Abstract: Viscous soil has obvious characteristics such as plasticity, expansion and shrinkage, and it is easy to induce cracking damage of lining. Combined with the specific engineering case, the water content test, brazing test and drilling verification of the tunnel inverted arch inspection section were carried out, and the bearing strength, water content and distribution of the clay soil layer were obtained, and the characteristics of the lining crack characteristics were preliminarily summarized. According to the comprehensive analysis results of monitoring data and numerical simulation, the formation mechanism of cracks was analyzed and the characteristics of cracks were verified. The results show that the correlation between the weak layer at the bottom of the invert arch and the tunnel settlement and the inverted arch crack is very significant; the weak layer at the bottom of the invert is easy to cause uneven settlement of the tunnel; the lateral uneven settlement tends to cause the inverted layer to appear oblique and longitudinal cracks; longitudinal uneven settlement is likely to cause circumferential cracks in the second lining. According to the research results, the reinforcement scheme is proposed in detail, and the grouting type, mode and size, spacing and arrangement of the tempering tube are designed. Field results feedback shows that the reinforcement measures have a good reinforcement effect.