Analysis of Deformation of Segmental Lining during Shield Tunneling Based on Real-Time Monitoring

The deformation of segmental lining is an important factor to evaluate the state of tunnel structure. In order to judge the mechanical condition of tunnel structure during construction, a wireless sensor network (WSN) is applied to monitor the tilt change and diameter convergence of 2 sections of a constructing Shanghai Metro tunnel. 4 tilt nodes and 1 distance laser nodes are installed on each section right after the erection to monitor the tilt change of standard segments, adjacent segments and the horizontal of the segmental rings with frequency of 10mins. When the segments are inside the shield tail, the laser nodes are blocked by the shield equipment and workers, unable to monitor the diameter. In order to get the diameter during this period, an ensemble machine learning method, gradient boosting method (GBR) is applied to calculate the diameter from the tilt angle. The monitored data of tilt and diameter reveal 2 deformation modes, the rotation and the ovalization, of the segmental linings during construction. The rotation is the main mode when the lining inside the shield tail and the maximum of rotation length is about 12mm. When the lining pulled out of shield tail, the ovalization becomes the main mode with about 2mm convergence of horizontal diameter happening in 1day. As the shield advanced, the horizontal diameter increases about 3mm in 6 months. The relationship between construction parameters and the deformations are analyzed. The cutter torque when shield advance is related to the rotation deformation. The tail grouting when the lining pulled out is related to the diameter convergence.

Keywords: shield tunnel, construction, wireless sensor network, segment deformation, tilt angle, diameter convergence