Model test study of soil grouting effect on shield tunnel longitudinal structural behavior

Abstract

Soil grouting has been widely applied in many shield tunnel settlement rehabilitation projects worldwide. However, the effectiveness of grouting on tunnel longitudinal performance largely relies on experience and field detection. In this study, a self-designed grouting model system was used to conduct a series of tests investigating soil and structural behaviors during grouting. Various grouting parameters, including burial depth, grouting volume and times, and grouting pressure, were analyzed to assess their impact on tunnel mechanical deformation. Results indicate that slurry diffusion in sand involves both compaction and fracture mechanisms, and the compaction of the surrounding soil diminishes along the expansion direction of the slurry vein. Reducing burial depth, increasing grouting volume and pressure, and employing continuous grouting all can enhance the effectiveness of settlement reduction. However, these reductions in settlement are often associated with adverse circumferential joint deformations, particularly joint dislocation. Multiple discontinuous grouting and shallow buried strata would introduce more disturbances, causing greater variation in joint deformation and more significant dissipation of additional stress after grouting. These findings provide valuable references for optimizing grouting practices in similar engineering applications.