This study systematically investigated the influence of slope effects on soil-pile interaction in integral abutment jointless bridges (IAJBs) under cyclic loading through pseudo-static cyclic tests. While existing studies on the soil-structure interaction in IAJBs had predominantly centered on level-ground conditions, the asymmetric constraint effects of sloped terrains remained inadequately investigated. To address this research limitation, three reinforced concrete piles—with varying ratios (b/d = 2.0, 0.0, −2.0) of the distance (b) from pile side relative to slope crest to the pile diameter (d)—were embedded in layered clay-sand slopes and subjected to cyclic displacements. Key results indicated that decreasing the ratio (b/d) from 2.0 to -2.0 increased the maximum damage depth by 25% and expanded the crack distribution range by 50%. The lateral load and soil reaction of the pile in the slope-facing direction decreased by 29.1% and 28.9%, respectively, while backslope values remained stable. Both the equivalent viscous damping and stiffness in the slope-facing direction degraded by 12–32%. These findings clarified the asymmetric soil-pile interaction mechanisms induced by slope effects and provided critical references for optimizing pile embedment depth and seismic design of IAJBs in sloped terrains.

This study systematically investigated the influence of slope effects on soil-pile interaction in integral abutment jointless bridges (IAJBs) under cyclic loading through pseudo-static cyclic tests. While existing studies on the soil-structure interaction in IAJBs had predominantly centered on level-ground conditions, the asymmetric constraint effects of sloped terrains remained inadequately investigated. To address this research limitation, three reinforced concrete piles—with varying ratios (b/d = 2.0, 0.0, -2.0) of the distance (b) from pile side relative to slope crest to the pile diameter (d)—were embedded in layered clay-sand slopes and subjected to cyclic displacements. Key results indicated that decreasing the ratio (b/d) from 2.0 to -2.0 increased the maximum damage depth by 25% and expanded the crack distribution range by 50%. The lateral load and soil reaction of the pile in the slope-facing direction decreased by 29.1% and 28.9%, respectively, while backslope values remained stable. Both the equivalent viscous damping and stiffness in the slope-facing direction degraded by 12-32%. These findings clarified the asymmetric soil-pile interaction mechanisms induced by slope effects and provided critical references for optimizing pile embedment depth and seismic design of IAJBs in sloped terrains.

Integral abutment jointless bridges (IAJBs) offer superior structural robustness, seismic performance, and long-term durability owing to the elimination of expansion joints and bearings, making them particularly suitable for mountainous regions. However, when such bridges are constructed on sloping terrain, the abutment-pile system is subjected to asymmetric soil constraints—the so-called "slope effect"—which complicates the soil-abutment-pile interaction (SAPI). To quantify this effect, pseudo-static cyclic tests were conducted on an integral abutment-reinforced concrete (RC) pile system embedded in a layered clay-sand slope, taking the ratio of the distance from the pile side to the slope crest to the pile diameter (b/d) as the key parameter. Two configurations were tested: APSD-1 (b/d = 0.0, level ground) and APSD-2 (b/d = 2.0, 30°slope). The results show that the slope effect significantly weakens the lateral resistance and amplifies the asymmetric response of the system. Compared with the level-ground case, the peak lateral force in the slope-facing direction decreased by 33.1% and the overall system stiffness degraded by 24.8%, while the plastic hinge in the pile developed to a greater depth. The earth pressure behind the abutment exhibited similar distribution patterns in both configurations, but its magnitude in APSD-2 was approximately 4.6% lower at large displacements. The average soil reaction on the pile decreased to 0.932 times that of the level-ground case, with a pronounced asymmetry in the embedment depths of the maximum reaction between the backslope and slope-facing directions. In addition, the equivalent viscous damping ratio in the slope-facing direction was reduced by about 5% on average. These findings clarify the integrated interaction mechanism and asymmetric failure characteristics of the abutment-pile-soil system in sloping terrain and provide essential experimental evidence for the seismic design and performance assessment of IAJBs in mountainous regions.