Excavation-induced stress release and ground improvement depth in normally consolidated rock, transitional rock, and soil media

Excavation-induced stress-release governs the mechanical response of geomaterials and may influence ground deformation and foundation performance beneath excavation bases. Although the concept of normal consolidation is commonly associated with soils, stress-states governed primarily by present overburden conditions may also occur in transitional rock and rock masses. This study presents a simplified analytical framework for evaluating excavation-induced stress redistribution and for defining preliminary ground-improvement depth envelopes in normally consolidated geomaterials. The proposed formulation is based on a one-dimensional reference stress framework governed by self-weight and reformulates the overconsolidation ratio (OCR) to represent excavation-induced stress-release as a normalized indicator of unloading. Within this framework, the depth at which the normalized OCR approaches unity is expressed as a function of excavation depth, defining an asymptotic analytical limit associated with the attenuation of excavation-induced stress redistribution. For normally consolidated soils, this limiting depth is approximately proportional to excavation depth (≈ 201·ED), which should be interpreted as a theoretical upper-bound envelope rather than a physically mobilized disturbance depth. The analytical framework is used to derive preliminary expressions for estimating ground-improvement depth in soils and to define ratio-based influence envelopes for transitional rock and rock environments. The proposed relationships are intended as screening-level engineering indicators that translate excavation depth and structural importance into rational ranges of ground-improvement depth. Although real excavation behaviour is governed by complex three-dimensional processes, recognition of such asymptotic stress-release envelopes may provide useful insight into the potential extent of excavation influence zone and support preliminary design assessment.