Performance and Mechanism of Double-Row Capsule Grouting to Protect Tunnels Adjacent to Excavation

Abstract

A new grouting technique, double-row capsule grouting (DRCG), has been developed and implemented in practice. This grouting technique could effectively mitigate excavation-induced tunnel movement and ensure the serviceability of metro lines. However, its control mechanism and the factors that influence its performance are not fully understood. Based on a case history that utilized capsule grouting the precision of the numerical model is validated. Parametric studies are conducted to investigate the influence of the grouting location and volume on the tunnel deformation, bending moment, restoration ratio, and shear strain of the soil. In addition, a comprehensive comparison between the conventional grouting technique and DRCG is performed to illustrate the control mechanism of this innovative technique. The results could contribute to a better understanding of the factors that impact the performance of DRCG and an optimal application of DRCG, which facilitates its efficient implementation and further development in engineering.