Abstract：Hanjialing Mountain Tunnel is a key engineering in reconstructing the expressway from Shenyang to Dalian，and it is a highway tunnel with the greatest across span of arch in Asia. The tunnel consists of a single tube with four lanes，and was excavated with the layer-step method，which is a new attempt in constructing the tunnel with large across span. In order to clarify the mechanical behavior in the process of digging the large span tunnel and provide the technological data for design and construction，the research of stability stress monitoring for Hanjialing Mountain Tunnel is performed. In this paper，it expresses mainly the method adopted for monitoring the stress of tunnel structure，and analyzes the data of touch stress changing with time between shotcrete lining and surrounding rock，as well as the change of internal force of rock bolt. The research results show：(1) because the width，height and space of digging tunnel is large and the touch stress measured between surrounding rock and shotcrete lining is small，for the initial supporting structure，shotcrete lining and rock bolts only act as cooperation and auxiliary on resisting the deformation of rock，but main support action can be result from the steel arch frame and the bearing ability of rock itself. The greatest touch stress is 0.097 MPa，the largest axial force of bolt 4.73 kN. (2) after reaching the peak value，the touch stress of shotcrete lining and the axial force of bolt are still wavy to a certain extent. Although it will not affect the stability of tunnel with the progress of dig engineering，the loading action on the initial supporting lining from surrounding rock deformation is in a change state. (3) for the measured section of tunnel，on the side in which the surrounding rock is stable，the touch stress is tensile between the surrounding rock and the shotcrete lining，on the other side，the surrounding rock is unsteady. The touch stress is compressive，so it expresses that the horizontal displacement of this across section originate mainly from the side of unsteady rock. (4) the way of layer-step constructing is feasible for large span highway tunnels，by means of short driving and short supporting，so that the ground pressure can be released and the surrounding rock displacement can also be controlled.
