Performance Study of Casing Piles in Expansive Soil Foundations: Model Testing and Analysis

This study investigates the critical behavioral characteristics of pile foundations in expansive soil foundations through a series of model tests, including settlement, axial force, and side frictional resistance. The experiment initially utilized sand, bentonite, and gypsum as the fundamental materials for the preparation and composition research of expansive soil simulant materials. Subsequently, the performance of different types of model piles under various loads and water immersion conditions was analyzed. The results indicate that non-cased piles exhibit typical friction pile behavior, while PVC-cased and steel-cased piles effectively reduce side frictional resistance, resulting in a more uniform distribution of axial force along the pile. After immersion, the model test materials experience expansion, with a faster initial expansion rate and a more gradual later expansion rate. Different types of model piles exhibit different displacement characteristics, and the presence of an outer casing can reduce the uplift of the inner pile. Furthermore, PVC casing demonstrates better performance in handling negative frictional effects. This study provides valuable insights for the design and construction of pile foundations in expansive soil foundations.