Study of the Mechanical Influence of Ground Grouting on an Existing Shield Tunnel

In water-saturated karst environments, existing shield tunnels are under external water pressure, posing potential water inrush hazards. It is an effective method to improve the permeability of the strata near the tunnel by ground grouting. However, currently, there is limited research on the impact mechanism of ground grouting on existing shield tunnels, leading to blindness and increasing risks of construction. This study investigates the mechanical response mechanisms of ground grouting to existing shield tunnels by grouting simulation systems with numerical simulation validation. Based on field tests from the subway water inrush control project, the stress and strain characteristics of the shield tunnel segments under multifactor influences were analyzed. The results indicate that the following: (1) under the action of grouting pressure, the maximum stress on the tunnel segment is observed at the intrados of the springline near the grouting pipe. The segment contracts horizontally away from the grouting pipe and expands vertically upward. (2) The segment moves horizontally away from the grouting pipe, with no vertical displacement. (3) The greater the grouting pressure, the longer the grouting duration, and the more frequent the grouting, the more significant the impact on the stress of the segment. The research findings provide theoretical guidance for practical grouting engineering.