砂土各向异性临界状态模型及砂质海床板锚承载特性评价  

Anisotropic critical state model for sand and evaluation of bearing capacity ofplate anchors in sandy seabed

作　　者：王学涛 王立忠[1] 洪义[1,2] 高智伟[3] WANG Xuetao;WANG Lizhong;HONNG Yi;GAO Zhiwei(College of Civil Engineering and Architecture,Zhejiang University,Hangzhou 310058,China;Center for Balance Architecture,Zhejiang University,Hangzhou 310058,China;James Watt School of Engineering,University of Glasgow,Glasgow 311122,UK)

机构地区：[1]浙江大学建筑工程学院,浙江杭州310058 [2]浙江大学平衡建筑研究中心,浙江杭州310028 [3]格拉斯哥大学,格拉斯哥311122

出　　处：《岩土工程学报》2023年第11期2346-2356,共11页Chinese Journal of Geotechnical Engineering

基　　金：国家重点研发计划项目(2018YFE0109500);国家自然科学基金项目(52122906,51939010);浙江省自然科学基金项目(LHZ20E090001)。

摘　　要：砂土组构各向异性及演化显著影响其力学行为,对砂土海床中板锚等承载特性有重要影响。基于各向异性临界状态理论框架(ACST),引入考虑组构各向异性非共轴流动法则,建立了砂土各向异性非共轴模型,并嵌入有限元ABAQUS;通过引入正则化技术,显著降低了砂土应变局部化导致的网格依赖性。基于不同应力路径砂土单元试验和砂土中板锚上拔离心试验,验证了上述模型;探究了不同组构沉积海床(沉积角α0为0°,45°,90°)中平板锚的上拔特性。研究表明:①同一应力水平和密实度下,平板锚的上拔峰值承载力随α0的增大而提高,因为高α0海床中的砂土组构演化更快、导致峰值摩擦角更高。②如忽略组构各向异性影响,并基于三轴压缩数据标定模型参数,可使砂土中板锚承载力高估达100%;因为各向同性模型在满足三轴压缩预测条件下会高估其他路径下(如三轴伸长、单剪)的砂土强度。③传统极限平衡法不考虑组构各向异性,只能合理预测沉积角α0=0°时锚板承载力,但低估了α0为45°,90°时的上拔承载力。The fabric anisotropy and evolution of sand significantly affect its mechanical behavior,and thus play an important role in altering the bearing capacity of foundations(e.g.,plate anchor)in sandy seabed.In this study,an elasto-plastic critical state model for sand considering fabric anisotropy and its evolution along with the non-coaxial plastic flow rule is developed within the framework of anisotropic critical state theory(ACST).The model is then implemented into the three-dimensional finite element program ABAQUS.By introducing the nonlocal plasticity theory,the mesh dependency caused by strain localization of sand is minimized.The predictive capacity of the proposed model is validated through the successful simulation of sand element tests subjected to various stress paths,and the centrifugal model tests on the pull-out behavior of the plate anchor in sand.The effects of fabric anisotropy on the pull-out responses of plate anchors in sandy seabed are investigated via parametric studies,which consider different levels of initial fabric anisotropy(sedimentation angleα0=0°,45°,90°).It is revealed that:(1)For a given stress level and relative density of the sandy bed,the peak pull-out resistance of the plate anchor increases withα0.This is because the fabric of the soil along the sliding wedge(above the anchor)evolves faster at a higherα0 value,leading to a larger peak friction angle.(2)Ignoring the effects of fabric anisotropy leads to significant overestimation(by up to 100%)of the peak pull-out capacity of the plate anchor in sand,because the isotropic model that well predicts the triaxial compression behavior of sand will overestimate the strength of sand under other loading paths(such as triaxial extension and simple shear).(3)The traditional limit equilibrium analysis method does not consider the fabric anisotropy,and can only reasonably predict the pull-out capacity of the anchor plate when the sedimentation angle isα0=0°,but underestimates the scenarios ofα0=45°,90°.

关 键 词：各向异性砂土本构 非共轴各向异性流动法则 正则化技术 有限元模拟 平板锚 承载力 

分 类 号：TU441[建筑科学—岩土工程]