Objective To improve the soil strength and permeability performance of the surrounding ground in metro tunnel cross passages, an in-situ intratunnel permeation grouting experiment is carried out in a cross passage.

Method Based on an investigation of the groutability of the soil layers in cross passage, the grout mix proportions, permeation grouting parameters, and grouting scheme are determined, and the effectiveness of the permeation grouting is evaluated.

Result & Conclusion  The ultrafine cement grout exhibited good groutability in the ground of the cross passage, and the average grouting volume per unit length of the grouting holes met the design requirements. After grouting reinforcement, the recovery rate of rock cores obtained from drilling is high, and the rock quality designation （RQD） is favorable. The unconfined uniaxial compressive strength （UCS） of the grouted solid ranges from 3.6 MPa to 24.7 MPa, which far exceeds the design requirement of 2.0 MPa. The permeability coefficient of the consolidated body basically meets the design requirements. The land subsidence and groundwater level variations induced during the grouting process are small and could be essentially neglected.