Experimental research on influencing factors of uplift pile bearing capacity and deformation law of group piles
The in-depth research on the bearing failure process and influencing factors of uplift piles,as well as the collaborative working characteristics of pile groups,were conducted using a self-developed pile foundation indoor uplift testing device and numerical simulation technology.The results show that the bearing failure of uplift piles goes through four stages.In the initial stage of bearing,the lateral friction resistance at the top of the pile first takes effect,and the soil at the top of the pile undergoes plastic failure.As the uplift load increases,the pile body undergoes relative displacement,and the soil around the pile undergoes plastic failure due to the lateral friction resistance of the pile body.When the axial force of the pile body is transmitted from the top of the pile to the bottom of the pile,an uplift"adsorption force"is generated at the bottom of the pile body,accompanied by local plastic failure of the soil.As the plastic zone of the soil around the pile expands and connects,the bearing capacity of the uplift pile reaches its limit.The length-diameter ratio of the pile body,the friction coefficient of the pile-soil interface,and the soil pressure on the pile side are positively correlated with their bearing capacity.Among them,the length-diameter ratio of the pile body has an important impact on the"adsorption force"at the pile end.During the uplift process of pile groups,the lateral frictional resistance of corner piles is fully utilized,the displacement of the pile body is minimized,and the ultimate bearing capacity is maximized.The displacement of the central pile body is the highest,and the ultimate bearing capacity is the lowest.The distance-diameter ratio affects the pile group effect of uplift piles.When the distance-diameter ratio increases from 2 to 8,the lateral friction resistance of the pile body increases by 30%.Use a distance-diameter ratio of 8 as the recommended value for pile group engineering,and a range of 6-10 as the recommended distance-diameter ratio for pile group engineering.
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