桩端岩土差异对超长桩影响的对比研究  

CONTRASTIVE STUDY ON INFLUENCE OF DIFFERENCE OF PILE END ROCK-SOIL LAYER ON SUPER-LONG PILE

作　　者：蒋建平[1] 汪明武[2] 高广运[3] 

机构地区：[1]上海海事大学交通运输学院管理系,上海200135 [2]合肥工业大学建筑工程学院 [3]同济大学地下建筑与工程系,上海200092

出　　处：《岩石力学与工程学报》2004年第18期3190-3195,共6页Chinese Journal of Rock Mechanics and Engineering

基　　金：安徽省自然科学基金(01045409)资助课题。

摘　　要：分析了3种类型桩端岩土有差异的8根超长灌注桩的对比试验资料,包括进入基岩和不入基岩的对比试验桩各1根,桩端有沉渣和无沉渣的对比试验桩各1根,桩端沉渣厚度不同的对比试验桩各1根,桩端有无高压注浆的对比试验桩各1根。分析结果表明,桩端岩土由软层转向硬层时,超长桩的荷载-沉降曲线会由陡直转向平缓,极限状态时的破坏由趋于刺入破坏转向趋于整体剪切破坏,桩型由纯摩擦桩转向端承摩擦桩,说明桩端岩土特性对超长桩的承载性状有大的影响;桩端岩土由软层转向硬层时,桩极限承载力的提高主要体现在极限端阻力的提高,极限端阻力的提高可用含端阻力增强系数的公式来表示;桩端高压注浆超长桩还可看成是超长扩底桩,它的极限端阻力除可用端阻力增强系数表达外,也可暂用一般扩底桩极限端阻力的形式来表达;入硬层超长桩(如长径比为82时)还可是端承摩擦桩,它具有很大的承载潜力,一般认为其端阻力小是因为取的桩顶沉降值过于保守造成的。对入硬层超长桩取较大桩顶沉降值时的桩承载力是可行的,此时只要把相邻桩基础的沉降差控制在一定的范围内,使之不产生过大的不均匀沉降即可。Analysis is made on three types of contrastive tests of 8 super-long cast-in-situ piles with different rock-soil layers at pile end. The piles for contrastive tests are 2 piles plunged into and not into bed-rock,2 piles with and without residua at end,2 piles with residua of different thickness,and 2 piles with and without end postgrouting. The study results are as follows. (1) When pile end rock-soil strata changes from soft to dense,the load-settlement curves change from steep shape to gentle one,the failure changes from plunge failure to integer shear failure,the increment of ultimate bearing capacity consists of the increment of ultimate end resistance,and the kind of pile changes from friction pile to end resistance pile,which indicates that end rock-soil layer has significant influence on behavior of super-long pile. (2) The super-long pile with end postgrouting can be regard as super-long pile with pedestal,so that the ultimate end resistance can be expressed by formula including a parameter of resistance increment,and it can also be expressed by the formula of ultimate end resistance for common pile with pedestal. (3) The super-long bored piles,i.e. the pile with length-diameter ratio of 82,penetrating dense stratum,can be regard as end-bearing friction piles with great potential bearing capacity. It is reasonable to confirm bearing capacity of this kind of pile with greater pile head settlement,and this is practicable as long as unbalance settlement is controlled in a limited range.

关 键 词：土力学 超长灌注桩 端阻力 荷载 对比试验 

分 类 号：TU473.14[建筑科学—结构工程]