Abstract: The composite soil-nailing wall support system is widely adopted in deep excavation engineering due to its strong economic advantages. However, in recent years, an increasing number of distress and failure incidents have been reported for excavations supported by composite soil-nailing walls. This paper examines a project in Shenzhen, detailing the overall excavation conditions, hydrogeological setting, support configuration, and the localized distress observed in a specific section of the composite soil-nailing wall. Based on numerical analysis, the study focuses on identifying the causes of the distress, evaluating the implemented reinforcement measures, and assessing their effectiveness, supplemented by comparative analysis with third-party monitoring data. The results indicate that for vertically excavated composite soil-nailing pits, water infiltration significantly reduces the shear strength of the slope’s geomaterials and markedly weakens the pullout resistance of soil nails, making localized instability highly likely. Introducing one to two rows of low-tension prestressed anchors can effectively control deformation and substantially reduce the risk of local failure. The engineering experience and analytical conclusions presented herein provide valuable reference for similar projects.

Key words: Composite Soil-nailing Wall, Deep Excavations, Hazards Analysis and Treatment, Deformation Control, Monitoring and Analysis