静压桩残余应力的长期观测性状  

Observed long-term behavior of residual stress in jacked pile

作　　者：俞峰[1] 谭国焕[2] 杨峻[2] 李启光[2] 

机构地区：[1]浙江理工大学建筑工程学院,杭州310018 [2]香港大学土木工程系

出　　处：《岩土力学》2011年第8期2318-2324,共7页Rock and Soil Mechanics

基　　金：浙江省自然科学基金项目资助(No.Y1090610)

摘　　要：静压桩施工过程中,可能会沿桩身形成很大的残余应力。通过在砂性土中1根长约26 m静压桩的原位试验,观测了沉桩结束后的残余应力在后续的循环载荷试验、3根邻桩顺次压入、第2次载荷试验以及较长静置期内的长期变化情况,试验历时约212 d。结果显示,循环载荷试验加载水平与循环次数的增加会造成残余应力的进一步累积。邻桩压入使既有桩残余压应力减小,与邻桩即时贯入深度一致的桩身残余应力测点受其影响最明显。桩身残余应力在长时间内会逐步消散至某一稳定值,其时间效应主要与砂性土的蠕变有关,它使得桩周土的土拱效应减弱,并使桩端土的接触压力减小。Significant residual stress may be formed along a jacked pile during installation. Field tests are conducted on a 26 m pile jacked into sandy soil, involving observations on the variations in residual stress in a 212 d test period after pile construction. The test scheme includes a cyclic loading test, installation of three adjacent piles, a reloading test and a relatively long-term rest. The results show that the residual stress of pile is further accumulated in the cyclic loading tests as the number of loading cycles and the level of cyclic loading increase. The magnitude of residual stress, however, is reduced by the tensile effect of jacking the adjacent piles. Such effect is found to be the maximum when the penetrating pile tip approaches the observed depth. The residual stress of pile tends to decay to a stable value for a relatively long period. The influence of time on the residual stress of pile is mainly related to the creep behavior of sandy soil that weakens the soil arching effect around pile and reduces the contact pressure at the tip of pile.

关 键 词：静压桩 残余应力 现场试验 时间效应 蠕变 

分 类 号：TU473.1[建筑科学—结构工程]