In order to solve the problem that shallow and small clearance tunnels are easy to cause city road to collapse and chapped, taking the Jinan Yuhan Road Tunnel under typical geological conditions as the research object, the stability criterion of the middle soil wall is determined using a mechanical model of the tunnel middle wall. A grouting test under different loads of undisturbed soil in the tunnel is designed, and numerical simulation of the grouting of the middle wall of different tunnel depths and spacing is performed. The results show that the stability of the middle wall of the shallow and small clearance tunnel is related to depth, spacing, and the physical-mechanical properties of soil. The physical-mechanical properties of soil change little after grouting reinforcement with the same final grouting pressure as the burial depth increases. The stability criterion curve of the middle wall of Yuhan Road Tunnel is obtained by the measurement results of grouting test samples, and the numerical simulation results obtained by the experimental parameters have a high degree of agreement with the theoretical curve. Based on the stability criterion curve, sectional grouting was performed in Yuhan Road Tunnel, and the soil around the tunnel was successfully reinforced.