Load-Bearing Characteristics Analyzing On Varingarea Pile Formed After Wall Of Pile Foundation Hole Collapsed

Hole wall collapse of pile foundation is a common problem in the construction process; and due to nervous construction period, many construction enterprises take a simple way to deal with the hole collapse of pile foundation or not to deal and concrete directly.So a large number of variable cross-section piles emerge; this is a common problem which should not be circumvented. Basing on engineering practice, This paper deals with the study of load-bearing characteristics analyzing on non-uniform piles formed after hole wall of pile foundation collapse by theoretical analysis and ANSYS. Following major elements:1,summarizes the mechanism, Influence factors, therapeutic measures of hole wall collapse and the types and characteristics of variable cross-section and defective piles and other research status both domestic and overseas;2,analyzes the mechanism of Pile with hole collapse, and differences between the straight tapered pile and ordinary similarities piles; discusses the factors related to the stability of the hole wall; and summarizes the main forms of hole wall collapse; and make a slip-line assumptions to the collapse of hole wall.3,deduces the ultimate bearing capacity of single pile with hole wall collapse based on specifications recommended by empirical method; derives formula for the settlement of single pile with hole wall collapse based on layer summation method and make a failure mode of pile foundation hole wall collapse.4,based on the engineering project case and analyzing on non-uniform pile formed after hole wall of pile foundation collapse with the application of ANSYS,relevant conclusions are obtained as follows:(1) expanding diameter is beneficial to settlement of the pile in project practice; but under working load, the effect is not obvious so its role can not be overstated.(2) under vertical load, the axial force decrease suddenly in the depth direction of the regional cross-section region, resulting evident stress concentration at Variable Section, top variable cross-section tripping off soil, tension cracks appearing;(3) With the hole wall collapsing in the different locations, the top displacement of piles varies regularly which is large when collapse point close to ground and relatively small when far from ground.(4) to non-uniformly varying cross-section piles with the hole wall collapsed, under vertical load, tensile stress may emerge in the lower part of the relative orientation of Variable Section, and ultimately lead to buckling failure of the pile material.