海相软土对刚性桩复合地基的影响机理分析
摘要:海相软土特性对刚性桩复合地基形成有很大影响,但其影响机理尚不够清晰,工程实践中常被工程相关人员所忽略,造成大量的工程质量问题。依托多个近年来典型工程实例的综合分析、研究成果,主要研究了海相软土的固结沉降、结构性、低渗透性等特性对刚性桩复合地基的影响机理。结合多个工程事故实例的计算分析及现场实测数据,佐证了研究成果的合理性。研究结果认为,海相软土地区刚性桩复合地基应用时,必须充分考虑海相软土固结沉降、高灵敏度、挤土施工扰动等特性的影响,并经现场试验性施工,明确处理效果后方可实施,否则不应直接采用。由于桩端持力层不同,固结沉降引起两种典型复合地基破坏模式:如果桩端悬浮在软土层中,桩端将发生显著的向下刺入变形,桩间土发生塑性变形;如果桩端落在硬土层上,桩体将先发生强度破坏,然后桩间土破坏;宏观上则表现为复合地基沉降长期不收敛甚至出现加速下沉。因挤土施工扰动影响,被基桩挤排的海相软土可视为流体,利用流体总是向最小阻力路径流动的性质,分为三种不同排土路径:沿桩侧塑性区向上排土、沿场地内整体向上排土、沿场地周边薄弱处侧向排土。由于桩间海相软土地基承载力很低,在上部荷载作用下应保证有足够的土拱高度。提出了海相软土地区刚性桩复合地基工程实践中的应对措施及建议。
Abstract:Rigid pile composite foundation is greatly influenced by soft marine clay.But it is neglected by many engineers due to the unclear influence mechanism,which causes serious engineering accidents.Based on the comprehensive analysis and research results of typical construction examples in recent years,the characteristics of consolidation settlement,structure and low-permeability of marine soft soil and the mechanism of rigid pile composite foundation influenced by the soft marine clay were researched.In combined with computational analysis of several construction examples and its field test data,the rationality of research conclusions is verified.The results prove that rigid pile composite foundation should not be directly used in marine soft soil.It is necessary to fully consider the influence of consolidation settlement,high sensitivity,compacting disturbance,and clear treatment effect after the field test construction.There are two different failure mode of composite foundation caused by consolidation settlement due to the different bearing stratum of the pile tips.If pile tips are suspended on the soft soil layer,it causes significant penetrating deformation of pile tips and plastic deformation of the soft soils among piles;if pile tips are embed into the harder soil layer,pile bodies would firstly be destroyed by strength failure and then soft soils among piles would be destroyed.The settlement soils of composite foundation do not converge for a long time and even accelerate subsidence in macroscopically.Because of the disturbance of construction,the marine soft soil pushed by foundation piles could be regarded as fluid.According to the property that the fluid always flows to the path with the least resistance,there are three different soil discharge paths: soil discharge upward along the plastic zone at the pile side,soil discharge upward along the whole site,and soil discharge laterally along the weak area around the site.Since the bearing capacity of marine soft soil foundation between piles is very low,sufficient soil arch height should be ensured under the action of upper load.Finally,the countermeasures and suggestions in the engineering practice of rigid pile composite foundation in marine soft soil area are proposed.
中文标题：
海相软土对刚性桩复合地基的影响机理分析
Mechanism of Rigid Pile Composite Foundation Influenced by Marine Soft Soil
作者：
林志强1,2
Lin Zhiqiang1,2
作者简介:林志强,男,1986年生,汉族,福建漳州人,硕士,工程师,主要从事软土地基处理及边坡、基坑、桩基工程等方面的设计、施工及研究工作。E-mail:zhiqiang_lin@126.com
通讯地址：
1. 福建省建筑科学研究院有限责任公司, 福建福州 350025; 2. 福建省绿色建筑技术重点实验室, 福建福州 350025
1.FujianAcademyofBuildingResearchCo.,Ltd.,Fuzhou350025,Fujian,China; 2.FujianKeyLaboratoryofGreenBuildingTechnology,Fuzhou350025,Fujian,China
中图分类号:TU471.8
doi:10.3969/j.issn.1007-2993.2019.06.005
出版物：岩土工程技术
收稿日期:2019-08-26
网络出版日期:2021-07-06
关键词:海相软土,复合地基,固结沉降,土的结构性,施工扰动,土拱高度
Key words:marine soft soil,composite foundation,consolidation settlement,soil structure,construction disturbance,soil arch height
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基金项目：
基金项目: 福建省自然科学基金资助项目(2019J05129)
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