Analyses of the Ground Surface Displacement under Reinforcement Construction in the Shield Tunnel End Using the Artificial Ground Freezing Method

Abstract

There are stringent requirements on the vertical movement of a ground surface when using artificial ground freezing method to reinforce a shield tunnel in a city. This paper focused on the tunnel of Nanjing Metro Line Two between Yixianqiao and Daxinggong. Based on the discrete element thermo-mechanical coupling theory, the horizontal freezing reinforcement project was numerically simulated. The numerical results of the soil temperature field and displacement field are approximately compatible with the field measurements. When the tunnel was frozen for 40 days, an effectively frozen soil wall was created and satisfied the construction requirements. During the freezing construction, both frost heave and thaw settlement obviously occurred. Above the tunnel, the vertical deformation of the ground surface was symmetrical about the center of the tunnel and decayed towards the ends. The maximum vertical displacement of ground surface frost heave was 8 mm, and the maximum vertical displacement of ground surface thaw settlement was 18 mm. Increasing the depth of the tunnel embedment can result in a decline in ground surface displacement. The study serves as a viable means of predicting ground surface displacements.

Settlement Analysis of Ground Surface and Adjacent Building Caused by Driving and Expansion Excavation of Shield Tunnel Using Artificial Freezing Method

“…Xiang took the tunnel from Yixian Bridge to Daxinggong section of Nanjing Metro Line 2 as the research object. Based on the discrete element thermal-force coupling theory, the numerical modeling of horizontal freezing reinforcement engineering was established, which provides a feasible method for predicting surface displacement [12]. Ren studied the temperature field of the freezing process of the new curtain by means of numerical simulation and found the mechanism of the active freezing and thawing process of the new curtain freezing method in construction [13].…”