Numerical Modelling of a Secant Caisson Wall Shoring System in High-Stress Shallow Bedrock

Summary

Abstract

This study presents the design and analysis of a secant caisson wall shoring system for a 45 m diameter shaft located in eastern Canada, intersecting soil and shallow bedrock with high in-situ stress. The challenging geological setting imposed stringent construction constraints, requiring innovative strategies to ensure stability and safety. Advanced numerical modeling using PLAXIS 3D was employed to incorporate high-stress conditions into the initial design phase, enabling proactive risk mitigation. A key challenge was managing the significant stress differential between soil and bedrock, as the caissons extend beyond the soil layer and partially penetrate the rock mass. Stress release in the rock was carefully addressed to minimize long-term impacts on the permanent structure, balancing immediate construction requirements with future performance. The findings highlight the importance of integrating stress considerations early in the design of secant/caisson walls for deep shafts in high-stress environments. This approach contributes to risk management in rock engineering by providing practical insights into numerical modeling and design optimization under complex ground conditions.