Micromechanical investigation into the mechanism of slurry fracturing and the effect of covering depth concerning shield tunneling in a sandy stratum

With progressive advancements in slurry shield tunneling, increasingly larger tunnels are being constructed beneath shallow covering layers, leading to smaller cover-span ratios. If slurry pressure is not properly controlled, the covering layer is susceptible to fracturing or splitting. However, existing theories based on borehole expansion and filter cake forming fall short in interpreting the essence and mechanism of slurry fracturing in a discrete medium. To address this issue, this work employs a numerical approach grounded in laboratory experiments. This study offers a fresh perspective on the progression of slurry fracturing in sandy stratum, enabling direct observation of events within the stratum and analyses on dynamics and responses of the earth at various covering depths. Furthermore, particle scaling laws have been introduced to ensure the consistency in stress responses between real-world physical systems and simulations. The validity of this numerical approach in modeling such phenomena is demonstrated both theoretically and logically. New insights into the mechanism of slurry fracturing in a sandy stratum are provided.