LAUSR

There are severe challenges for slurry pressure balance tunnel boring machine (TBM) tunnelling in sandy cobble soil of Beijing, Chengdu, and Lanzhou in China. And the problems caused by tunnelling from silty clay to sandy cobble stratum are more serious. With the change of stratum, the key parameters and surface settlement will change correspondingly. Controlling the key parameters and predicting the surface settlement accurately and efficiently is important for hazard mitigation and risk management. In this study, based on the Tsinghuayuan Tunnel project in Beijing, the key parameters and surface settlement while tunnelling from silty clay to sandy cobble stratum are studied. Firstly, the difference of key parameters while tunnelling in two different strata is analyzed. The analysis shows that immediate responses to changes in the stratum are recommended in order to ensure construction efficiency. Then, a refined 3D finite difference model is developed to simulate the slurry TBM tunnelling in different strata. For refined simulation, three key parameters obtained from measurement data were applied to the 3D models, and the simulation results were compared with the field data. Results show that the refined model has good performance in terms of the accuracy and efficiency. This study provides a good engineering practice reference for slurry TBM tunnelling in mixed strata.