弱超固结黏土中桩靴贯入形成孔洞对承载力影响  

Effect of cavity on the bearing capacity of spudcan foundation in lightly overconsolidated clay

作　　者：陈洋彬 郑敬宾 王栋 CHEN Yangbin;ZHENG Jingbin;WANG Dong(Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering, Ocean University of China, Qingdao 266100, China;College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China)

机构地区：[1]中国海洋大学山东省海洋环境地质工程重点实验室,山东青岛266100 [2]中国海洋大学环境科学与工程学院,山东青岛266100

出　　处：《海洋工程》2021年第1期112-120,170,共10页The Ocean Engineering

基　　金：国家自然科学基金项目(51809247,U1806230);山东省自然科学基金(ZR2018BEE043)。

摘　　要：自升式平台作业前需对桩靴基础进行预压安装,使桩靴具备抵抗竖向-水平-弯矩复合荷载的能力。安装过程中,桩靴上部将形成一定深度的孔洞。弱超固结黏土地基中,土体强度较高,桩靴最终贯入深度较浅,而形成的上部孔洞较深,因此孔洞将对桩靴就位后的承载力产生影响。通过有限元分析,研究弱超固结黏土中桩靴上部孔洞对承载力的影响,结果表明:1)与无孔洞的情况相比,孔洞的存在对桩靴的单向和复合承载力有削弱作用;2)当桩靴与孔洞底部距离大于桩靴直径时,承载力不再受上部孔洞的影响;3)当桩靴埋深小于等于0.75倍桩靴直径时,无论桩靴上部有无孔洞,现有预测公式都不能较为合理地预测弱超固结黏土地基的复合承载力,为此提出了考虑孔洞影响的桩靴复合承载力包络面预测公式。Before the operation of mobile jack-up rigs,spudcan foundations are routinely preloaded to penetrate into the seabed,in order to provide sufficient bearing capacity under the combined vertical,horizontal and moment loading.During spudcan penetration,a cavity will be formed above the spudcan.In lightly overconsolidated clay,the spudcan will rest at a relatively shallow depth under the final preload,while a relatively deep cavity will be formed above spudcan.Thus,the bearing capacity of spudcan footing may be affected by the cavity.In this study,finite element analyses are performed to investigate the effect of cavity on the bearing capacity of spudcan in lightly overconsolidated clay.The numerical results indicate that:(1)the existence of the cavity results in a decrease in the uniaxial bearing capacity and combined bearing capacity of spudcan,compared with the cases where no cavity is presented;(2)when the distance between the largest cross-section of spudcan and the bottom of cavity exceeds one spudcan diameter,the bearing capacity is no longer affected by cavity;and(3)for spudcan at a depth≤0.75 times spudcan diameter,the failure envelope for spudcan under combined loading in lightly overconsolidated clay cannot be predicted by the existing predictive formulas regardless of the existence of the cavity,and thus an expression that incorporates the effect of the cavity is proposed to formulate the failure envelopes of spudcan under combined loading.

关 键 词：桩靴基础 承载力 复合加载 黏土 孔洞 自升式平台 包络面 

分 类 号：P751[交通运输工程—港口、海岸及近海工程]