钻孔灌注桩桩端破坏模式及极限承载力研究

在Mindlin解的基础上,采用数值积分的办法,计算了桩端的应力状态。根据莫尔-库仑破坏准则得出了桩端的破坏面形状以及极限端阻力。并具体分析了桩端破坏面形状以及极限端阻力与桩长、桩径、土性等因素的关系:桩端埋深越大,桩端破坏面稍偏大,对应的极限端阻力越大;桩径越大,破坏面越大,但是,桩端极限承载力却越小;内摩擦角越大,破坏面越大,桩端极限承载力也越大;粘聚力越大,破坏面越小,桩端极限承载力越高;泊松比越大,破坏面越大,桩端极限承载力越大。拟合了一个包含上述影响因素在内的极限端阻力简化公式。最后通过一些工程实测结果分析出了经验系数的取值范围。

Study on Failure Mode and Ultimate Bearing Capacity of Drilled Pile Tip

Based on mindlin solution,stress condition of pile tip was calculated using numerical integration.Failure surface shape of pile tip and ultimate tip resistance was obtained according to Mohr-Column failure criteria.Moreover,relationship among failure surface shape of pile tip,ultimate tip resistance,and pile length,pile diameter,soil characters and so on.The deeper the depth of pile tip is embedded,the bigger the failure surface is and the greater the ultimate tip resistance is.The bigger the pile diameter is,the bigger the failure surface is but the less the ultimate tip resistance is.Failure surface enlarges and ultimate tip resistance increases if internal friction angle increase.The bigger the soil cohesive strength of pile tip is,the smaller the failure surface is but the greater the tip resistance is.Poisson's ratio increase,failure surface enlarges and ultimate tip resistance increases.A simplified formula which contains influencing abovementioned factor was given.At last,some pile test results were used to obtain variety range of construction coefficient.