Uplift Resistance Capacity Of Anchor Piles Used In Marine Aquaculture

Anchor are an important part of the mooring system of marine aquaculture facilities,and their uplift resistance capability directly affects the safety of marine aquaculture.As a simple and low-cost anchor member,the anchor piles is widely used due to its advantages of accurate positioning and difficult to change the position of the anchor.Due to the special application scenarios,there are few research results on the uplift resistance capability of anchor piles.The pile structure is usually used to bear the pressure load.In the marine aquaculture,the anchor pile mainly bears the oblique tensile load.There are vertical and horizontal contact between the anchor pile and the soil,even if the fluid-solid coupling phenomenon is not considered,the interaction is also very complex.In addition,the main environmental loads in the marine environment are cyclic loads such as wind,waves,and flows.Fishermen rely on experience in the selection,installation and maintenance of piles and anchors in marine aquaculture,lack of theoretical basis,and it is difficult to guarantee the safety performance of aquaculture structures.Therefore,this paper studies the uplift resistance of anchor piles used in marine aquaculture.Through the establishment of indoor model experiments,the ultimate uplift resistance of anchor piles and the influence of cyclic loads on the uplift resistance capability of anchors piles under different working conditions are studied.The static pull-out performance experiment was carried out,and the ultimate pull-out performance of the pile anchor under different initial tension angles,pile diameters and buried depths was studied by using the rapid maintenance load method.The results show that increasing the initial tension angle of circular and square single piles can significantly improve the uplift resistance capacity.The failure load of the square single pile was slightly higher than that of the circular single pile.Increasing the pile diameter can effectively improve the failure load and delay the development speed of the pile top displacement.Increasing the embedded depth can effectively improve the failure load and increase the lateral displacement of the pile top.The uplift resistance capacity of the dual anchor piles was better than that of the single anchor piles.The layout configuration has little effect on the failure load,but has a large effect on the displacement development.In order to carry out the experimental study of cyclic loading,a set of cyclic loading experimental device was designed independently.The circular pile anchor with a pile diameter of 20 mm and a pile length of 500 mm was selected as the research object,and the influence of factors such as cyclic loading amplitude and cyclic loading angle on the pullout resistance was studied.The experimental results show that:（1）Under the vertical cyclic loading,the pile anchors with Q_C=0.6F_max and Q_C=0.8F_max are not pulled out and belong to a relatively stable state.Q_C=0.9F_max and Q_C=1.0F_max were destroyed after 285 and 85cycles,respectively,and belonged to an unstable state.（2）Under the inclined cyclic loading condition,with the increase of the initial tension angle,the cumulative vertical displacement of the pile anchor decreases,the lateral displacement increases,and the stiffness of the soil around the pile gradually decreases.According to the cumulative displacement trend and hysteresis curve,θ=30°andθ=45°belong to the stable state,andθ=60°belongs to the metastable state.（3）Under the inclined cyclic loading condition,with the increase of the loading amplitude,the cumulative displacement of the pile anchor increases,and the stiffness of the soil around the pile gradually decreases.From the cumulative displacement trend and command curve of a single group of experiments,Q_C=0.6F_max and Q_C=0.8F_max belong to a stable state,Q_C=1.0F_max belongs to the metastable state.In this paper,the pullout performance of pile anchors under different working conditions under static and cyclic loads is analyzed by carrying out model experiments.The inclined uplift mechanical properties of anchor piles in silt soil were preliminarily explored,which provided a theoretical basis for the design and use of anchor piles in marine facility aquaculture.