Abstract:An inevitable annular space named tail void is created at the rear of shield machines. This void is of importance with respect to subground settlements. During shield tunnel construction,the grout is being pumped in the void through a number of injection holes. With the hydration of cement and liquid loss after backfill process being completed,the grout volumes shrinkage leads to ground loss and induces the ground movement. The grout deformation and mechanical property variation can directly affect soil stresses releasing,ground movement,and earth pressures acting on segment. Utilizing the self-developed small scale element model of backfill grouting,the change laws of grout deformation are studied under different grouting pressures,different grout material mixtures in sandy soil. Based on grout deformation laws,mathematical model is proposed to simulate grout deformation. Identification of the gap parameter is one of the most important steps when using an analytical method to predict ground movement. Gap parameters can be obtained more exactly through grout deformation model.