Risk Analysis, Risk Assessment and Design of a New Developed Slope Stabilization-Paper

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The paper describes risk assessment and stabilization of a steep river-valley slope supporting a 160 m-high, 1.7 km-long motorway bridge. Inclinometer monitoring, applied through the observational method, identified downhill movement along a shear zone about 22 m below ground. The recorded displacement was approximately 2.5 cm between 2000 and 2016. Because slope failure could jeopardize the bridge piers, the required stabilization force was estimated at about 540 MN.<br /><br />The authors emphasize that geotechnical risk arises from the inherent uncertainty of soil conditions, while system risk occurs when a construction method is unsuitable for the ground and groundwater. Risk management should therefore combine thorough investigation, qualified specialists, independent peer review, and the observational method. Monitoring must be supported by design models, defined limits, and contingency measures; it cannot replace adequate ground investigation.<br /><br />A new stabilization system was developed to suit the steep terrain and avoid introducing large construction loads. It consists of six shafts, each 6.6 m in diameter and 45 m deep, arranged in two rows. Reinforced-concrete head beams connect the shafts and transfer loads to permanent anchors up to 55 m long. One shaft also serves as a drainage shaft, with horizontal drains, and permanent groundwater lowering contributes to stability.<br /><br />A nonlinear three-dimensional finite-element model was used to assess the system and its interaction with the slope. The analysis confirmed the estimated stabilization demand, showed that the anchored shafts could resist the forces associated with the worst-case failure scenario, and indicated that anchor loads would be distributed across each row. The authors conclude that the design can preserve the bridge piers’ support and satisfy Eurocode 7 requirements for overall slope stability.

Keywords

risk assessment

slope stabilization

river-valley slope

motorway bridge

inclinometer monitoring

observational method

shear zone

groundwater lowering

finite-element model

Eurocode 7