Bearing Characteristics of Implanted Pile After Pre-bored Grouting in Pile-slab Subgrade
To investigate the bearing characteristics and load transfer mechanism of implanted pile after pre-bored grouting in pile-slab subgrade structure,relying on the pile project of pile-slab subgrade in Hefei-Zongyang section of G3W Dezhou-Shangrao expressway,two sets of field load test are conducted.Two groups of static load tests of precast implanted pile after pre-bored grouting under different reaming conditions are carried out.Considering the interaction among implanted pile inner core,outer cement mortar,and surrounding soil,the nonlinear mechanical behaviors of core pile-cement mortar interface and cement mortar-soil interface are revealed through a series of interface shear tests.A hyperbolic model and an elastic-failure model are adopted to characterize the shear behaviors of cement mortar-soil interface and core pile-cement mortar interface respectively.Based on this,a three-dimensional numerical analysis model is conducted for implanted pile after pre-bored grouting.The numerical model is verified by comparing the calculations with field test result,and further extended to reveal the load transfer behaviors of implanted pile after pre-bored grouting.The result indicates that the load at the end of implanted pile after pre-bored grouting is about 20%of the total load at the top of pile.the bearing characteristics of end-bearing friction pile is shown on the whole.The outer cement mortar with high-strength can effectively transfer core pile load to surrounding soil,and play a role in expanding core pile diameter.Under test conditions,the interface resistance between core pile and wrapped mortar is large at both ends and small in the middle along pile length,while the interfacial resistance between cement mortar and soil gradually increase with depth.Increasing the thickness of outer cement mortar is beneficial for improving the bearing performance of traditional precast concrete tubular pile.However,the thickness of outer cement mortar should not be too large,which is supposed to be 0.2-0.5 for effectively utilizing the synergistic effect of inner core precast pile bearing characteristics and core pile-cement mortar.
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