Analysis of ground collapse caused by shield tunnelling and the evaluation of the reinforcement effect on a sand stratum

Based on laboratory and field tests for a cross-river highway shield tunnel in China, the causes of ground collapse by shield tunnelling in a water-rich fine sand stratum were analyzed. To ensure the safety of subsequent shield tunnelling, reinforcement treatment was carried out, and then the reinforcement effect was comprehensively evaluated. The results showed that the fine sand properties, slurry circulation quality, support pressure set and excess pore water pressure fluctuation are the main reasons for the collapse of sandy ground. The comparative analysis of the permeability coefficient of the stratum and tunnelling parameters of the shield indicated that the grouting reinforcement effect on the fine sand stratum was obvious and that the disturbance to the stratum can be effectively controlled.