Model Tests On Cyclic Deformation Of Vertically Loaded Plate Anchors In Soft Clay Under Cyclic Loads

As an economical deep water mooring system characterized by large bearing capacity,easy installation and convenient recovery,Vertically Loaded Anchor is a promising form of foundation for large floating ocean structures.This form of foundation usually operates under working loads resulting from buoyancy of upper structures and cyclic loads generated by winds,waves and ocean currents.Thus,in the process of designing a vertically loaded anchor,it is of vital importance to evaluate its bearing capacity under both static and cyclic loads.Both load-controlled and displacement-controlled static loading tests were conducted on the vertically loaded anchor models embedded in saturated soft clay by using a self-developed electric servo loading apparatus.The embedment depth of vertically loaded anchors is 3 times and 5 times of the plate width and the acute angle between the plate and horizontal line is 30°.A normalized displacement failure criteria is set by normalization processing of loads and displacement according to bearing capacity and plate width.It can be observed that the failure displacement is 38% of the plate width with an embedment of 3 times the plate width,and 30% with 5 times.As a comparison,the bearing capacity is also calculated according to the empirical formula considering the effects of plate dimension,embedment depth and soil strength.The two methods reach an agreement in the results,and the rationality of the criteria can be certified.Model tests of vertically loaded anchors embedded in saturated soft clay are also conducted under combined static and cyclic loads,and the effects of static load ratio,cyclic load ratio on bearing capacity and deformation are analyzed.The embedment depth of vertically loaded anchors is 3 times and 5 times of the plate width and the acute angle between the plate and horizontal line is 30°.It is indicated that under combined static and cyclic loads,the deformation instability directly results from the accumulation of average displacement caused by the cyclic load;under static loads,the bearing capacity of anchors with different embedment depth changes in a similar pattern: both of them decrease linearly with the increase of cycle numbers;cycle numbers has an opposing effect on cyclic bearing capacity when the static load ratio is set: when the cyclic number increases from 100 to 1000,anchors with a static load ratio of 0.7 decreases from 98% to 90%,while anchors with the ratio of 0.5 decreases from 95% to 80%.When loaded with the same static load ratio,higher cyclic load ratio will lead to more cumulated pore pressure and cyclic pore pressure.Also,on this condition,shorter distance between soil in passive area and the anchor plate can account for more cumulated and cyclic pore pressure,and longer time for cumulated pore pressure to reach its static state.Numerical simulation is conducted to analyze the deformation process of vertically loaded anchor under static and cyclic loads by utilizing the incremental elasto-plastic FE method,which is able to simulate the deformation process of saturated soft clay by monitoring the cyclic load history.Compared with model test,it is found that accumulated displacement in the direction of horizontal line is close to the test results.