Radial pre-grouting method before excavation of lower bench of confined water stratum tunnel

The invention provides a radial pre-grouting method before excavation of a lower bench of a confined water stratum tunnel. The radial pre-grouting method before excavation of the lower bench of the confined water stratum tunnel comprises the following steps that S1, after the excavation of the upper bench and initial support are completed, upper bench grouting holes are formed, a leakage point ofthe initial support is drained by using a grouting pipe, then upper bench radial grouting is carried out on the upper bench, the thickness of an upper bench consolidation ring is 3-5m, and the arrangement of the upper bench radial grouting holes and grouting process are determined according to the position of the leakage point, characteristics, water percolating capacity and water pressure; S2, lower bench radial pre-grouting is carried out on the surrounding rock, beyond 2m from a tunnel face, of the lower bench, the thickness of the lower bench consolidation ring is 7-10m; and the fissure water percolating direction