基于三维扫描技术的大直径随钻跟管桩基础失效机理研究

Employing Drilling with PHC pipe Cased pile (DPC) technique, large-diameter PHC piles can be embedded in moderately and slightly weathered rock with the drilling borehole. Grouting the gap between the PHC pile and borehole forms an environment-friendly pile foundation with no mud emissions. Firstly, this project is devoted to research on the shear deformation and slippage failure mode of the cement paste/ soil interface and their associated factors by indoor model experiments, to establish a nonlinear constitutive relation of cement-soil interactions and shear deformation. Then, we will develop a experimental method to measure the roughness of the paste/ soil interface by 3D pile scanning technology and establish corresponding experimental platform. Finally, according to the geometry model reconstructed by 3D scanning results from field experimental piles and the constitutive relation of cement paste/ soil interface established by indoor model experiments, the relation between the cement paste/ soil interface roughness and the failure mechanism of large-diameter PHC piles with DPC technique is established by 3D fine modeling and simulation analysis of the pile failure mode under different ultimate load, which provides reliable theoretical basis for the design, promotion and application of large-diameter PHC piles with DPC technique, and further expands the scope of PHC piles with high bearing capacity.

嵌入中、微风化岩的大直径随钻跟管桩是利用专用桩机在成孔的同时沉入大直径PHC管桩，桩端到达持力层标高后再桩侧注水泥浆形成的一种无泥浆排放的环保型管桩基础。本项目首先通过室内模型试验，研究大直径随钻跟管桩外壁水泥浆体-土体胶结面的剪切变形、滑移破坏模式及其影响因素，建立水泥浆土体胶结面耦合作用力与剪切变形的非线性本构关系。其次，建立一套通过三维扫描技术测量水泥浆土体胶结面粗糙度分析方法，并搭建相应实验平台。最后，根据现场原位试验桩的三维扫描结果重构胶结面的几何模型和模型试验所建立的胶结面本构关系，通过三维精细化建模仿真分析不同极限荷载作用下，大直径随钻跟管桩的失效破坏模式，从而建立粗糙度因子与大直径随钻跟管桩失效机制的关系。为大直径随钻管桩的设计及其推广与应用提供可靠的理论依据，进一步拓展大直径高承载力PHC管桩的应用范围。

项目以桩侧后注浆随钻跟管桩的失效破坏机理为研究目标，开展了一系列室内外试验、理论及数值模拟研究，深入揭示了管桩-注浆体-土体的接触界面剪切滑移破坏特性。首先，开展了大型桩侧注浆前后的桩-土接触界面剪切试验，并运用三维激光扫描技术构建了精细化的注浆界面精细化三维构造模型；随后，结合桩侧注浆液流动特性、出浆口布置方式、注浆压力变化等影响因素试验分析，建立了各因素下管桩-注浆体-土体的界面粗糙度提取方法与精细化有限计算模型；最后，结合现场原位静载与高应变承载力测试结果，不仅优化了随钻跟管桩的桩侧注浆工艺，还提出了注浆前后桩侧摩阻力的转换关系式与桩基承载力设计计算方法。项目共发表学术论文11篇，其中SCI收录2篇、EI收录3篇；申请相关专利14件，授权专利10件，其中授权发明专利4，授权实用新型专利6件；培养了博士后4名，硕士4名；组织及参加国内外学术会议9次，大会邀请报告3个。相关研究成果已应用于广州市白云区沙亭岗深基坑支护工程，以及珠海格力商业地块上覆深厚淤泥层嵌岩大直径管桩基础工程。本项目完成了计划书的全部考核指标，研究成果为大直径随钻跟管桩的施工工艺、设计方法及工程应用经验提供了重要的技术支持。

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