Analysis Of Bearing Capacity Of Small Spacing Friction Pile Group Under Vertical Load

With the rapid development of economy recently,China invests a lot of money to the second-tier and third-tier cities to improve the traffic conditions,especially to the northwest Yunnan highway construction.This is conducive to the development of tourism in the northwest Yunnan province,facilitating the development of the border area and building a moderately prosperous society.However,engineering practice may encounter same cases;for example,group of pile spacing is too small.The traditional theoretical analysis and laboratory tests lag behind the demand of the engineering practice obviously.It is necessary to study the character of the small distance between the bearing capacity of the pile foundation and the deformation characteristics,ensure the safety of the bridge engineering and give full play to the bearing capacity of pile group at the same time.The paper establishes a finite element three-dimensional numerical model basing on the analysis of indoor test and theoretical calculation both at home and abroad,analyzing of the small spacing of pile group foundation vertical bearing characteristics and settlement calculation of the bridge project in Yunnan.The main research works and achievements are as follows:(1)Based on the relevant literatures on the basis of domestic and foreign groups to introduce the computing methods of single pile bearing capacity,pile bearing capacity,pile sedimentation and effective pile length,compare several commonly used classical methods the advantages and disadvantages,applicability on the basis of the bearing capacity of single pile by highway bridge specifications,pile bearing capacity by single pile bearing capacity parameter method and limit equilibrium method,the settlement of pile groups were calculated using summation method.(2)I analyze the applicability of finite element software in geotechnical engineering briefly,concise modeling steps of the numerical simulation software of Abaqus and analyze the selection of material constitutive models: Using linear elastic model about pile,Using Mohr-coulomb model about soil,Interaction with frictional contact(Tangential behavior using penalty function,contact method is used to conduct the hard)and Binding contact.(3)By Abaqus finite element numerical simulation software,3-D model calculation is applied to the small distance between low group piles and pile caps.This paper mainly discusses the pile group foundation in different pile spacing,pile length and pile number to the influence of the performance of vertical bearing.Comparison and analysis of the pile effect coefficients obtained by numerical calculation and theoretical calculation under different pile spacing.The following conclusions are drawn through the load-settlement curve:when the vertical load is small,each group of piles has little difference under different engineering.When the vertical load increases under the controlled conditions,the settling volume of the pile spacing under the working condition of 2d and 6d subsidence changes from large too small.When the pile foundation is increased,the average bearing capacity of single pile will also be increased at the same time,the space between the pile group effect coefficients will become more and bigger.The vertical bearing capacity of the pile group is increased and the condition of settlement deformation is smaller basing on the length of Pile in the 50m-80 m.When pile length increases to a certain degree again after increasing pile length,variations in the bearing capacity and settlement of pile group is smaller.With the increase of number of pile group,load-settlement curve changes larger.When the pile group to a certain amount,the number of pile group amplitude decreases gradually.The numerical simulation method doesn't appear to be much different from the pile group effect coefficient of theoretical calculation under the condition of different pile spacing.Although there have some misunderstandings between the numerical simulation methods with the theoretical calculation,the error is controlled in a reasonable range.At this present,the feasibility of the numerical simulation is verified.(4)Using two different methods of the pile group effect coefficient and limit equilibrium methods calculate the vertical bearing capacity of the pile group and compare the results.The result of the finite element numerical verified the applicability of the pile group effect coefficient;Basing on the theory calculation and numerical calculation,the rationality of the pile design is obtained.