共玉高速公路路基下伏多年冻土时空演变特征及影响因素

Spatio-temporal Evolution Characteristics and Influencing Factors of Permafrost Underlying Gonghe-Yushu Expressway Subgrade

为分析青藏高原高速公路路基下伏多年冻土的时空演变特征,并探讨新建路基路面结构和自然环境因素对路基下伏多年冻土退化的影响程度,以共玉高速公路穿越多年冻土区南界段为例,利用ArcGIS栅格单元属性分析方法对研究区内公开的气候、地形及钻芯数据进行深入挖掘;分析了不同高程、坡度、坡向、归一化植被指数(NDVI)、年平均气温(MAT)、年平均地温(MAGT)、平均年降雨量(MAP)、年平均湿度(MAH)和新建路基路面结构对高速公路路基下伏多年冻土时空演变特征的影响。结果表明:新建路基路面结构对路基下伏多年冻土退化的影响程度为自然环境因素的1.23倍;2011—2019年沿线多年冻土退化呈现出一定的空间异质性,在多年冻土快速和低速退化区内,影响多年冻土退化速度的主要因素分别为MAGT和MAH;影响整个研究区多年冻土退化速度的主要因素为MAGT;2011—2019年高速公路路基下伏多年冻土退化速度为36 cm/a,分别为同期青藏铁路和青藏公路的8倍和2.32倍,为同期同区位G214共玉高速公路的1.83倍。建议青藏高原多年冻土区高速公路选线按无多年冻土分布、有多年冻土赋存的高海拔阴坡、低海拔阴坡、高海拔阳坡和低海拔阳坡的位置分布依次选择,且当路线走向定于后3种情形时,需对路基采取相应的保护冻土措施。

To analyze the spatio-temporal evolution characteristics of permafrost underlying expressway subgrade on the Qinghai-Tibetan Plateau,and to explore the influencing degree of new roadbed pavement structure and natural environmental factors on the degradation of subgrade permafrost,the study took the southern boundary section of Gonghe-Yushu expressway crossing permafrost area for an example.ArcGIS was utilized to conduct in-depth excavation on the publicly available climatic,topographic,and drill-core data in the study area to analyze the influence of different elevations,slopes,slope orientations,normalized vegetation index(NDVI),mean annual temperature(MAT),mean annual ground temperature(MAGT),mean annual precipitation(MAP),mean annual humidity(MAH) and new roadbed pavement structure on the spatio-temporal evolution characteristics of permafrost underlying expressway subgrade.The result indicates that the influencing degree of new roadbed pavement structures on the degradation of perennial permafrost underlying roadbed is 1.23 times greater than that of natural environmental factors.The permafrost degradation along the route from 2011 to 2019 shows some spatial heterogeneity.The main factors affecting permafrost degradation rate in permafrost fast and low degradation zones are MAGT and MAH respectively.The main factor affecting permafrost degradation rate in the whole study area is MAGT.The perennial permafrost degradation rate of expressway subgrade from 2011 to 2019 is 36 cm/a,which is 8 times and 2.32 times of Qinghai-Tibet railway and Qinghai-Tibet highway respectively,and 1.83 times of G214 Gonghe-Yushu expressway in the same area and during the same period.It is suggested that the expressway alignment in the permafrost area of Qinghai-Tibet Plateau should be selected according to the positional distribution of no permafrost distribution,high altitude negative slope with permafrost endowment,low altitude negative slope,high altitude sunny slope,and low altitude sunny slope.When the route direction is set to the latter 3 cases,the subgrade needs to be taken corresponding of permafrost protection measures.