Study on the Influence of different factors on cutterhead shield jamming of gripper TBMs in weak rocks

Abstract

In the construction of deep-buried and long-mileage tunnels, the use of tunnel boring machines (TBMs) is the preferred excavation method. However, TBMs encounter a variety of problems in adverse geological conditions. When excavating in weak rocks with high in situ stress, the large deformation of the surrounding weak rocks causes TBM jamming, which is very time consuming and expensive to deal with. In practice, the most commonly used method is the advanced geological prediction technology, and support systems are strengthened on the basis of the convergence–confinement method, which is composed of the longitudinal deformation profile (LDP), ground reaction curve, and support characteristic curve. In this work, the LDPs of surrounding weak rocks were obtained using numerical models in FLAC3D. The influence of the elastic modulus (E) of rocks, buried depth of a tunnel (BDT), and tunnel diameter on the cutterhead shield jamming of a gripper TBM was analyzed. In the analysis, the total length of the cutterhead and cutterhead shield of the gripper TBM was 4 m, and the friction between the cutterhead shield and the surrounding rocks was not considered. Results showed that increasing the overcut was the most effective method to prevent TBM jamming. Moreover, E and BDT exerted an obvious effect on the design value of the overcut. Several suggestions to prevent the cutterhead shield jamming of gripper TBMs and countermeasures to resolve such jamming in weak rocks were subsequently derived. The conclusions of this work can facilitate the selection of appropriate overcuts when designing the cutterheads of TBMs and help to prevent and control the cutterhead shield jamming of gripper TBMs in weak rocks.