Abstract：Based on the shield tunnel of Foguan Intercity Railway over-crossing Guangzhou Metro Line 7 in completely weathered granite formation, and considering the characteristics of completely weathered and dense granite formation, low permeability and over-crossing of two layers and four lines in complex stratum, the two challenges of reasonable value of grouting pressure and deformation control of existing tunnel encountered in practical projects were solved by means of field monitoring and three-dimensional dynamic finite element simulation. The optimal grouting pressure was determined by simulating the influences of different grouting pressures on the dynamic uplift deformation of existing tunnels and ground surface settlement. In addition, because the double-layer four-line overlapped crossing conditions had a greater impact on the disturbance of existing tunnels, the measures of controlling the deformation of existing tunnels were put forward in combination with engineering practice, in order to avoid the danger of segment dislocation and concrete cracking. The results show that when the grouting pressure of 0.5MPa is set in the completely weathered rock stratum, the ground surface settlement and deformation of existing tunnels can be reasonably controlled; for the influence of crossing construction on the vertical deformation of existing metro tunnels, there is a “lag effect”; after crossing of single-line shield tunnel, the vertical deformation of existing tunnels presents a normal distribution curve of single-peak wave shape; after the second crossing of shield tunnel, the curve shape changes from the normal distribution to the M-like double-peak wave shape, and the locations of the wave peaks have an offset of about 2m. The eventual deformation of the cross-section of the existing tunnel segment appears to be “vertical duck egg” shape, with the transverse ellipticity of 1.4‰ and the vertical ellipticity of 0.71‰. Based on the analysis results, reasonable weighting measures were taken in the project, and the uplift deformation of the existing tunnel was effectively restrained. The research results can be referred by those projects with construction of crossing tunnels in similar strata.
