Experimental investigation on rheological properties and diffusion-related performance of clay shock slurry for excavation gap filling during shield tunnelling

The clay shock method is used to fill the excavation gap caused by shield taper and deviation during shield tunnelling. The rheological properties and diffusion-related performance of clay shock (CS) slurry have an important influence on its ability. In this study, the authors tested the rheological properties of CS slurry by using a rotational viscometer with a stepless regulation in speed. The influence of the parameters of preparation of CS slurry on its rheological properties was analyzed. The results showed that the Bingham plastic model is more suitable for characterizing the shear thinning behaviors of CS slurry. The apparent viscosity and yield stress of the CS slurry first increased and then decreased with increasing duration and speed of stirring. They increased with the duration of standing and decreased with increasing the water-powder ratio of component A. The numerical diffusion simulations and model tests with constant pressure were carried out to investigate the influence of the water-powder ratio of component A, the permeability of the stratum, and the net injection pressure on its diffusion-related performance. The process of diffusion of CS slurry mainly involved filling and permeability diffusion. The filling diffusion stage mainly occurred in the first 30 s of injection and can reach 70-80 % of the final injection mass. The effect degree of the aforementioned factors on the diffusion distance of CS slurry was in the following order: permeability coefficient of stratum > water-powder ratio of component A > net injection pressure. CS slurry diffused over a distance of less than 10 cm in sandy soil, where this was negatively correlated with the viscosity of the slurry and positively correlated with the coefficient of permeability and porosity of the stratum. The filling time of the excavation gap was positively correlated with the viscosity of the slurry, negatively correlated with the net injection pressure, and was not significantly correlated with the coefficient of permeability of the stratum. The diffusion termination time was negatively correlated with the viscosity of the slurry, and positively correlated with the coefficient of permeability of the stratum and the net injection pressure.