Influence of multiple karst caves at the pile end on the bearing capacity of pile foundations based on ABAQUS
As an important load-bearing structure of buildings,the stability of pile foundations will directly impact building safety.With the expansion of engineering construction,foundations are frequently laid in an encounter with multiple karst caves.However,research on the influence of complex geological conditions with multiple karst caves at the pile end on the ultimate bearing capacity of pile foundations lags behind engineering practice.Therefore,studying this impact is crucial for engineering practice.In this study,a model of pile end containing multiple karst caves was established by the large finite element analysis software ABAQUS,with reference to a specific karst pile foundation project in the Hongshan district,Wuhan City,Hubei Province.This study aimed to explore the influence of cave shape,geometric characteristics,and spacing between karst caves on the ultimate bearing capacity of pile foundations under complex geological conditions with multiple karst caves at the pile end.This study involved the following steps.1.Geological models of piles and karst caves were established.This involved firstly determining the premise assumptions for finite element analysis,selecting appropriate constitutive models,setting relevant parameters of pile foundations and engineering geological conditions based on a specific karst pile foundation project;secondly,setting constraints and boundary conditions,performing grid division,and determining calculation analysis;finally,establishing the model of comparative working condition groups according to the research purpose.2.The finite element analysis was conducted with ABAQUS to simulate the displacement process of pile foundations under various karst geological conditions subjected to external forces.3.Data compilation and analysis were completed.Load-displacement curves of pile foundations under different karst geological conditions were compiled.Based on Technical Code for Testing of Building Foundation Piles and the failure mode of pile foundations in simulation,the standard for selecting the ultimate bearing capacity of pile foundations was determined.Ultimate bearing capacities of pile foundations under different working conditions were extracted,organized,and graphed to analyze the influence of different cave parameters on the ultimate bearing capacity of pile foundations.The results indicate that under the same conditions of a single karst cave,square caves exert a greater adverse impact on the ultimate bearing capacity of pile foundations than circular ones.However,when the cave cap thickness reaches 5 times the pile diameter,the impact of cave shape on the pile foundation becomes negligible.As the single-direction size of the karst caves increases,their adverse effect on the ultimate bearing capacity of the pile foundation gradually intensifies.If two karst caves are present at the pile end with centroids at the same elevation,the appearance of a side cave will significantly reduce the ultimate bearing capacity of the pile foundation.The ultimate bearing capacity of the pile foundation when both caves are elliptical is greater than when they are rectangular.If a constant change of single-directional size for the side cave maintains,when the thickness of the cave cap H is ≤3d,the change in cave height will exert a much greater impact on the ultimate bearing capacity of the pile foundation than the change in span;when H is equal to 5d,the influence of the change in the span of side cave on the ultimate bearing capacity of the pile foundation will exceed that of change in the cave height.As the cave spacing increases,the influence of side caves on ultimate bearing capacity gradually decreases;when the spacing reaches five times the pile diameter,this effect can be ignored.This study employs the numerical simulation method with ABAQUS to analyze the ultimate bearing capacity of pile foundations with multiple karst caves,delving deeper into the influence of geometric characteristics of side caves and cave spacing on the ultimate bearing capacity of pile foundations.It provides theoretical support and technical guidance for practical engineering.Additionally,it offers valuable references and insights for the design and construction of pile foundations under similar complex geological conditions.
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