Experimental Study On The Horizontal Bearing Characteristics Of Precast Concrete Enlarged Pile

Different from the traditional rigid composite pile,the expanded pile changes the cement-soil wrapper of the precast concrete pipe pile or section steel into cement mortar mixture,low-grade concrete,precast mixed cement-soil and other consolidations.Such outer wrapping materials are relatively uniform and have relatively high material strength.There have been a lot of studies on the horizontal load-bearing characteristics of traditional rigid composite piles or cement-soil composite pipe piles,but few studies have been done on the horizontal load performance of expanded piles,especially cement mortar expanded piles.The effect of expansion materials on the horizontal bearing capacity and deformation characteristics of precast pipe piles,and the design and calculation methods of expansion piles under horizontal loads need to be further studied.Aiming at the horizontal load-bearing problem of enlarged piles,this paper studies the horizontal load-bearing characteristics and design calculation methods of cement-soil enlarged piles and cement mortar enlarged piles through full-scale tests,numerical simulations,and theoretical analysis.The factors affecting the horizontal bearing characteristics of piles are discussed.The main research content and research results of the paper are as follows:(1)Full-scale horizontal load tests of cement-soil expanded piles and cement mortar expanded piles were carried out,and the horizontal load-bearing characteristics of cement-soil expanded piles and cement mortar expanded piles under different horizontal loads were analyzed.Under the same conditions,the horizontal critical load of the cement mortar expanded pile is larger than that of the cement-soil expanded pile,and the difference in the horizontal ultimate load value is smaller.The safety reserve between the critical load and the ultimate load of the cement-soil expansion pile is higher,which is greater than the safety reserve between the critical load and the ultimate load of the cement mortar expansion pile(2)Through the analysis of the fiber optic data of the enlarged pile body,it is found that the maximum bending moment of the cement mortar enlarged pile and the cement-soil enlarged pile appear at 5 times the pipe pile diameter below the ground.Under the same horizontal load,the cement maximum bending moment of the mortar expansion pile is obviously smaller than that of the cement-soil expansion pile.(3)A numerical calculation model for the horizontal load of the cement-soil expansion pile and the cement mortar expansion pile was established,and the horizontal load-bearing characteristics of the pile body were compared with the elastic model and the plastic model.It was found that the pipe pile adopts the concrete plastic damage model.The full-scale test data is more consistent.(4)The horizontal bearing characteristics of a single pipe pile were analyzed through numerical simulation.Under the action of horizontal load,the bending moment of the single pipe pile was obviously larger than that of the cement-soil expansion pile and the cement mortar expansion pile,and the horizontal ultimate bearing capacity was much lower than the expansion body.pile.The prefabricated pipe piles were cement mortar enlarged piles of PHC and PC pipe piles,and there is little difference in pile top displacement,pile body deformation,and pile body bending moment.The horizontal bearing capacity can be significantly improved by increasing the outer pile diameter of the cement mortar enlarged pile(5)The stiffness of the cement-soil and cement mortar coating materials was included in the calculation,and the calculation formula in the "Technical Specification for Cement-soil Composite Pipe Pile Foundation"(JGJ/T330-2014)was used to obtain a suitable cement-soil expansion pile and cement mortar expansion method of horizontal bearing capacity of body piles.