静压管桩终压力与极限承载力的相关关系研究  

Relationship between terminative jacking force and ultimate bearing capacity of jacked pipe piles

作　　者：张忠苗[1] 刘俊伟[1] 俞峰[1,2] 张乾青[1] 张明义[3] 

机构地区：[1]浙江大学软弱土与环境土工教育部重点实验室,浙江杭州310027 [2]浙江理工大学建筑工程学院,浙江杭州310018 [3]青岛理工大学土木学院,山东青岛266033

出　　处：《岩土工程学报》2010年第8期1207-1213,共7页Chinese Journal of Geotechnical Engineering

基　　金：国家自然科学基金项目(50678086)

摘　　要：静压桩瞬时终压力与极限承载力是不同的概念,从沉桩过程和承载力时间效应两个方面出发,对两者相关关系的机理进行研究,并提出了侧阻退化系数和时间效应系数的概念;基于静载试验的Q–S曲线,采用灰色理论对未达破坏标准的试验桩进行极限承载力的修正,修正值的提高幅度随静载试验最终沉降的增大而减小;对近2000根静压混凝土管桩的实测数据进行研究,并与其它地区的相关资料展开对比。分析发现承载力与终压力比值(压力比)的概率点呈F分布,压力比随长径比的增加呈双曲线型增长,回归分析得出不同地质条件下的函数表达式。持力层为黏性土时压力比随长径比的增长幅度明显大于其它土层,而在持力层和长径比相同的情况下,桩侧为粉土时的压力比值通常大于黏性土和软土。桩身较短时极限承载力可能小于终压力,主要归因于压桩结束后桩端土体的回弹和应力的释放。The mechanism of the relationship between the ultimate bearing capacity and the terminative jacking force is studied from two aspects of pile installation process and time-effect,in which the concept of friction fatigue coefficient and time-effect coefficient is demonstrated.The ultimate bearing capacity is predicted based on Q-S curve according to the grey theory,and the results are closely related to the final settlement of static load tests.The data of about 2000 jacked concrete piles are studied.It is found that the ratio between the ultimate bearing capacity and the terminative jacking force increases with the ratio between the pile length and the diameter hyperbolically,and is confirmed as F probability distribution.The expressions under different geological conditions are derived by regression analysis.The ratio between the ultimate bearing capacity and the terminative jacking force increases more rapidly when the bearing stratum is cohesive soils than others,and this ratio of the pile in silt is usually larger than that in other soils with the same bearing layer and shape.The ultimate bearing capacity will be smaller than the terminative jacking force of jacked piles with small length,which attributes to the resilience and stress release of the soils around pile tip after construction.

关 键 词：静压桩 极限承载力 最终压桩力 灰色理论 回归分析 

分 类 号：TU473[建筑科学—结构工程]