This research addresses the critical challenge of progressive collapse in Reinforced Concrete (RC) frames by establishing a rigorous multi-scale link between material fracture mechanics and macroscale structural hierarchy. The study investigates the highly non-linear 'Ductile-to-Brittle' transition, identifying two dimensionless ratios as the fundamental governing parameters: the Geometric Ratio (a/H), which marks the onset of brittle behavior at a threshold of approximately 0.5, and the Energetic Ratio (L
Abstract This research addresses the critical challenge of progressive collapse in Reinforced Concrete (RC) frames by establishing a rigorous multi-scale link between material fracture [...]
The accurate characterization of in-situ stress states within rock masses is a critical prerequisite for the safe design and construction of road and railway tunnels. This paper synthesizes and extends the reservoir geomechanics framework developed by Zoback (2010, Stanford University) — originally conceived for petroleum wellbore applications — and rigorously adapts it to the problem of underground rock excavation in civil engineering contexts. The paper presents a new analytical methodology, the Integrated Stress Analysis Framework for Rock Tunnels (ISAF-RT), which combines in-situ stress characterization techniques (extended leak-off tests, hydraulic fracturing in pilot boreholes, wellbore breakout analysis) with classical rock mechanics tools (Kirsch analytical solution, Mohr-Coulomb and Hoek-Brown failure criteria, ConvergenceConfinement Method) within a unified probabilistic design workflow. The ISAF-RT framework introduces a novel six-phase sequential procedure that explicitly accounts for tectonic stress regime (normal, strike-slip, thrust faulting), anisotropic stress ratios (K₀), rock mass quality (GSI index), and time-dependent deformation, enabling the engineer to select appropriate support systems with quantified reliability. Application of the framework is demonstrated through numerical examples representative of Alpine railway tunnels and highway tunnels in folded mountain belts, where thrust-faulting regimes impose horizontal stresses up to 1.8 times the vertical overburden. The results highlight the importance of pre-excavation stress measurement campaigns and show that neglecting stress anisotropy can lead to underdesign of support by factors of 2-3. The ISAF-RT framework provides a rigorous, systematic, and practically applicable tool for geotechnical engineers engaged in subsurface infrastructure in challenging rock conditions.
Abstract The accurate characterization of in-situ stress states within rock masses is a critical prerequisite for the safe design and construction of road and railway tunnels. This [...]
The excavation of road and railway tunnels through inclined fractured zones represents one of the most challenging scenarios in underground engineering. The stress state within the rock mass undergoes complex perturbations when the tunnel axis intersects fault zones, shear bands, or preexisting fracture sets at non-perpendicular angles. Drawing on the theoretical framework developed by Zoback (2010) for failure analysis of deviated wells — specifically the generalised borehole wall stress equations, drilling-induced tensile fracture (DITF) diagnostics, and shear velocity anisotropy measurements — this article extends these principles to the three-dimensional geomechanical problem of inclined tunnel excavation. A critical review of stress transformation theory, breakout analysis for inclined openings, and the role of fracture dip in governing tunnel stability is presented. On this basis, the article proposes a new geomechanical methodology: the Integrated Stress Analysis Framework for Fractured Zones (ISAF-FZ). The ISAF-FZ is a sixphase, adaptive workflow that integrates in-situ stress characterisation, fracture network analysis, inclined opening stability assessment, support design, and real-time monitoring. Application to two case studies — the Gotthard Base Tunnel and the A1 Apennine Motorway Tunnel — demonstrates the framework's predictive capacity for support pressure requirements and excavation sequencing in crossed fractured zones. The results show that fracture dip angle is a primary control on required support pressure, and that the ISAF-FZ framework reduces prediction uncertainty by up to 35% compared to conventional isotropic approaches.
Abstract The excavation of road and railway tunnels through inclined fractured zones represents one of the most challenging scenarios in underground engineering. The stress state within [...]
Fault zones represent the most challenging geological discontinuities encountered during road and railway tunnel construction. When tunnel excavation intersects active or reactivated faults, the in-situ stress state within the rock mass undergoes profound perturbations: the fault core and damage zone display sharply contrasting mechanical and hydraulic properties compared with intact host rock, preferential slip planes exist at critically stressed orientations, and elevated pore pressures may transiently destabilise the excavation face. Conventional tunnel design methods, which treat the rock mass as a homogeneous elastic medium, systematically underestimate the support requirements and the risk of sudden failure events — including face collapse, large-displacement squeezing, and rockburst — in these settings. This article presents a rigorous geomechanical analysis of fault zone behaviour during tunnel excavation, grounded in the critically-stressed fault theory of Zoback (2010) and in the extensive body of evidence from deep borehole studies, seismic reflection surveys, and fault zone hydraulics. The Mohr-circle framework for evaluating fault criticality, the Stress Criticality Index (SCI) quantifying the proximity of a fault to frictional reactivation, the fracture density powerlaw model governing damage zone architecture, and the permeability-stress coupling equations are all translated into tools applicable to the tunnel design workflow. On this basis, the article proposes a new predictive framework — the Fault Zone Stress-Excavation Interaction (FZSEI) framework — that integrates SCI computation, damage zone geometry characterisation, pore-pressure transient modelling, and adaptive support classification into a unified design methodology
Abstract Fault zones represent the most challenging geological discontinuities encountered during road and railway tunnel construction. When tunnel excavation intersects active or [...]
The Gorges du Verdon (Haute-Provence, SW French Alps) constitute a spectacular deep fluvial canyon incised into Upper Jurassic to Lower Cretaceous Tithonian limestones of the Castellane fold-and-thrust belt, a region characterised by active thin-skinned compression (~0.1 mm/yr uplift), a complex network of N–S and E–W fault systems, and topographic relief of 300–700 m. Recent cosmogenic ³⁶Cl exposure dating by Cardinal et al. (2024) has quantified river incision rates of 0.06–0.20 mm/yr for the Late Pleistocene (60–15 ka), with a marked acceleration to 0.90
Abstract The Gorges du Verdon (Haute-Provence, SW French Alps) constitute a spectacular deep fluvial canyon incised into Upper Jurassic to Lower Cretaceous Tithonian limestones of [...]
Dam Engineering & Hydroelectric Energy 
Predictive Modeling of Ductile-to-Brittle Transition in Hierarchical RC Frames: A Comparative Study of Deep Learning and Machine Learning Surrogate Models 
