Bearing behaviors of rock-socketed piles in layered dynamically compacted soil-rock mixtures: A case study

After layered dynamic compaction (DC) treatment in a mountainous area with deep backfill in Chongqing, China, a series of pile tests and analyses were conducted to evaluate the vertical bearing capacity of rock-socketed piles and to investigate their mechanical characteristic and load-bearing behavior. Static pile load tests (SPLT) were carried out on three types of rock-socketed piles with different diameters (800 mm, 1000 mm, and 1200 mm). Based on the test data of pile reinforcement stress, the pile axial force, frictional resistance, and load-sharing ratio were calculated and analyzed. The results indicate that load-settlement curves of static load tests for all piles change progressively, and the S-lgt curves are relatively straight lines without obvious downward bending. The pile axial force exhibits the characteristics of “large at the top and small at the bottom”, resulting in stress concentration at the pile top, especially prominent in longer piles (lengths of 33.2–37.1 m). Additionally, the overall frictional resistance increases with the increase of pile top load. In shorter piles (lengths of 16.5–22.6 m), the frictional resistance presents a C-type curve with depth, while in longer piles, it presents an S-type curve distribution. Comparatively, the test pile bears the upper load mainly by the side friction resistance, which is more prominent in the longer pile. With the increase of pile top load, the load-sharing ratio of side friction decreases and the load-sharing ratio of pile tip resistance increases. • Stress concentration at the pile top is prominent, especially in longer piles, exhibiting a "large at the top and small at the bottom" characteristic. • Longer piles (33.2–37.1 m) display an S-shaped frictional resistance, and shorter piles (16.5–22.6 m) exhibit a C-shaped distribution. • The Q-S curves for piles with different diameters change gradually without distinct inflection points, while the S-lgt curves exhibit a linear trend. • Rock-socketed piles primarily bear loads through frictional resistance, particularly in longer piles.