According to the tail grouting of a double shield TBM tunnel in a soft stratum, the spherical hole model with small and large diffusion radius were established respectively considering the slurry diffusion and slurry displacement effect in the grouting compaction stage. An- alytical solutions of the spherical hole expansion stress and displacement field under the hole expansion-diffusion coupling effect are deduced. The interaction among plastic zone radius, reaming radius, initial radius of the spherical hole, and the seepage radius were analyzed. The results show that the larger the seepage pressure of grouting, the smaller the plastic radius. The larger the reaming radius is, the larger the plastic zone radius is. When the reaming radius reaches a certain value, the plastic radius tends to be stable, and the smaller the grouting seepage pressure, the earlier it tends to be stable. The above conclusions have important guiding significance for optimizing grouting parameters in weak strata.