Abstract: To investigate the spatial variability of a sandlayer groutingreinforced body based on the water bleeding effect of cement slurry, experiments are conducted and the concept of attenuation rate of sandgrouting performance as well as the simplified equation of spatial distribution of attenuation rate is proposed. Accordingly, stability analysis is performed on a tunnel′s groutingreinforced body undercrossing sand layer by using a finite element simulation method. The crown settlement and water inflow of the tunnel are used as indices to evaluate the tunnel stability and validate the necessity of considering the spatial variability as well as the influence of the thickness of the reinforcement ring and the watercement ratio of the cement slurry on the tunnel stability. The results show that: (1) The watercement ratio has a significant influence on the spatial distribution of the groutingreinforced body performance. When the watercement ratio is ≥ 1.2, the performance of the groutingreinforced body is nonlinearly distributed spatially. In addition, the compressive strength and deformation modulus at the bottom are significantly higher than those at the top. Furthermore, the performance of the groutingreinforced body is negatively correlated with the height of the position. However, when the watercement ratio is ≤1.0, the impact of the water bleeding effect on the groutingreinforced body performance can be ignored. (2) When the watercement ratio is ≥1.2, the crown settlement and water inflow of the tunnel obtained by considering the spatial variability are both significantly larger than when ignoring the spatial variability and considering the spatial variability of the groutingreinforced body is of vital importance. (3) Finally, the crown settlement and water inflow of the tunnel present nonlinear characteristics with the change of the thickness of the groutingreinforced body ring. These two indices decrease with the increasing thickness, and the decreasing rate significantly declines when the thickness of the groutingreinforced body ring is extremely large; this is unfavorable to economic consideration. (4) The increase in the watercement ratio is unfavorable to the control of the crown settlement and water inflow of the tunnel. In addition, a lower watercement ratio should be chosen in the sand grouting engineering under the premise of infiltration.

Key words: tunnel engineering, sand layer, groutingreinforced body, watercement ratio, penetration grouting, cement slurry, spatial variability