Experimental study on the influence of synchronous shield grouting parameters on earth pressure and grout distribution in sandy soil stratum

TThe disturbance induced by synchronous grouting directly affects the stability and safety of adjacent tunnel structures. Through model tests on synchronous grouting, this study analyzes the earth pressure and grout distribution patterns around tunnels in sandy soil strata. The experimental results show that when the grouting filling coefficient is 1.6, the injection of grout with 40% water content leads to a continuous increase in earth pressure, which later decreases gradually due to the dissipation of excess pore pressure. In contrast, after injecting grout with 60% water content, the earth pressure decreases initially as pore pressure dissipates rapidly, followed by a subsequent recovery as stress redistributes. When the water content of the injected grout is 40%, reducing the filling coefficient to 1.4 results in a decrease in earth pressure due to stress release upon shield tail withdrawal, with a subsequent increase as stress redistribution occurs in the later stage. Under the same filling coefficient, grout with 40% water content exhibits poor fluidity, leading to uneven distribution, while grout with 60% water content demonstrates better fluidity and a more uniform distribution. The grouting filling coefficient and grout water content significantly influence the variation of earth pressure and grout distribution around the tunnel. It is recommended that these factors be fully considered during construction to select reasonable synchronous grouting parameters, thereby minimizing the impact on adjacent structures.