Research on the Reuse of Discharged Soil from EBP Shield Tunnels in Synchronous Grouting Material

Great practical significance and engineering application value can be achieved when the large amount of discharged soil produced by EPB shield tunnels is recycled and comprehensively utilized. As one of the key processes of shield construction, synchronous grouting needs a large amount of bentonite, cement, fly ash, sand, and other materials. The research on the reuse of shield muck as synchronous grouting material is carried out based on Zhengzhou subway project. The physical properties and phase of the discharged soil from EPB shield tunnels are studied by using laboratory tests and XRD. The statistics show that the shield muck meets the performance requirements of bentonite and fine sand in synchronous grouting materials. The optimal grout ratio of the reused muck is obtained based on the optimization idea of multiobjective programming by MATLAB. Considering the combined effect of seepage field, stress field, and the timeliness of the grout, the influences of grouting pressure and the filling rate of synchronous grouting on surface settlement, plastic zone of strata, and segment deformation are analyzed by using finite difference method. The results prove that the surface settlement and segment deformation can be better controlled when the grouting pressure is at 0.18 MPa and the grouting rate is at 120%–150%.

An Operating Model for an EPB Shield TBM Simulator by the Correlation Analysis of Operational Actions and Mechanical Responses

This study reports on the development of an operating model for an EPB Shield TBM simulator by the correlation between operating parameters. First, four main operating parameters required for excavation are analyzed, then multiple regression analysis estimates their requirements depending on the ground conditions and the TBM’s specifications. Further multiple regression analysis then determines the interactions between six operational actions and ten mechanical responses. Operating procedures are established, and interlock and warning alarm systems are designed for use in the operating model. Lastly, several simulations were tested for the operating model of the TBM simulator under various conditions.

A Data-Driven Method for Predicting the Cutterhead Torque of EPB Shield Machine

The prediction of cutterhead torque of earth pressure balance (EPB) shield machine is mainly studied. First, the idea of shield tunneling stage division is proposed. The process of shield tunneling from start to stop (or pause) is divided into start-up and stationary driving stages. Using the change point detection method based on linear regression, the separation points between start-up stage and stationary driving stage are identified from the original construction data, and the datasets of the two stages are extracted, respectively. Then, for the start-up stage, the linear regression method is suggested for the cutterhead torque prediction, since there is a strong linear correlation between the key parameters such as the cutterhead torque and the thrust force. Meanwhile, for the stationary driving stage, considering the fact that the key parameters vary smoothly and show obvious inertia, the long short-term memory (LSTM) network method can be used to establish the relationship model between cutterhead torque and other key parameters, such as the thrust force. Through the test experiments of construction data in Zhengzhou, Luoyang, and Dalian shield projects, the results show that the proposed segmented modeling method possesses good adaptability and the cutterhead torque prediction model has high prediction accuracy.