Model test and numerical simulation of frost heave during twin-tunnel construction using artificial ground-freezing technique

Based on the actual twin-tunnel freezing project of the Shanghai Metro in China, this study aims to establish a model test system that can simulate horizontal ground freezing, and the temperature distribution and frost heave ‘displacement are investigated. The model test results show that the frost heaving displacement of the soil was closely related to the closure time of the frozen wall. When the sequential freezing mode was adopted in the model test, the frost heaving displacement during the freezing period of the downlink tunnel was smaller than that during the freezing period of the uplink tunnel under the influence of water migration. Considering two different freezing modes, namely, sequential freezing and simultaneous freezing of uplink and downlink tunnels, we conducted a numerical simulation of the horizontal ground freezing of the twin tunnels. Compared with simultaneous freezing, sequential freezing can reduce frost heave displacement to a larger extent. This study can provide a reference for the design and construction of twin tunnels using artificial ground-freezing technique.