Analysis of a T-shaped gallery intersection drilled in anisotropic claystone

The Callovo-Oxfordian claystone (COx) is an anisotropic rock formation that serves as the host for the envisaged deep geological repository for intermediate-level and high-level long-lived radioactive wastes in France. In this context, the construction of several T-shaped gallery intersections is a common technique used for accessing the surrounding cells. In this work, a numerical analysis of a T-shaped gallery intersection excavation at great depth in the COx claystone is presented. A Drucker-Prager elastoplastic constitutive law with shear strength hardening is used to describe the rock matrix and the inherent anisotropy is implemented using the fabric tensor approach. Simulations include galleries with circular cross sections intersecting at a normal angle. The focus lies on the mechanical characterization of the zone around the intersection. The results highlight the plastic strain distribution around the main gallery walls. Furthermore, the extension of the plastic zone is presented.