Abstract: In order to release the shield trapped in the consolidated water-rich sand stratum in a Shenzhen subway tunnel, the waterproof curtain by three-axis mixing piles was used to surround the shield in construction site, and the dewatering wells were laid out inside and outside the curtain for drainage. When the water level is down to the bottom of the shield machine, the chamber would be cleaned by hand. The theoretical dewatering arithmetic was used to calculate parameters such as the water inflow due to dewatering inside and outside the curtain and its influence radius, the number and spacing of dewatering wells, as well as the surface subsidence induced by drainage.Based on the relative reasonable initial design scheme of dewatering wells, a numerical simulation was carried out for further confirmation of the rationality and feasibility of the design scheme. The successful practice at site shows that it is very effective to dewater and release the trapped shield by the method combining theoretical arithmetic and numerical simulation, providing a reference to similar projects.