软黏土中双排微型桩围护结构的开挖过程性能分析  

EXCAVATION-INDUCED BEHAVIOR OF A RETAINING STRUCTURE USING DOUBLE-ROWED MICROPILES IN SOFT CLAY

作　　者：俞峰[1] 刘念武[2] 房凯[2] 

机构地区：[1]浙江理工大学建筑工程学院,浙江杭州310018 [2]浙江大学岩土工程研究所,浙江杭州310058

出　　处：《岩石力学与工程学报》2013年第S2期4139-4148,共10页Chinese Journal of Rock Mechanics and Engineering

基　　金：浙江省公益技术研究项目(2011C33011);住房和城乡建设部科技项目(2011–K3–34)

摘　　要：双排微型桩围护结构兼具施工便利和侧向刚度高的优点。为获知其原位工作性能,在软黏土场地内施工88根微型桩构成双排桩围护结构,通过测斜管、土压力盒、钢筋应力计等量测单元测定挖土过程中的围护结构工作性状。试验结果结合数值分析后发现,随着开挖深度的增加,桩身最大位移不断增大,且最大位移处位于开挖面附近。桩顶能够承受一定的弯矩且弯矩值大小与开挖深度相关,同时桩身弯矩的分布与开挖深度有关。后排桩所受土压力可以通过冠梁和桩间土传递到前排桩上,随着开挖深度的增加,桩间土压力在开挖面上部呈减小趋势,在基坑底以下呈增大趋势,其实测值介于体积比例系数法和弹性地基梁法计算值之间。后排桩所受主动土压力、基坑底部所受被动土压力和桩身位移有关,被动区的实测土压力和弹性地基梁法计算值比较接近。Double-rowed micropiles,usually served as excavation-supporting structures,have advantages such as convenient construction and satisfying lateral stiffness. In order to provide better understanding of their field performance,we investigate a full-scale retaining structure with 88 micropiles arrayed in two rows. The structure is instrumented to measure the lateral displacement,earth pressure and pile stress during excavation. The field-test results and associated numerical analyses show that the displacement of pile shaft increases with the increasing excavation depth and the maximum displacement is captured near the excavation surface. A non-zero bending moment is recorded at the pile head and the excavation depth decides the magnitude and distribution of the bending moment. The earth pressure imposed on the back-row piles can be transferred to the front ones through the upper connecting beam and the soil between the two pile rows. As the excavation proceeds,the earth pressure between the two pile rows decreases gradually above the excavation surface but increases below the surface. The measured pressures lie between the results calculated by the volume-scaling factor method and the elastic foundation beam method. Furthermore,both the active earth pressure acted on the back-row piles and the passive pressure at the bottom of pit are related to the displacement of pile shafts. The measured passive earth pressure is in good agreement with the predicted value of the elastic foundation beam method.

关 键 词：桩基础 双排微型桩 软黏土 原位试验 土压力 桩土相互作用 

分 类 号：TU473.1[建筑科学—结构工程]