The Absence Architecture: Asymmetric Hollow Conduits as Passive Shear Keyways in Layered Geological Media

Delamination and shear failure along bedding planes, joint interfaces, and lithological boundaries represent the dominant failure mode in layered geological media, accounting for the majority of large-scale slope instability, landslide events, and underground excavation collapses. Existing stabilisation methods — rock bolting, grouting, dowel systems, and drainage networks — address this failure mode by adding material across or along the shear plane: tensile reinforcement, filler mass, or fluid pressure relief. This paper proposes a fundamentally different approach in which the deliberate removal of material — the strategic introduction of empty, asymmetric, multi-axis hollow conduits penetrating across shear interfaces — functions as a passive macro-geometric keyway system that resists shear without any additive element. We term this framework the Absence Architecture. The core mechanism is the Negative-Space Keyway Effect: by creating irregularly shaped, non-uniform void geometries that cross the shear plane at varying angles, the remaining intact rock between conduits is forced into a complex three-dimensional interlocking topology. Any shear displacement requires the physical fracture of irregular macroscopic rock protrusions — the teeth of the keyway — rather than the sliding of smooth surfaces past each other. We demonstrate that this mechanism is physically distinct from existing applications of subsurface voids in geotechnical engineering, which treat voids exclusively as structural liabilities or passive drainage conduits. We formalise the spatial asymmetry principle — that non-uniform conduit orientation eliminates continuous failure planes — and apply it to both theoretical slope stabilisation and the retrospective structural analysis of ancient rock-cut architecture. The framework generates testable predictions amenable to Finite Element Analysis and Discrete Element Modelling, and proposes a new design parameter — the Keyway Disruption Index — for quantifying shear-resistance enhancement from void geometry.