被动桩中土拱效应特征与影响参数研究

采用平面有限元方法,对被动桩在粘性、无粘性土体条件下的土拱形成机理进行了分析。从土拱效应的4个主要方面:土拱形状、桩周土体塑性(拉裂)区的分布、竖向位移等值线及桩后土体残余荷载分担比,探讨了改变桩、土参数,如粘聚力、内摩擦角、弹性模量、泊松比、剪胀角、桩土接触面特性时,土拱效应的变化规律。研究表明,土性不同时,土拱形成过程中土体的受力和破坏形式不同;泊松比、剪胀角、桩土接触特征对土拱效应的影响最明显;强度高、剪胀角大、桩土接触面粗糙或泊松比小的土体,易形成土拱。根据研究结果,指出Tom io Ito排桩塑性绕流土压力理论计算公式尚存不足。

BEHAVIOR OF SOIL ARCHING BETWEEN PASSIVE PILES AND EFFECTS PARAMETERS STUDY

Few studies have been conducted on the mechanism and behavior of soil arching surrounding passive piles.In this paper a plane FEM is applied to assess four key factors of soil arching,such as its shape,the vertical displacement contour,plastic or tensile area of soil surrounding piles and residual stress post piling.Changes in cohesion,internal friction angle,elastic modulus,Poisson ratio,dilatancy angle,and interface conditions are evaluated respectively.The results indicate that the yield mechanisms of cohesive and non-cohesive soils around piles are different when forming the soil arching.Poisson ratio,dilatancy angle,and interface conditions play very important roles in soil arching effects.The results also demonstrate effects of interaction of pile and lateral soil movements,relationship between bypassed earth pressure around piles and soil parameters,and the discrepancy of Tomio Ito’s earth pressure formula.