A novel filter cake formation model for slurry shield excavation integrating slurry seepage-particles clogging and deposition-soil skeleton compression

Abstract

Current filter cake formation models for slurry shield tunneling fail to take into account the bentonite particle grain size distribution and particle clogging mechanisms, and neglect the effects of skeleton compression caused by soil stiffness variations. However, during the filter cake formation, the particles with different diameters can reduce the pore volume through deposition and clogging, thereby increasing the soil stiffness and reducing permeability. This study considered the effects of bentonite grain size distribution and established a novel filter cake formation model including the coupling behavior of slurry seepage, particle deposition and clogging, and soil skeleton compression with stiffness variations. The proposed model was validated through the experimental results in Yin et al. [48]. The influences of particle deposition and clogging, and soil stiffness variations on filter cake properties were also investigated. The results show that the particle sieving- and bridging-induced pore clogging play the key role in the reduction of soil porosity and permeability at excavation face before filter cake formation. The volumes of sieved and bridged particles are 61.5 % and 33.7 % of the soil porosity loss, respectively. Neglecting the particle clogging and particle size distribution causes an overestimation of filter cake formation time by 89 %, potentially triggering the excavation face instability. After the filter cake formation, the pore volumes reduced by particle sieving (2.1 %), bridging (1.4 %) and deposition (2.9 %) have slight changes, whereas there is a significant increase in pore compression volume (71.4 %). The proposed model offers a possibility for the construction parameters optimization of slurry shield tunneling.