The shield tail brush forms a ring-shaped 2-4 grease cavity sealing system between the shield tail shield shell and the assembled segment ring, preventing groundwater, soil sand, mud and synchronous grouting slurry entering the tunnel, to ensure the safety of tunnel environment clean and tidy and shield tunneling, so accurate grasp of the shield tail brush mechanical properties is to ensure that the shield tail seal and shield tunneling security. Based on Midas GTS, the elastoplastic force calculation model of tail brush was established to simulate the change of binding force during the loading and unloading process of tail brush. The rationality of the calculation model was verified by comparing with the test results. Meanwhile, the binding force, stiffness coefficient, residual height and residual Angle of the clamping plate were obtained. The results show that: 1) The variation of bonding force obtained by numerical simulation is basically consistent with the experimental data, which verifies the rationality of the established numerical model and material parameter selection; 2) In the process of shield brush compression, the shield tail clearance decreases gradually, the bonding force increases almost linearly, and the residual height and residual angle of the compression plate decrease almost linearly, but the plastic deformation proportion increases gradually while the elastic deformation proportion decreases gradually, and finally tends to account for about 50% each. 3) The elastic performance of the tail brush is the key to the sealing performance evaluation of the tail brush. Its elastic performance can be evaluated according to the binding force, stiffness coefficient, residual height and residual angle of the compression plate; 4) According to the failure situation of the tail brush on site, three failure modes are concluded to be related to the failure of the escape of the tail grease to maintain the stability of the grease pressure in the grease chamber, and the escape of the grease is determined by the elastic properties of the tail brush. The elastic performance evaluation index of tail brush established in this paper can be used as reference for performance evaluation of tail brush.

Due to the high mud content in the mudstone strata, the mud cake is easy to occur in earth pressure balance shield excavation. Through the improved direct shear apparatus, the interface tangential adhesion strength test was carried out on the mudstone slag sample considering the influence of temperature, and the growth law of adhesion strength was discussed. The influence of cutterhead on soil extrusion and interface adhesion strength of excavation face under different shield tunneling parameters is analyzed. Combined with the shear strength of mudstone, the analysis model of the occurrence conditions of the cutterhead mud cake and the influence of shield tunneling parameters on the cutterhead mud cake are proposed. According to the analysis model, the critical penetration of mud cake during EPB shield tunneling is obtained. The results show that: The shear strength and adhesion strength of clay are used as indicators to establish a judgment model for the risk of mud cake formation on the cutterhead, which has certain rationality; The adhesion strength of clay increases linearly with the increase of penetration, the decrease of opening rate and the increase of buried depth; For Nanjing Metro Line 6, the critical penetration of shield tunneling should be controlled below 1.9 cm/r. The research results can provide construction guidance for the prevention of mud cake in EPB shield.