Evaluating the interaction between tunnel excavation and battered piles: effects of depth and position using 3D numerical analysis

As urban areas continue to expand and densify, the demand for innovative transportation solutions, such as underground transit systems, has intensified. A critical consideration in such projects is the proximity of tunneling activities to existing infrastructure, particularly battered piles, which are widely used for their superior strength and ability to withstand lateral loads. Despite their importance, the effects of tunnel excavation on adjacent battered piles remain poorly understood. The research focuses on three critical tunnel depths: near the pile shaft, close to the pile toe, and below the pile toe. Additionally, it examines the position of the tunnel in relation to the batter of the pile, considering tunneling on the batter side, opposite the batter, and across the batter. Using an advanced numerical model simulating clay behavior, the study reveals that settlement and load transfer mechanisms of battered piles are significantly affected by tunnel position and pile embedment length. Key findings show that maximum settlement occurs when tunneling is near the pile and on the battered side, while the largest pile deflection is observed when tunneling occurs close to the pile shaft. The research also identifies a 'dragload' effect due to negative skin friction and induced bending moments when tunneling near the pile shaft. These insights are crucial for optimizing the design and performance of battered piles in tunnel projects, ensuring their resilience and minimizing risks to surrounding structures. The study contributes to a better understanding of soil-structure interaction in urban tunneling, providing valuable guidance for engineers and researchers.