The Horizontal Bearing Capacity Of The Strength Composite Pile And Tis Practical Calculation Method

The strength composite pile is formed by driving precast pile in the large diameter cement-soil pile before its setting and hardening.This type of pile can not only give full play to the advantages of high bearing capacity of the precast pile,but also provide frictional resistance by using the solidification effect and large surface area of the large diameter cement-soil mixing pile.The complementarity of the two types of piles is strengthened,which has been widely concerned and applied by the engineering community.There have been a lot of research results on the vertical load behavior of the strength composite pile,but little research has been done on the horizontal load performance of strength composite piles.The effects of design parameters(such as pile length,pile diameter,pile strength,etc.)of cement-soil piles on the horizontal stress and deformation characteristics of the strength composite pile and the design and calculation methods of the strength composite pile under horizontal loading need to be studied.For this reason,aiming at the problem of horizontal bearing capacity of strength composite piles,field test,numerical simulation and theoretical analysis are combined to study the characteristics of horizontal bearing capacity of the strength composite pile,the main influencing factors of horizontal bearing capacity and the practical design and calculation methods.The main research contents and results are as follows:(1)The horizontal load test of the precast pile and the strength composite pile is carried out.The horizontal load bearing characteristics of the precast pile and the strength composite pile under different loads are analyzed,and the influence of cement-soil pile on the force and deformation characteristics is clarified.Under the action of horizontal load,the existence of cement-soil pile promotes the exertion of horizontal resistance of soil,reduces the bending moment of pile body,and improves the bearing capacity and deformation capacity of strength composite piles.(2)The numerical calculation model of the precast pile and the strength composite pile under horizontal load is established.The horizontal bearing characteristics of the strength composite pile under horizontal load and displacement control are compared and analyzed.Besides,the horizontal bearing mechanism of strength composite pile is clarified.The deformation and stress distribution of the strength composite pile and precast pile are similar,which indicates that the m method is suitable for determining the horizontal bearing capacity of strength composite piles.(3)The numerical calculation models of the horizontal loads of the strength composite piles with different parameters of cement-soil piles are established.Furthermore,the effects of the length,diameter and strength of the piles on the stress of the strength composite piles and the exertion of the resistance of the soil around the piles are discussed.When horizontal bearing capacity is controlled by horizontal displacement,compared with single precast pile,the increase of horizontal bearing capacity of the strength composite pile increases linearly with the length of cement-soil pile,pile diameter and pile strength.Increasing the length,diameter and strength of cement-soil pile in strength composite piles can obtain greater horizontal resistance of soil,which has less influence on the internal force of pile.Therefore,cement-soil piles can be regarded as soils with high strength and modulus.(4)Through the analysis of numerical calculation parameters,the influence law of the length,diameter and strength of cement-soil pile on the horizontal bearing capacity of strength composite pile is explored.For the project of controlling the horizontal bearing capacity,the design of the length of cement-soil pile in strength composite pile should be no less than 4.0m.The relationship between the thickness and strength of cement-soil pile increase linearly with the increase of horizontal bearing capacity,and the formula for calculating the horizontal bearing capacity of strength composite piles based on the parameters of cement-soil piles is established.(5)Considering the effect of cement-soil pile,the method of calculating the horizontal bearing capacity in the Technical Code for Building Pile Foundation(JGJ 94-2008)is amended,and the method of calculating the horizontal bearing capacity of single pile of strength composite piles based on the modified m method is obtained.