The largest resultant deformation value (13 mm) was measured in the sandstone–shale alternation between chainage 500 and 550 m, which was highly weathered by groundwater and affected by local tectonic disturbance. The smallest deformation value was observed in a stiff dolerite dyke between 370 and 430 m, where at times the deformation values decreased to zero. In the sandstone, small resultant deformation values (2–4 mm) were also recorded. The 500–550-m interval of tunnel alignment had the highest risk for tunnel instability in the studied section but the deformation values (maximum 13 mm) were within the tolerable deformation range (10 cm). Small negative longitudinal deformation values decreasing between chainage 320 and 370 m and small positive longitudinal deformation values decreasing between 420 and 480 m indicate the sandstone–shale alternation (weak rock) and the dyke (stiff rock) and sandstone (stiff rock), and the sandstone–shale alternation with a fault gauge zone (weak rock), respectively. These longitudinal deformations needed probable to predict the lithological transitions ahead of the face, which in timely were used to determination of the tunnel support system. 相似文献