Study On Bearing Behavior Of Post-grouting Bored Pile In Loess Area

Super-longhole bored pile are widely used in deep foundation engineeringnowadays， because it could provide relatively large pile carrying capacity， and itcould easily fit for the layer. The author analyzes the load transfer mechanism andbearing feature of large diameter and super-longhole bored pile in Loess area based onpile strain test and static load test of a pile foundation engineering in loess area in orderto draw conclusions useful for engineering practice.Research shows that the curve of super-longhole bored pile in loess area slowlysubsides; it is calculated that the vertical load is mainly provided by shaft resistance，and mainly focuses on middle and upper side of the pile， while the shaft resistance oflower pile is rather small， thus we can conclude that super-longhole pile is typicalfriction pile; the range of relative displacement needed when some lateral resistance ofthe pile reaches limit number is proposed. When the feature of soil is similar， thedeeper the soil is， the larger the relative displacement is needed; the transferring sigmafunction every soil layer fits the hyperbolic curve mode， the transferring sigmafunction of surface soil layer is characterized by manufacturing installation.After comparative and analysis the measured of post-grouting pile， we could seethat applying post-grouting technique could effectively increase load pressure of pileand reduces pile sedimentation. Under the effect of pile top load， the axial force thrustobviously weakens， therefore the effect of the pile side resistance increases， andmainly focuses on the upper side of the pile; while under the effect of limit load， thepile side resistance of post-grouting of upper soil layer of the pile is obviously higherthan that of uncompacted pile， and both are beyond the standard recommended value.The pile side resistance of post-grouting of lower soil layer of pile increases a littlecompared with that of uncompacted pile， and even decreases， the reason is that the pile side resistance of lower part has not exerted， after the design considering thefactors of pile foundation design optimization，such as reducing pile length.