Numerical modeling and verification of grouting with mold bag treatment on seepage failure in foundation excavation

Abstract

This article presents a numerical modeling and verification on a new grouting technique, called mold bag prestress reinforcing method, which was successfully used for grouting control on seepage failure during a foundation pit excavation project. A numerical model is established based on finite element method to simulate the prestrss reinforcing and grouting process. The displacement and stress field during grouting process are calculated. Based on the calculation results, the rationale of the pretress method is clearly illustrated and the reinforcing mechanism is revealed. Results show that the horizontal displacements on the monitoring lines parallel to the mold bag are distributed in a parabola shape, and the prestress method effectively improves the mechanical properties of the soil. The influence of multimold bag interaction is also analyzed. The impermeability of the interior areas between two mold bags can be further improved due to a combining effect. The numerical results are compared with the actual excavation results of the foundation project. After grouting treatment, the water inflow amount reduced from 94 m3/h to 4 m3/h, which means more than 96% water inflow was successfully reduced. It is concluded that the numerical model can successfully simulate the process of prestress method and reveal the reinforcing mechanism.