Objectives Geological disasters in mountain areas are directly related to the construction and operation effect of expressways. How to find and identify major potential hazard sources in advance and take corresponding measures has become the focus and difficulty of highway route selection in mountainous areas.

Methods Multilevel investigation and analysis of geological hazards in Xinchanggou section of G4216 expressway are carried out by using multi-technology, and the corresponding suggestions for route optimization are given. First, multi-temporal high-precision optical remote sensing images are used to interpret and analyze the hidden geological hazards within the planned route in the research process. Second, small baseline subsets interferometric synthetic aperture radar (InSAR) are used to quantitatively detect and evaluate the surface deformation in the key areas affecting the route direction. Finally, the airborne light detection and ranging (LiDAR) technology is used to conduct detailed exploration of areas with high risk of geological hazards.

Results Optical remote sensing consensus identified 40 hidden geological hazards, 10 of which have different degrees of threat to the construction of expressways. InSAR technology was used to detect a total of 13 hidden points of sliding bodies with obvious deformation, among which a giant deformed body was found on the left bank of Xinchanggou, which directly threatened the direction of the planned route. On this basis, it was found that the middle part of the deformed body showed signs of pulling cracks through the LiDAR technology and field investigation, and the upper part of the deformed body showed ladder dislocation, and the deformation signs were obvious, which should be avoided. The results show that the combination of the above means can detect the hidden dangers of geological disasters to the maximum extent at great speed.

Conclusions The safe circumvention scheme of expressway route is given, which promotes the transformation of expressway route selection technology from extensive to refined. It is of great reference significance and value to highway route selection.