Hierarchical object method of highway route selection in permafrost region

In order to design the highway route in permafrost region, the hierarchical object method to protect the permafrost from coarse to fine, from surface to belt, from band to line was proposed based on multi-scale effect theory, and the theory model was constructed. Combined with the display forms of different topographies, landforms, existing projects, structures, and buildings in different scales, the hierarchical division of hierarchical object method was given, and the influence factors of highway route selection in each level were determined. Considering the influence of route node's importance degree, topography and landform in permafrost region, the highway route selection model in the first level was given. The scale classifications of average altitude, average slope, annual average ground temperature, permafrost distribution, talik structure, and existing projects were obtained by using commensurability principle, and then thehighway route selection difficulty degree model in permafrost region was established in the second level. The permafrost hazards caused by permafrost ground temperature, permafrost ice content, permafrost disaster, and vegetation coverage were considered synthetically, and the thermal disturbance among existing projects in permafrost region was also taken into consideration, then the highway route selection reliability model in the third level was established. The permafrost region of Qinghai-Tibet Plateau from Xiushui River to Yamarle River was taken as example, and the route selection was carried out by using hierarchical object method. Analysis result shows that the route plan determined by hierarchical object method can accurately avoid the permafrost region with high disease rate and evade the disturbance among existing projects, and a route plan with low engineering difficulty degree and high engineering reliability is achieved.