ABSTRACT
The construction of underground transport structures in dense urban area is a potential source of major damages to existing buildings. The compensation grouting technique has proved his efficiency in several recent subway projects to reduce soil movements and associated risks. Compensation grouting operations appear to be a good means to optimize the safety of construction sites.
This paper presents a new approach in numerical modeling to simulate 3D ground deformations at several stages of the tunneling project;
at the design stage: prediction of tunnel induced ground movements and compensation grouting effect providing a map of the necessary injections for the whole tunnel alignment;
at the construction stage: daily tune-up for the assessment of grouting instruction on basis of the movements actually measured on the field.
A FLAC3D “Steady State” principle has been chosen in order to deal with possible long tunnel alignment and complex surrounding and to keep the computation time compatible with a daily tune-up of some model parameters at the construction stage. This new modeling principle is based on a grid mesh fixed with respect to the tunnel face. The tunnel progress is simulated by moving geology, surface loading and underground structures in the opposite direction. This technique gives the huge advantage that only a small size model is needed to cover the whole tunnel alignment.
This Steady State modeling principle is continuously linked with a complete data base in order to transfer in the model the needed parameters at each tunnel advancing stage (ground data, foundations data and compensation grouting data) and to store the results. In addition, this custom built database is designed to allow a day to day transfer between the construction site and the 3D model for grouting adjustments.
