Disturbance mechanical problems induced by synchronous grouting in deep shield tunnels

In order to study the disturbance influences of the surrounding soils and the existing double-arch tunnels induced by the synchronous grouting during the construction of deep shield tunnels, the effect of grouting on soils during the synchronous grouting is simplified as the problem of cylindrical cavity expansion in the infinite space. Considering the seepage effect of grouting on soils during the synchronous grouting, the construction disturbance mechanical model of synchronous grouting is established on the basis of the cylindrical cavity expansion theory and unified strength theory. The theoretical formulas for stress field, strain field and displacement field in the elastic-plastic zone under the influence of the synchronous grouting disturbance are deduced. The Hang to Hang zone shield tunnel of Xi’an subway No. 4 line is taken as an example. The results show that: (1) The influence of the grouting penetration pressure on the plastic zone is significantly greater than that of the grouting pressure on the plastic zone, which indicates the grouting disturbance zone can be reduced by controlling the grouting penetration pressure. (2) The significantly apparent disturbance influence of the existing tunnel under the action of the synchronous grouting when the adjacent double-arch tunnel is passed by newly-bulit shield tunnel, the grouting pressure and grouting capacity can be adjusted in real time, and the isolation and reinforcement measures are adopted to ensure the passing safety.