Grouting reinforcement and effect evaluation of the inlet section of a red-layer shaly sandstone tunnel

In this paper, a red layer soft rock tunnel project in Jiangxi is used to analyze the grouting reinforcement. The surrounding rock of the entrance section of the tunnel is characterized by high fragmentation, poor integrity and abundant groundwater. On the basis of consideration of engineering practice, a grouting reinforcement scheme with the small pipe pre grouting and full section radial grouting is determined. According to theory and empirical formula, the relevant grouting parameters are determined. Through the field monitoring, the grouting effect is evaluated in detail. The monitoring results show that the grouting forms a relatively stable grouting ring outside the lining, which reduces the water softening degree of the surrounding rock, improves the strength of the surrounding rock and reduces the coefficient of permeability of the surrounding rock. Finally, the vault settlement and surrounding rock convergence eventually tend to be stable. The surrounding rock of the right wall has a higher degree of fragmentation, and the grouting effect of the vault surrounding rock is poor. Therefore it is suggested that the support of the right wall and vault is strengthened.