Numerical Simulation Analysis Of Vertical Bearing Characteristics Of A New Type Of Root Pile

With the increase of super high-rise buildings in cities,new requirements have been put forward on the bearing capacity of pile foundations in engineering.Because the bearing capacity of ordinary equal-section piles is too low,This paper presents a new type of root pile,which has the advantages of higher bearing capacity and smaller settlement displacement than ordinary equal-section pile.In order to study the ultimate bearing capacity,vertical displacement,pile side friction and load transfer law of root pile,This paper uses FLAC3D to carry out numerical simulation analysis.(1)The new type of root pile is driven by hydraulic jack to press the block,which extrudes the cavity from the bottom to the top in the radial direction of the pile hole wall,cleans the hole,lowers the reinforcement cage and pours concrete,which forms a multi-layer root layer.The main difference between the pile and the existing common pile is that the radial root layer is evenly distributed outside the pile body.The cavity forming device is suitable for drilling holes with a diameter of more than 0.6m,and the depth of the root is not more than 0.5 times of the drilling diameter.(2)In order to study the bearing capacity of the root pile under the vertical load,by analyzing the load transfer characteristics of the pile-soil system,and assuming that the root pile is a linear elastic body,the bearing capacity estimation formula is obtained.(3)In order to analyze the ultimate bearing capacity of the root pile,the FLAC3D numerical analysis software is used to compare the root pile with the traditional equal section pile,and 28 groups of comparison models are designed to simulate and analyze the main factors affecting the vertical ultimate bearing capacity of the root pile:the spacing t of the root layer,the number n of the root layer,the depth d of the root layer and the thickness h of the root layer,respectively.Through the comparison of the bearing capacity of each model pile as well as the change of vertical displacement,the results show that the net spacing t of the optimal root layer is 1.0D(D is the pile diameter),the number n of the optimal root layer is 6,the depth d of the optimal root is 0.5D,and the thickness s of the optimal root layer is 0.375D.(4)Under the conditions of optimal root-layer spacing t,root-layer number n,root depth d,and root-layer thickness h,Comparison and analysis of root-type piles and equal-section piles.under the same condition,the ultimate bearing capacity of the root pile is increased by 166%compared with that of the equal section pile;when the root pile reaches the ultimate bearing capacity,the displacement is only 2.87mm,while the displacement of the equal section pile has reached 53mm.(5)Based on the analysis of the load displacement curve,the axial force of the pile shaft and the friction resistance of the pile side under the optimal conditions,it is found that the load-displacement curve of the pile of constant section develops rapidly and has abrupt changes At the point,the load-displacement curve of the root pile changes in a "decline slowly" type;and the axial force of the constant cross-section pile changes linearly The axial force of the pile body of the type pile is a sudden change of"Mutant" at the root layer;there is a limit value of the side friction of the pile with the same cross-section,after the pile body reaches the ultimate bearing capacity,the side friction of the pile no longer increases,and the change of the side friction of the root pile is basically the same as that of the pile with the same Gross-section,the difference is that after the side friction of the pile reaches the limit value,the end resistance of the root layer can continue to play a role,which is also the case The reason why the bearing capacity of root pile is better than that of equal section pile.Figure[53]table[10]reference[60]...