Model test and numerical simulation of foundation pit constructions using the combined artificial ground freezing method

With the increasing demand for water resources protection, realizing undrained excavations in foundation pit engineering has become a crucial technical problem to be urgently solved. In this study, we proposed a new design concept—the combined artificial ground freezing method. This method uses the diaphragm wall as the vertical support and the frozen curtain generated by freezing pipes in a temporary shaft as horizontal support. A model test and numerical simulation were performed to analyze the evolution law of the temperature field and the interaction mechanism between the freezing process and the diaphragm wall. The above research results show that the combined artificial ground freezing method could effectively and inexpensively seal the foundation pit. During the freezing period, the frost heave pressure on the contact surface of the frozen curtain and diaphragm wall was 30– 60 kPa and 25– 35 kPa in numerical simulation, much lower than the diaphragm wall's critical design value. Therefore, frost heave would not damage the diaphragm wall. In the end, the design criterion of the freezing pipes deflection form was proposed. The study provided a reference for designing and constructing foundation pits using the combined artificial ground freezing method.