Influence of Permeability of Filter Cake on Face Stability of Slurry Shield‐Driven Tunnels in Sandy Gravel Stratum

Abstract When the slurry shield tunneling in water rich sandy gravel stratum, it is easy to have problems such as difficult to form the filter cake and poor stability of the excavation face, and the filter cake is the key factor to maintain the stability of the slurry shield excavation face. Using finite element software, a three‐dimensional fluid solid coupling model of slurry shield tunneling is established. The influence of slurry parameters (slurry pressure and permeability coefficient of filter cake) on pore water pressure and excavation face stability during slurry shield tunneling is studied. The variation laws and internal relations of slurry parameters, pore water pressure and displacement are obtained. The results indicate that the slurry pressure and the permeability coefficient of the filter cake play an important role in maintaining the stability of the excavation face. Too large or too small slurry pressure will lead to forward or backward displacement of the excavation face, which is not conducive to the stability of the excavation face and causes large surface displacement. The excess pore water pressure will occur during tunneling, and the excess pore water pressure will decrease with the distance away from the center of the excavation face. When the slurry pressure is small, the excess pore water pressure is larger. With the shield away, the excess pore water pressure gradually recovers. When the permeability coefficient of the filter cake is large, it will accelerate the seepage of pore water in the excavation face, which will increase the excess pore water pressure value and lead to the increase of surface settlement.