Research On The Value Of Foundation Coefficient Around Pile Foundation Based On Horizontal Force

Pile foundation is an important foundation type in transportation,construction,underground engineering and other fields.With the development of major infrastructure construction,pile foundations are facing a more severe engineering environment and more functional requirements.The pile foundation usually penetrates the layered soil in the form of pile groups.The natural foundation soil layers deposited in different geological years have great differences in engineering properties.When analyzing horizontally loaded piles,the differences in the properties of each soil layer should be fully considered."Code for Design of Foundation and Foundation of Highway Bridges and Culverts"（JTG 3363-2019）^[1]provides specific methods for calculating the internal force and deformation of pile groups in pile foundations,but the conversion depth of m-values for horizontally loaded pile groups in layered foundations According to the calculation formula of single pile under load,the consideration of the influence between pile and soil in pile group is not perfect.Therefore,it is necessary to study the conversion depth of pile m-value of horizontally loaded pile groups in layered soil.In this paper,through theoretical analysis and derivation,model test research and finite element analysis,a comparative study of piles in horizontally loaded pile groups in layered soil is carried out.The main contents are as follows:（1）Summarize and summarize the current research status of single pile and pile group pile foundations subjected to horizontal loads.According to the basic theory of pile foundation m-method calculation,using the finite element of the bar structure,the internal force displacement calculation model of the horizontally loaded pile group on the double-layer foundation is deduced.When m₁>25000k N/m⁴,it can be calculated according to the simplified calculation method of the specification.When m₁<25000 k N/m⁴,considering the influence of the underlying soil layer on the pile,it can be calculated according to actual stratification.Due to the increase of the pile spacing,when m₁>15000k N/m⁴,the internal force and deformation of the pile are mainly affected by the upper soil,which can be calculated according to the standard method,m₁<15000k N/m⁴,should be calculated according to the actual stratification.（2）Based on the similarity theory,select the non-contact measurement system as the test measurement method,design and complete the model test.The results show that the horizontal displacement of the soil in front of the pile is divided into two stages along the depth of the pile body.When the buried depth is 0～110mm,the rate of change of the horizontal displacement is greater.Below the buried depth of 110mm,the change trend appears to slow.As the load increases,the depth of buried depth at which the horizontal displacement changes.The measurement line far away from the front pile,the horizontal displacement changes tend to be gentle.The horizontal displacement of the soil in front of the pile increases,and the main influence range of the horizontal displacement is expanded from 60mm to 190mm.The horizontal displacement of the soil between the piles increases with the increase of the horizontal load.（3）Based on the model test,a numerical model of the two-pile foundation of layered soil was established.The influence of the thickness of the upper soft soil,the thickness of the soft soil interlayer,the pile spacing,and the pile diameter on the properties of the two piles was analyzed,and the following conclusions were drawn:As the layer thickness increases,the horizontal resistance of the underlying soil to the pile body decreases,which leads to an increase in the horizontal displacement of the pile body.At this time,the calculation should be carried out according to the actual stratification.In the case of a weak interlayer,the pile displacement should be corrected or calculated according to actual layers.When calculating the internal force and deformation of the pile group,the influence of the underlying soil layer on the pile body should be considered.