Prediction of mud cake formation for shield tunneling based on cutterhead opening parameters

During the shield tunneling, mud cake is one of the most common causes of cutterhead failure. Mud cake formation is a typical nonlinear process. Although the mud cake may block partial or all of the cutterhead opening, the relationship between mud cake and opening parameters has not been investigated. In this study, a prediction model of mud cake formation based on cutterhead opening is developed. The shapes of central and peripheral opening are quantified by central angle, central length, average peripheral width and standard deviation. The geological type is considered as another input parameter. A dataset of 151 real shield machines is normalized. The state of mud cake is labeled to train a model based on support vector machine (SVM). The proposed model is validated against the dataset and three other engineering cases in varied cities. Mutual relationship between mud cake and opening parameters is also investigated. It is shown that opening parameters play important roles in mud cake formation. Increasing central opening angle is an effective method to avoid mud caking. The risk of mud cake is rather small for the central angle larger than 80°. For higher length of central opening, the central angle can be even smaller. By checking the opening parameters, the risk of mud cake can be reduced before actual excavation.