ZHENG C, SHANG W C, SONG H X, et al． Study on the bearing behavior of rock-socketed piles under horizontal multidirectional cyclic loading［J］. Journal of Henan Polytechnic University( Natural Science)， doi: 10.16186/j.cnki.1673-9787.2026020003.

doi: 10.16186/j.cnki.1673-9787.2026020003

Received：2026-02-02

Revised：2026-03-30

Online：2026-04-28

Study on the bearing behavior of rock-socketed piles under horizontal multidirectional cyclic loading (Online)

ZHENG Can1, SHANG Wenchang2, SONG Hexing1, LIU Junwei2,3, LAI Huaiyuan1,

HU Yukun2,QI Guangyu2, ZHANG Yingyu2, DAI Xingke2,4

1.Guangdong Electric Power Design Institute Co., Ltd., China Energy Engineering Group， Guangzhou 510670, Guangdong, China; 2. School of Civil Engineering, Qingdao University of Technology, Qingdao 266000，Shandong，China; 3. Qingdao Key Laboratory of Intelligent Port Construction and Operation and Maintenance, Qingdao 266520，Shandong，China； 4. Shanghai Municipal Engineering Design Institute (Group) Co., Ltd, Shanghai 200092, China

Abstract: Objectives For near-shore and offshore structures, the pile foundations are subjected not only to upper vertical loads but also to horizontal cyclic loads such as wind, waves, and currents during their service life. In response to the unclear horizontal bearing mechanism of rock-socketed single piles under different load paths, a self-developed horizontal cyclic loading test apparatus was used to conduct on-site cyclic loading tests in four loading orientations: 0°, 45°, 90°, and 135°. The study investigated the horizontal bearing characteristics of rock-socketed single piles under variable-direction cyclic loading. Methods To address the lack of clarity regarding the horizontal bearing mechanism of rock-socketed monopiles under different load paths, field tests involving cyclic horizontal loading in four directions (0°, 45°, 90°, and 135°) were conducted using a self-developed horizontal cyclic loading test apparatus. The study investigated the horizontal bearing characteristics of rock-socketed monopiles under multidirectional cyclic loading. Results The test results indicate that the horizontal displacement of the pile decreases with increasing embedded depth (rock-socketed depth). Variable-direction horizontal cyclic loading subjects the surrounding rock mass to cyclic pressures from different directions, leading to plastic deformation in the rock around the pile. This plastic deformation gradually stabilizes with changes in the horizontal loading direction and the number of cyclic loading cycles. The increase in bending moment of the pile is mainly concentrated within the first 15 loading cycles. After 1 000 cycles, the bending moment no longer increases. The restraining effect of the weathered rock layer on the test pile is primarily observed within the rock-socketed depth range of 0-1.5 m. The peak rock resistance around the pile occurs at an embedded depth of 0.5 m and remains unchanged with the number of loading cycles. As the number of cycles increases, the rock resistance gradually stabilizes. The p-y curves for horizontal cyclic loading at 0°, 45°, and 90° are approximately linear, while the curve for 135° loading is nonlinear. After more than 15 loading cycles, the reaction force around the pile begins to decrease, and the stiffness of the pile-rock interface declines. The stiffness of the pile-rock interface exhibits significant path dependency under variable-direction loading. Under such loading conditions, the pile-rock interface undergoes repeated shear slip, and the damage zones generated in different directions accumulate and superimpose. The influence zone of the surrounding rock expands spirally outward, intensifying compression and fragmentation, leading to a significant reduction in the stiffness of the pile-rock interface. Conclusions Multidirectional cyclic horizontal loads cause the horizontal bearing mechanism of rock-socketed piles to exhibit distinct path-dependent characteristics, with the stress patterns continuously evolving as the loading path progresses. The shallow strongly weathered rock mass plays a dominant role in controlling the bearing performance. Multi-directional cyclic loading exacerbates the degradation of the equivalent stiffness of the pile-rock system and drives the p-y response toward a nonlinear state. In later stages, rock mass failure becomes the key factor limiting the horizontal bearing capacity of rock-socketed piles.

Key words: multidirectional horizontal cyclic load; rock-socketed pile; rock resistance; p-y curve