Abstract:

The reinforcement of karst cave is the key to shield tunnelling in karst areas. In this paper, the main geological risks when shield boring in karst strata with sandy soil cover are discussed; and then the ground surface reinforcement technology is introduced in terms of estimation standards of karst treatment, grouting program, grouting materials selection and grouting effect examination. Meanwhile, the grouting effect and the ground surface and building settlement are monitored. The study results show that: 1) The grouting reinforcement has reached good effect.2) The ground surface and building settlement induced by shield boring varies steadily.3) The ground surface grouting reinforcement is suitable for shield tunneling in karst strata with sandy soil cover.

Key words: shield tunnel, karst strata with sandy soil cover, grouting reinforcement, settlement monitoring