Evaluating the Seismic Performance of Combined Piled Raft Foundation (CPRF) Adjacent to Slope Crest

Landslide and seismic hazards pose substantial risks to structures situated proximate to slope crests, jeopardizing both structural integrity and occupant safety. Comprehensive understanding and assessment of these hazards are imperative for mitigating potential threats and ensuring the protection of buildings and their inhabitants. Pile foundations play a crucial role in providing stability and support to structures, particularly those in close proximity to slopes, against seismic events. This study endeavors to empirically and computationally investigate the influence of slope angle on the bending moment experienced by piles within a Combined Piled Raft Foundation (CPRF) system located atop sloping crests, utilizing shaking table experiments and numerical simulations employing the FLAC-3D finite-difference software. A total of 97 tests, comprising 47 experimental trials and 50 numerical simulations, were conducted. Experimental and numerical models of CPRF installed at various slope angles on sloping terrain, scaled at a 1/25th ratio, were subjected to harmonic sinusoidal seismic excitations. The outcomes highlight the criticality of accounting for topographic effects on both the magnitude and location of maximum bending moments of piles, a pivotal parameter in CPRF assessments on slope crests. Results demonstrate a notable elevation in pile bending moments on sloping terrain compared to flat ground, ranging from 2 to 6 times higher, with sloping ground exerting a more pronounced influence during intense seismic activities. This study underscores the importance of considering slope angle in the design and analysis of CPRF structures situated on slope crests, emphasizing the necessity for tailored strategies to address the distinctive challenges posed by these specific topographic conditions. Insights garnered from this investigation contribute to the formulation of robust measures for enhancing the resilience of buildings in high-risk regions susceptible to landslide and seismic hazards. The results show that for a 45° slope, the implementation of piles led to a reduction in AF of up to approximately 15% at the soil surface and around 25% at the foundation. Furthermore, the maximum bending moment at a slope crest of 30° was approximately five times greater, at 45° around eight times greater, at 60° about ten times greater, and at 90° roughly twelve times greater than those on flat ground.