To investigate the behavior of deep excavations in basaltic formations, finite element models were developed based on field cases with on‐site monitoring data, facilitating a comprehensive analysis of the deformation patterns, environmental impacts, and stability of the excavations throughout the excavation process. The ground surface behind the excavation crest exhibited a concave deformation pattern due to the effect of surcharge loading, whereas the first and second platforms displayed uplift deformation resulting from excavation‐induced unloading and strata rebound. The overall deformation of the excavations was small, attributable to the high stiffness and strength of the basaltic strata, exhibiting magnitudes on the millimeter scale, and the reinforcement anchor rods/cables are mainly for safety reserve. In the excavation section (reinforced with row piles and prestressed anchor cables) close to an existing basement, the maximum vertical and horizontal displacements were evaluated at only 1.09 and 0.56 mm, respectively; the basement is unlikely to undergo significant deformation or cracking, thereby obviating the requirement of additional protective measures. In the standard cross section (reinforced with anchor rods and shotcrete), the ground surface settlement initially increases and then decreases with distance from the excavation crest, and the settlement approaches zero when the distance reaches 1.0 H e ( H e is the excavation depth). The primary impact zone for ground surface settlement in the basement cross section extends approximately 1.0 H e behind the excavation crest, while the main influencing zone for horizontal ground surface displacement extends to approximately 3.0 H e . The safety factor of the excavation exceeds the design code‐specified threshold of 1.35, suggesting that the excavations maintains stability throughout the excavation process. These research outcomes can provide practical guidance for the design and construction of deep excavations in the basaltic strata.
Xie et al. (Thu,) studied this question.