Effect of different pile sizes on vertical bearing capacity of GFRP composite piles

BIAN Hanliang; MA Yuhao; ZHANG Jianwei; YU Lu; FAN Yalong

doi:10.16186/j.cnki.1673-9787.2022120033

Abstract：Objectives To explore the influence of pile length on the vertical bearing capacity of glass fiber reinforced composite piles(GFRP composite piles).Methods A series of model tests were performed to in-vestigate the vertical bearing capacity of ordinary reinforced concrete piles(RC pile)and GFRP composite piles,respectively.Simultaneously,the effect of pile length was analyzed through finite element analyses for the vertical bearing capacity.Results In the model tests,the vertical bearing capacity of GFRP composite piles was found to be greater than that of RC piles.When the pile top load is 6 kN,the lateral friction resis-tance of GFRP composite piles accounts for 34.1%of the pile top load,while RC piles account for 24.7%.GFRP material significantly changes the roughness of the pile body,enhances the interface friction charac-teristics of the pile body,and generates smaller end resistance under higher vertical loads.In finite element software simulation,compared with RC piles,the friction coefficient between GFRP fabric and soil is greater than that between concrete and soil,which is conducive to the development of lateral friction resis-tance of GFRP composite piles.The proportion of end resistance of GFRP composite piles with the same pile length is significantly lower than that of RC piles.Compared with RC piles with pile lengths of 5,10,and 15 meters,the lateral friction values of GFRP composite piles account for 35.69%,42.44%,and 50.54%of the ultimate bearing capacity of the pile.The lateral friction values of GFRP composite piles account for 42.44%,63.09%,and 75.69%of the ultimate bearing capacity of the pile,respectively.This indicates that GFRP composite piles improve their vertical bearing capacity by increasing lateral friction,and the longer the pile length,the more significant the improvement in the bearing performance of GFRP composite piles.Conclusions The vertical bearing capacity of GFRP composite piles with the same pile length is signifi-cantly higher than that of RC piles.With increasing length,the side friction of the GFRP composite pile in-creased,which led to the corresponding results:a higher ultimate bearing capacity in the pile foundation,and larger interface friction of GFRP composite pile-soil.The conclusions could provide some suggestions for the design of the vertical bearing capacity of GFRP composite piles..