Study On Enlarged Bearing Base And Bearing Behaviors Of Pedestal Pile Compacted By Column-hammer In Clay

Pedestal pile compacted by column-hammer is composed of the reinforced concrete pile shaft and enlarged bearing base.The bearing capacity of this type of pile derives mainly from two aspects: one is the rammed dry concrete base and the other is the compacted end bearing stratum by fillers.The pile has the advantage of high load-bearing capacity,low settlement and good economic benefits,etc.Several aspects are studied in the paper,such as the forming mechanism of enlarged bearing base,behavior and influence factors of bearing capacity.Firstly,according to the similarity theory,the outdoor model test is carried out.By means of site excavation,I found out the shaping condition of the enlarged bearing base and figured out how column-hammer shapes,aggregate size and soil moisture the character of enlarged bearing base,and came up with the value range of the enlarged bearing base's diameter correction factor KD when the enlarged bearing base in the clay.By the static load test,the bearing capacity between pedestal pile compacted by column-hammer and equivalent-diameter tubular pile is analyzed,came up with the principle of choosing pile-end resistance value features correction factor ?p.Studied the compaction influence region and effect by the light dynamic penetration test and laboratory soil test.Finally,according to the Tianjin engineering project,the changing regularities of pedestal pile compacted by column-hammer settlement and the displacement around the pile are studied by using the finite element software ABAQUS,and the factor affecting the vertical bearing of pile are analyzed.Also simulate and analysis the influence of the different enlarged bearing base diameters,the different length of the pile and the module of soil under pile to the vertical bearing capacity.The results show that,the finite element method in this model is consistent with the test results;With the increase of belled diameter,the vertical bearing capacity improved,the rise scope of bearing capacity apparently slow down until the D/d is greater than 3.0;when the module of soil under pile increase,the vertical bearing capacity apparently improved.