Failure Mechanism of a Frozen Curtain Containing Grouted Soil and Its Design Method

In recent years, more and more underground projects have adopted a reinforcement technique combining grouting and the artificial ground freezing method. However, the failure mechanism of the new freezing–grouting support system in such conditions remains unclear. To address this gap, this study investigates shear and tensile strength parameters at the grout–frozen soil interface and analyzes the failure process of a frozen curtain containing grouted soil using the finite-discrete element method (FDEM). The results reveal that (1) the stiffness mismatch between the frozen grouted soil and the surrounding frozen soil significantly reduces the deformation resistance of the freezing support system. (2) Under external pressure, failure initiates at the grout–frozen soil interface, subsequently propagating into the surrounding strata and ultimately causing systemic failure. (3) Due to the influence of the temperature gradient during low-temperature loading, the orientation of interfacial ice crystals along the C -axis varies, resulting in discrepancies between laboratory and in situ residual shear strength. A new method is proposed to estimate the true residual interfacial strength. (4) Based on the FDEM simulation of the frozen grouted soil system, an optimized design scheme and a new methodology for determining frozen curtain thickness are developed.