A Dual-Baseline Framework for Carbon-Geotechnical Event Governance in International Underground Construction Contracts

Underground construction creates a distinct carbon-governance problem because excavation, support, lining, logistics, programme and cost depend on ground conditions, while the related carbon budget may be administered through a separate record. Existing tunnel-carbon studies improve measurement, and standard-form initiatives address carbon management, but the reviewed literature does not provide an event-level procedure connecting carbon-budget adjustment to geotechnical risk administration. This article uses structured document analysis and a targeted integrative review of 39 legal, institutional, technical and methodological sources to develop a dual-baseline carbon-geotechnical governance framework for international underground construction contracts. The framework coordinates six interfaces: dependency mapping, common event identification, control attribution, coordinated assessment, decision authority and integrated verification. Four hypothetical pathways test internal coherence. A worked illustration applies frozen factors to five activity classes and produces a gross variance of 783,440 kg CO2e, assumed avoided emissions of 36,400 kg CO2e and a residual variance of 747,040 kg CO2e. Sensitivity bounds preserve the direction, but not the magnitude, of that illustrative result. These figures are scenario inputs rather than project findings. The framework separates technical verification from entitlement and liability, which remain dependent on the incorporated contract, mandatory rules, evidentiary treatment and governing law. Project-based and cross-jurisdictional testing is therefore required.