doi: 10.16186/j.cnki.1673-9787.2022120033

Received: 2022/12/13

Revised: 2023/03/21

Published: 2024/03/25

Study on the effect of pile length on the vertical bearing capacity of GFRP composite piles

BIAN Hanliang1， MA Yuhao1， ZHANG Jianwei1， YU Lu1， FAN Yalong2

1. School of Civil and Architectural Engineering, Henan University, Kaifeng 475004, Henan, China; 2. The Fourth Construction Company Ltd of China Construction Seventh Engineering Bureau, Xi’an 710000, Shaanxi, China

Abstract:  Objectives This study aims to explore the influence of pile length on the vertical bearing capacity of glass fiber reinforced polymer composite piles (GFRP composite piles). Methods A series of model tests were conducted to investigate the vertical bearing capacity of ordinary reinforced concrete piles (RC piles) and GFRP composite piles, respectively. Simultaneously, finite element simulations were performed to analyze the effect of different pile lengths on vertical bearing characteristics. Results In the model tests, the vertical bearing capacity of GFRP composite piles was found to be greater than that of RC piles. Under a pile top load of 6 kN, the lateral friction resistance of GFRP composite piles accounted for 34.1% of the pile top load, compared to 24.7% for RC piles. The GFRP material significantly enhanced the roughness of the pile surface, improved the pile-soil interface friction, and reduced the end resistance under higher vertical loads. In finite element simulations, compared to RC piles, the friction coefficient between GFRP fabric and soil was higher than that between concrete and soil, which promoted lateral friction resistance in GFRP composite piles. The proportion of end resistance of GFRP composite piles with the same pile length was significantly lower than that of RC piles. For piles with lengths of 5, 10, and 15 meters, the lateral friction resistance  of RC piles accounted for 35.69%, 42.44%, and 50.54% of the ultimate bearing capacity. The lateral friction resistance of GFRP composite piles accounted for 42.44%, 63.09%, and 75.69% of the ultimate bearing capacity. This indicates that GFRP composite piles improve vertical bearing capacity by increasing lateral friction, and the longer the pile, the more significant the improvement in bearing performance. Conclusions In conclusion, the vertical bearing capacity of GFRP composite piles with the same pile length is significantly higher than that of RC piles. As the pile length increases, the lateral friction resistance of GFRP composite piles becomes more effective, resulting in higher ultimate bearing capacity. The interface friction of GFRP composite pile-soil is more favorable. The results of this study provide theoretical guidance for the vertical bearing capacity design of GFRP composite piles.

Key words: GFRP composite pile； vertical bearing capacity； model test； compaction degree； friction coefficient