Study Of Horizontal Load Working Characteristics Of Finned Piles

Finned piles is a new optimized form of monopile foundation,in which rectangular steel plates are welded around the top of the pile to increase the area of the pile resisting horizontal load by changing the pile cross-section,so as to effectively improve the lateral resistance of the upper soil,reduce the horizontal displacement of the pile foundation and improve the horizontal bearing capacity of the pile foundation.Compared with increasing the pile diameter to improve the horizontal bearing capacity of pile foundation,the use of finned piles can save materials and reduce the economic cost,and also facilitate the site construction,which has very important application value in practical engineering.Therefore,it is important to study the working properties of finned piles under horizontal load for engineering guidance.In this thesis,the working characteristics of finned piles under horizontal load in sand foundation are studied by means of model test and numerical simulation.The influence of the fin width,fin length,pile diameter and soil strength parameters on the horizontal bearing characteristics of finned piles is discussed.The main work and conclusions of this thesis are as follows:(1)The horizontal loading model test of circular pile and finned piles with different fin sizes were carried out to analyze the effects of the fin width and length on the load displacement curve and internal force deformation of the pile.The test results show that the horizontal displacement and pile bending moment values of the finned pile under the same load are smaller than those of the round pile without fins,and the larger the load is,the larger the difference between the round pile and the finned pile is.The increase of the width and length of the fin can significantly reduce the displacement of the pile in the soil,after the width and length reach a certain value,the effect of increasing the width and length to reduce the displacement of the pile in the soil becomes weaker and weaker.The effect of increasing the width of the fin on the reduction of pile moment is better than that of increasing the length of the fin on the reduction of pile moment.(2)ABAQUS finite element software was used to establish a three-dimensional finned pile level model,and it was compared with the test data of the model test to verify that the numerical model can reflect the actual situation of the test more reasonably and reliably.Parameter sensitivity analysis of the horizontal bearing characteristics of the real size finned pile was carried out using the finite element software,and the effects of the fin width,length,pile diameter,friction angle and shear expansion angle within the soil were further studied.The results of numerical analysis show that the increase of width and length of fin can effectively resist the horizontal deformation of pile foundation,and it is suggested that the width of fin is 0.5 times of pile diameter and the length of fin is 2-3 times of pile diameter in practical engineering.When the fin size is the same,the finned pile can significantly reduce the pile displacement value with the increase of pile diameter,but cannot effectively reduce the pile bending moment value,compared with increasing the pile diameter,increasing the fin has a better effect on reducing the pile top displacement and pile bending moment.With the increase of the internal friction angle,the pile top displacement and the maximum pile bending moment values of the finned pile will be reduced,and the shear expansion angle also shows the same regularity.(3)In shallow soil,the incrase in fin length has no significant effect on the finned pile p-y curve,and the increase in fin width has a more significant effect on the funned pile p-y curve form.In the calculation of the p-y curve of large.diameter finned pile,the effect of the fin width effect should be considered,and the fin width(W)can be equated to the corresponding pile diameter size brought into the calculation of the foundation reaction modulus kini value.In the calculation of the ultimate soil resistance pu value of the finned pile,considering the effect of the finned pile shape,it is necessary to multiply the shape factor parameter ξ before the fin width,and calculate the pu value by D+ξ·2W(D round pile diameter)as the calculated diameter.The p-y curve obtained after considering the shape factor parameter ξ correction is in good agreement with the results extracted by ABAQUS.