Model test and numerical simulation of vertical bearing capacity and deformation characteristics of rock-socketed uplift pile in sloped ground

As transmission line projects continue to expand into the western mountainous regions of China, the need for more transmission tower foundations on steep hillsides has increased. However, research on the uplift bearing deformation characteristics of pile foundations under high-intensity wind and snow scenarios on sloped ground is lacking, and current specifications are insufficient. Therefore, laboratory model tests were conducted on rock-socketed uplift piles on both flat and sloped ground to investigate load-displacement curves, ground deformation and crack propagation, failure mode, axial force of pile, side friction of pile, and relative displacement between the pile and rock. ABAQUS numerical simulation results were compared to the model test results to validate the reliability of the numerical model and investigate the influence of steepness (slope angle) on the bearing capacity and deformation characteristics of rock-socketed uplift piles. The results demonstrate that the load-displacement curves for flat and sloped ground have similar steep shapes, and sloped ground can have an adverse impact on the bearing capacity and deformation characteristics of rock-socketed uplift piles. The decrease in pile bearing capacity is positively correlated to the steepness of the slope, with a decrease of 0%-12.8% for slopes of 0 degrees-30 degrees and up to 25.9% for a slope of 45 degrees. Bedrock failure surfaces mainly occur in the downhill slope within a range of 3.2d(d is pile diameter), as well as within a fan-shaped range of 120, while the failure range on adverse slopes is about ld, which is different from symmetrical and composite failure on flat ground. When the load on the top of the pile reaches approximately 80% of its ultimate bearing capacity, visible cracks can be observed in flat or downhill areas of sloped ground. These research findings offer a scientific basis for improving the design and specifications of uplift resistance capacity in transmission tower foundations on sloped ground.