粉土地基中劲性复合桩抗压承载特性与荷载传递机制研究  

Compressive bearing capacity and load transfer mechanism of stiffened deep cement mixing pile installed in silt

作　　者：文磊 刘钟 马晓华 张振[3] WEN Lei;LIU Zhong;MA Xiao-hua;ZHANG Zhen(Zhejiang Kunde Innovate Geotechnical Engineering Co.,Ltd.,Ningbo,Zhejiang 315100,China;Kunde Research Institute of Intelligent GeotechnicalTechnology,Ningbo,Zhejiang 315100,China;Department of Geotechnical Engineering,Tongji University,Shanghai 200092,China)

机构地区：[1]浙江坤德创新岩土工程有限公司,浙江宁波315100 [2]坤德智慧岩土技术研究院,浙江宁波315100 [3]同济大学地下建筑与工程系,上海200092

出　　处：《岩土力学》2024年第2期511-524,共14页Rock and Soil Mechanics

摘　　要：劲性复合桩(stiffened deep cement mixing pile,简称SDCM桩)兼具高强度芯桩的轴向荷载传递能力与搅拌桩较高的桩侧摩阻力优势,施工效率高、性价比高,在土木建筑领域中得到推广应用。然而,由于其荷载传递机制尚缺乏统一认识,现有计算方法与实测承载力差异较大。基于此,开展了粉土地基中SDCM桩现场足尺试验,研究了其抗压承载特性与荷载传递机制。搅拌桩固化剂采用普通水泥和GS固化剂(gypsum-slag soil hardening agent)。依据实测荷载-位移曲线分析了单桩抗压极限承载力及不同固化剂的影响,并通过现场桩身取芯及芯样无侧限抗压试验分析了现场施工水泥土与室内试样强度的差异。建立了考虑芯桩-水泥土、水泥土-土体接触面的三维弹塑性有限元模型,分析了竖向下压荷载条件下桩身轴力、接触面的剪切应力分布规律,探讨了SDCM桩的荷载传递机制与承载力提高原因。研究结果表明:粉土地基中SDCM桩抗压承载力大于纯搅拌桩和单独芯桩抗压承载力之和的1.5倍;在端阻力发挥作用后,桩底水泥土由于轴向受压变形,芯桩-水泥土之间的剪切变形会大幅增加,该位置易产生剪切破坏。水泥土固化后与地基土接触面性能的改善是SDCM桩相对传统灌注桩具有更高的承载力的主要原因。Stiffened deep cement mixing(SDCM) pile are gaining popularity in civil and architectural engineering due to their combination of core pile advantages,such as high axial load transfer ability,and deep mixing column advantages,such as high side friction.SDCM piles offer high construction efficiency,high bearing capacity,and lower costs.However,the existing calculation methods for determining their bearing capacity often differ significantly from actual test results due to a lack of unified understanding regarding their load transfer mechanism.To address this,full-scale field tests of SDCM piles embedded in silt were conducted to study the compressive bearing characteristics and load transfer mechanism.Ordinary cement and gypsum-slag soil hardening agent were both used as the binder materials in SDCM pile.The pile load-displacement curves were measured,and the ultimate bearing capacity of a single SDCM pile under compression was analyzed.The influence of binder materials was also checked.Coring tests were conducted to obtain its unconfined compressive strength(UCS).The discreteness of UCS between the field mixing cemented soil and the laboratory test were also analyzed.A three-dimensional elastoplastic finite element numerical model considering the interfaces of core pile-cemented soil and cemented soil-in-situ soils was established.The distribution of axial force along pile shaft and the shear stress between contact surfaces under different loads applied to the pile head were explored.The load transfer mechanism was analyzed and the higher bearing capacity compared with bored piles were discussed.The results show that the ultimate compressive bearing capacity of the SDCM pile in silt is larger than 1.5 times the sum of the compressive bearing capacity of the pure deep mixing pile and the single core pile.As the end resistance takes effect and increases,the shear deformation between the core pile and the cemented soil at the pile tip will increase rapidly due to the axial compression of the cemented soil.Thus,this

关 键 词：劲性复合桩 粉土地基 抗压承载力 现场试验 数值模拟 

分 类 号：TU47[建筑科学—结构工程]