Abstract: The loess tunnel excavation is always a difficulty in the field of construction. The construction risks of Dikengyuan Tunnel crossing the geological terrain along the line are analyzed, the deformation laws of the primary support of typical cross-sections and longitudinal sections are studied based on the monitoring and measurement data, and the temporal and spatial characteristics of primary support are obtained. The analytical results show that: (1) The surrounding rock deformation is characterized by long duration and high speed, and sometimes with abrupt variation.
(2) The cross-section of the primary support is unevenly converged, and the longitudinal deformation is directly related to the distance from the chosen section to the tunnel face. (3) The tunnel deformation is greatly affected by terrain, groundwater and construction. Some relevant control measures are purposed according to the large deformation laws of the surrounding rock on the site. The research results can provide technical guidance for the site construction.

Key words: loess tunnel, unsymmetrical pressure, large deformation, monitoring measurement, deformation treatment