砂土地基小直径单桩的浅层土p–y曲线  

Shallow-layer p-y curves for single micropile in sands

作　　者：王晓伟[1,2] 叶爱君[1,2] 商宇[1,2] WANG Xiao-wei;YE Ai-jun;SHANG Yu(State Key Laboratory of Disaster Reduction in Civil Engineering,Tongji University,Shanghai 200092,China;,Department of Bridge Engineering,Ton~i University,Shanghai 200092,China)

机构地区：[1]同济大学土木工程防灾国家重点实验室,上海200092 [2]同济大学桥梁工程系,上海200092

出　　处：《岩土工程学报》2018年第9期1736-1745,共10页Chinese Journal of Geotechnical Engineering

基　　金：国家自然科学基金项目(51278375);土木工程防灾国家重点实验室项目(SLDRCE 15-B-05)

摘　　要：小直径桩在桩基础的抗震设计、加固中已得到越来越多的应用。针对美国石油协会（API）规范的p–y曲线法和中国规范的m法对小直径单桩的适用性问题,通过拟静力试验研究了砂土地基小直径单桩的浅层土（深度小于1 m）p–y曲线。对实测桩身弯矩采用分段函数的拟合方法来推算土反力和桩身变形,获得了小直径单桩在饱和中砂中的浅层土静力p–y曲线,并基于试验结果提出了三线性本构。进一步地,通过数值模拟分析比较了所提出的浅层土三线性p–y曲线、API规范的p–y曲线、中国规范的m法对预测小直径桩基受力和变形的有效性。结果显示API规范的p–y曲线可能稍低估桩基的水平承载力,并获得更深的桩身最大弯矩位置,而提出的浅层土三线性p–y曲线可更好地预测桩基的整体水平力和位移关系、桩身弯矩及变形。另外,传统的m法仍然适用,当桩身变形较小时（土面桩身变形不超过6 mm）,m值宜取推荐范围内的较大值,而当桩身变形较大时,m值宜取推荐范围内的最小值。Micropiles are increasingly used in seismic design or retrofitting for pile foundations. This study aims to investigate the validity of the widely used p-y relationships proposed by the American Petroleum Institute（API） and the ‘m method＇ in the Chinese Code for numerical modeling of micropiles in sands. A quasi-static test is performed to reveal the shallow-layer（depth less than 1.0 m） experimental p-y curves for the micropiles in saturated medium dense sands. A piecewise-function based p-y derivation method is adopted to develop the experimental p-y curves. Subsequently, trilinear models for the shallow-layer p-y curves are proposed based on the test results. Further, numerical simulation techniques are used to analyze the validity of the proposed trilinear p-y model, API p-y model and ‘m method＇ for predicting the strength and deflection of micropiles in sands. The results show that the API p-y model may slightly underestimate the lateral strength and overestimate the depth-to-maximum bending moment, whereas the proposed shallow-layer trilinear p-y model preferably predicts the global force-displacement relationship, bending moment and lateral deflection of micropiles. In addition, the conventional ‘m method＇ is capable to predict the strength and deflection of micropiles. Specifically, a relatively large m value chosen from the recommended range is reasonable for the situation of deflection of small piles at soil surface（less than 6 mm）, whereas for the micropiles with a relatively large deflection, the smallest m value among the recommended range is a preferable choice.

关 键 词：拟静力试验 小直径桩 p–y曲线 浅层 砂土 

分 类 号：TU473[建筑科学—结构工程]