A computational method proposal on the determination of grouting parameters for shield construction in water-rich earth materials

Grouting process in shield construction plays an important role in controlling surface deformation and ensuring structural stability. The soil in water-rich areas has large water content and strong self-stability, and inappropriate grouting parameters will result in surface settlement and slurry dilution. The purpose of this paper is to propose a calculation method for grouting parameters in water-rich areas to ensure grouting effect and reduce deformation. Firstly, based on the maximum balance condition of soil, this paper derived a calculation equation for optimum grouting pressure considering the self-stability of soil by introducing the safety factor. Then, it analyzed the cause of the slurry loss, and the method for determining each expansion coefficient taking into account the time-varying nature was given. Finally, it put forward a method for modifying the mix ratio of grouting slurry in water-rich areas. In addition, it analyzed the relationship between grouting parameters and surface settlement through an engineering example. The study shows that the stability of the tunnel is related to the nature of the soil and the size and depth of the tunnel. The grout loss caused by the slurry infiltration is the most serious, and the slurry with modified mix ratio has excellent and stable performance. The grouting parameter determination method proposed in this paper improves the accuracy of parameter selection and has smaller surface settlement, which provides theoretical guidance for grouting construction in water-rich areas.