DOI: 10.12688/f1000research.180061.1 ISSN: 2046-1402

Influence of Geometric Configuration on Load-Bearing Capacity of Under-Reamed Piles in Saturated and Partially Saturated Clay – Experimental Work

Ali F. Al-Baidhani, Abdul Aziz A Al-kifae
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Background Under-reamed piles are commonly used to improve the load-bearing performance of foundations in cohesive soils. However, the combined effect of pile geometry and soil saturation on compressive behavior requires further clarification. Methods A laboratory experimental program was conducted on four types of aluminum model piles (straight shaft, single, double, and triple under-reamed) installed in reconstituted clay under saturated (100%) and partially saturated (60%) conditions. Load–settlement tests were performed to evaluate the influence of bulb number and position. Bulb locations were defined as A(S), B(S), C(S), and D(S), corresponding to one-quarter, midpoint, three-quarters, and full pile length, respectively. The soil water characteristic curve (SWCC) was also determined using the filter paper method and compared with sensor-based measurements. Results Under-reamed piles showed significant improvement in load-bearing capacity compared to straight piles. In partially saturated soil, capacity increased by approximately 36%, 83%, and 162% for single, double, and triple bulbs, respectively, while in saturated soil the increases were 42%, 108%, and 149%. The position of bulbs significantly affected performance, with higher capacities observed when bulbs were located closer to the pile tip. For double bulbs, capacity increased by 74%, 83%, 53%, and 46% at positions A(S), B(S), C(S), and D(S), respectively, under partially saturated conditions, and by 108%, 83%, 62%, and 45% under saturated conditions. The SWCC obtained using the filter paper method showed higher values compared to sensor measurements. Conclusions The results demonstrate that both geometric configuration and soil saturation play critical roles in controlling pile performance. Increasing the number of bulbs and optimizing their position, particularly toward the pile tip, significantly enhances load capacity in cohesive soils.

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