Experimental investigation of shield tunnel face stability under dynamic cutterhead in sandy soil

Abstract

Ensuring the stability of the tunnel face is crucial for the safety of shield tunnel construction. To assess tunnel face stability during cutterhead operation, we implemented an experimental system incorporating the cutterhead. This system was then utilized to investigate the failure modes of excavation faces in sandy soil layers and the variation in support pressure. Nine sets of physical model tests were conducted using a 1/2 cross-section tunnel model with varying cutterhead states, rotation speeds, and opening ratios to investigate face stability under both static and dynamic conditions. Experimental results indicate that the rotating cutterhead significantly promotes soil movement, leading to higher limit support pressure. Specifically, the limit support pressure is highest when the cutterhead rotates, lowest when stationary, and intermediate when the cutterhead is removed. Neglecting the active rotation of the cutterhead during shield machine advancement could lead to an overestimation of face stability. In addition, elevating the opening ratio and rotation speed of the cutterhead results in an increase in the limit support pressure. Therefore, employing a lower rotation speed and smaller opening ratio for the cutterhead could enhance tunnel face stability.