Study on the Bearing Behavior of Bored Piles in Karst Area of Guizhou Province, China

The underground rivers and karst fracture networks develop in the Guizhou area. The bedrock predominantly comprises muddy sandstone with pronounced karst geomorphology, significantly compromising the bearing capacity of bridge pile foundations. To elucidate the impact of karst development on drilled shaft performance, two test piles from a highway project in Liupanshui City were subjected to experimental analysis, investigating the correlation between karst features and pile foundation bearing behavior. The axial force distribution pattern, lateral frictional resistance ( f s ) transfer mechanism, and tip resistance characteristics were systematically analyzed by in situ self‐equilibrium static load tests. The test data indicate that during O‐cell loading, significant relative displacement develops between upper and lower pile segments. The peak axial force consistently localizes at the O‐cell interface cross‐section. The attenuation rate is relatively fast downwards along the pile body, and the rate of upward decay starts fast and then becomes relatively flat. The f s exhibits nonlinear decay with diminishing pile‐soil relative displacement gradient, attaining its minimum magnitude within the pile tip region. The comparative analysis reveals that although the reaction force–displacement curve at the pile end of the lower pile section has similar nonlinear characteristics to the static load test. There are significant differences in the stress field distribution characteristics of the soil around the pile. In the self‐balancing method test, the soil around the pile shows an asymmetric stress distribution pattern.