大小和热量积累的变化也不统一,给路基的稳定性带来了更大的隐患,但也为控制、减少和治理冻土路基中的病害提供了新依据.

By using wavelet transformation, multi-time scale characteristics and changmg trend of the temperatures within the original ground and embankment in permafrost region at the Fenghuoshan monitoring site along the Qinghai-Tibet Highway are analyzed and predicted. The results show that permafrost temperatures within the original ground and embankment have multi-time scale characteristics, with different time-frequency distributions of multi-time scale; within the natural ground there is a simple regularity; within the embankment there is relatively complex situation, especially, near the permafrost table. Now permafrost temperatures within the original ground are in warm period, and deep permafrost temperatures enters cold-warm period lag behind that in shallow layers. The cold-warm period of shallow and deep permafrost temperatures is the opposite below the embankment, the length of cold-warm period is also not uniform. This could bring more hidden troubles to the stability of roadbed, but provide a new basis for treatment roadbed disease.