Study on Bearing Characteristics of Pile Groups Crossing Karst Caves

This study explores the bearing performance of asymmetric cave-crossing pile groups under actual karst geological conditions, aiming to reveal the mechanical response and bearing evolution mechanism of pile groups under different cave spatial forms and defect pile quantities. A verified finite element numerical model was adopted to carry out systematic analysis. Taking karst caves with a height of 12 cm as the research object, three typical cave configurations, including upper-passing, lower-passing, and beaded caves, were set, and the influence of 1–4 cave-crossing piles on pile group bearing characteristics was emphatically analyzed. The main conclusions are summarized as follows: (1) Affected by cave spatial symmetry, partial piles present identical Q-S, P-S, axial force, and shaft friction curves. All pile foundations show prominent end-bearing features with steep Q-S curves under different cave configurations and pile defect quantities. (2) With the increase of cave-crossing pile numbers, the axial force of defective piles is lower than that of intact piles, the overall bearing capacity of the pile group decreases, while the axial force and maximum end resistance ratio of continuous cave-internal piles increase. (3) The pile group stiffness redistribution effect reduces the top load and axial force of cave-crossing piles, lowering the effective bearing proportion and overall stiffness of the pile group. Continuous cave-penetrating piles bear more loads due to superior geological confinement and higher stiffness, resulting in increased axial force, earlier limiting shaft friction, and larger end resistance ratio. (4) The number of cave-crossing piles significantly affects the pile–rock interface shaft friction, changing the magnitude, quantity and position of friction peaks. (5) Pile axial force attenuates in both overlying sand layer and underlying limestone layer with a faster decrease rate in limestone; shaft friction declines between peaks and vanishes inside karst caves.