Numerical Simulation Study on Frost Heave during the Freezing Phase of Shallow-Buried and Undercut Tunnel Using the Freeze-Sealing Pipe Roof Method

Abstract

This article begins with the engineering geological conditions and freezing design scheme of the Gongbei Tunnel’s underground excavation section, then applies the mathematical model theory of the horizontal freezing-tunnel-formation freezing temperature field and frost heave displacement field, and builds a coupled two-dimensional finite element calculation model. The development law of the frozen soil curtain and the variation law of frost heave displacement during the freezing phase were studied by comparing on-site observation data. According to the findings of this study, the construction of the artificial frozen curtain is mostly based on two types of freezing tubes that freeze the soil between jacked pipes and seal the water. At 90 days, the thickness of the frozen soil curtain ranges from 2.32 m to 2.58 m, guaranteeing that its strength fulfills water-sealing safety criteria. The distribution and variation of frost heave displacement are highly related to engineering geological circumstances, the freezing scheme, the frozen soil curtain development process, and the pipe curtain structure. The maximum vertical frost heave displacement value at any time is located at the centerline, which is 155.67 mm at 90 d. The numerical simulation findings are acceptable and can potentially be utilized for predicting frost heave in subsequent projects. More research is required to effectively represent complicated working conditions and to develop more exact large-scale numerical models for tunnel excavation, support structure building, and other situations.