Study On Working Mechanism And Bearing Behavior Of Reamed Precast Pile

As a new type of pile foundation,the grouting pile in the hole is first formed by drilling machine,then filled with precast cementing materials such as cement mortar or fine stone concrete,and finally pressed into the precast high strength concrete pile.Compared with the traditional cement-soil composite pile,the quality of cement mortar is easier to control and the compressive strength is higher,which overcomes the disadvantages of effective pile length,high soil layer requirement and easy crushing of the outer wrapping material.However,at present,the application practice of this pile type is insufficient,theoretical research is even more scarce,and the cognition of its bearing capacity,design theory and structural requirements is still incomplete.Therefore,it is of great engineering significance to study the working mechanism and bearing characteristics of piles after grouting in holes.Aiming at the interface characteristics and load transfer mechanism of pile after grouting in hole,the main work completed in this paper includes the following aspects:(1)Based on the laboratory interfacial shear test,the variation trends of shear stress and shear displacement of various surfaces(concrete-cement mortar and cement mortle-soil)of post-planted piles were analyzed.Combined with grout penetration test and pile sinking model test,the influence of post-implanted prefabricated piles on the pile sinking of grout in the hole and surrounding soil was discussed.(2)Based on the in-situ static load test,the bearing capacity of post-implanted piles with different diameter of expanding holes was studied.The bearing mechanism and vertical load transfer rule of post-implanted piles after grouting in holes were revealed through calculation and analysis of axial force of piles and friction resistance of various surfaces.(3)Based on the results of interfacial shear test in laboratory,the ABAQUS finite element analysis software was used to establish the vertical bearing model of pile after grouting in hole.The rationality of the model was verified according to the results of field static load test,and the influencing factors(strength of expanded material,bearing mode,etc.)of pile bearing characteristics were further analyzed.The estimation method of ultimate bearing capacity of pile after grouting in hole is discussed.