Evaluation of seismic performance of prefabricated underground mid-partition walls connected by UHPC grouting sleeves

In underground structural systems, mid-partition walls exhibit significant seismic vulnerability in large-span prefabricated underground structures due to their relatively slender cross-sections and lower overall stiffness than primary structures. Leveraging the superior mechanical properties of Ultra-High Performance Concrete (UHPC), this study designed prefabricated underground mid-partition walls incorporating two connection types: UHPC grouted sleeve joints (Specimen A) and hybrid UHPC grouted sleeve-prestressed anchor joints (Specimen B). Large-scale quasi-static tests were conducted to evaluate the seismic performance of both configurations. The experimental results demonstrated that both joint configurations provided sufficient connection strength and enhanced the plastic deformation capacity of the mid-partition walls. All specimens exhibited biaxial compression-bending failure characteristics, with extensive concrete spalling at the base of the wall and yielding reinforcement deformation, ultimately forming plastic hinges in the localized area at the wall base. Compared with Specimen A, Specimen B exhibited a 19.3% increase in peak load, and a 24.8% increase in cumulative hysteretic energy dissipation. The reinforcement strain at the wall base was significantly higher than other areas, indicating that this region experienced the maximum bending moment and is a critical weak link in the seismic design of mid-partition walls. This research elucidates the enhancement mechanism of prestressed reinforcement for UHPC grouted sleeve connections. It quantifies seismic performance improvements, providing a robust foundation for implementing UHPC grouted sleeve technology in prefabricated underground structures.