基于现场试验的桩身总侧阻力达到极限后的退化  

DEGRADATION OF PILE TOTAL SKIN FRICTION AFTER REACHING ULTIMATE STATE BASED ON FIELD TEST

作　　者：蒋建平[1] 高广运[2] 章杨松[3] 

机构地区：[1]上海海事大学交通运输学院,上海200135 [2]同济大学地下工程系,上海200092 [3]南京理工大学土木工程系,江苏南京210094

出　　处：《岩石力学与工程学报》2008年第3期633-642,共10页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金资助项目(50678128);上海市教委科研项目(05FZ03);上海市教委交通运输与规划重点学科项目(J50601)

摘　　要：基于40个场地中共82根桩的现场试验资料,通过研究桩身总侧阻力随桩顶沉降的发挥性状发现,桩身总侧阻力达到极限状态的36根摩擦桩中有13根桩的桩身总侧阻力出现退化现象。桩身总侧阻力达到极限后退化的型式主要有4类:退化后保持基本恒定的残余值、退化后一直降低、退化后又有缓慢增加甚至有的呈波浪状、其他特殊类型;超长桩桩身总侧阻力达到极限后退化的桩顶沉降较大(21.34～35.21 mm),非超长桩的较小(4.13～14.19 mm);桩身总侧阻力的退化是桩身各截面侧阻力在桩顶荷载作用下自组织、自调整的结果;描述存在退化的桩身总侧阻力–桩顶沉降曲线的数学模型主要有玻耳兹曼模型、三折线模型;桩身总侧阻力的退化有较大的危害,可采取诸如增强桩侧土强度、增加桩表面粗糙度、使桩进入好的持力层、清除桩端沉渣、事先预压等措施进行防治。研究结果表明,桩身总侧阻力达到极限后退化的探讨对桩承载性状的研究具有重要作用。Based on the field testing data of 82 piles in 40 sites, through the study on the mobilization characteristics of pile total skin friction with pile head settlement, it is found that： （1） the total skin friction of 13 piles degrade in 36 piles whose total skin friction have arrived at ultimate state; （2） there are four types for pile total skin friction＇s degradation, i.e. the pile total skin friction keeps constant residual value, the pile total skin friction decreases continuously, the pile total skin friction increases slowly, and other type; （3） the pile head settlement when the total skin friction degrades for super-length pile is greater（21.34 - 35.21 mm）, while the pile head settlement for short-middle length pile is smaller（4.13 - 14.19 mm）; （4） the degradation of the pile total skin friction is induced by self-organization and self-adjustment of skin friction of all pile sections; （5） the Boltzmann model and three-beeline model can be used to describe different curves of the total skin friction with degradation versus the pile head settlement; and （6） some measures, such as improvement of the degree of roughness of pile surface, can be taken to prevent and prevent the accidents induced by the degradation of pile total skin friction.The following conclusion can be drawn that the research has important significance to the understanding of pile bearing characteristics.

关 键 词：桩基工程 桩身总侧阻力 退化 桩顶沉降 现场试验 极限状态 

分 类 号：TU47[建筑科学—结构工程]