后注浆钢管桩桩-土界面力学特性及微观结构

后注浆微型钢管桩具备施工速度快、布置形式灵活、承载力高等优点,在输电线路基础工程中具有广阔的应用前景.目前有关注浆后桩-土界面力学行为与强度特性尚未得到定量认识,因此,需要开展后注浆钢管桩桩-土界面力学特性及微观结构的试验研究.依托国网沧州东光北变220 kV线路工程,对原状土和不注浆钢管桩、后注浆钢管桩桩侧不同水平距离处土体及桩-土界面进行现场取样,通过室内试验分析了注浆作用对土样变形及抗剪强度参数的影响,借助微米CT扫描仪和扫描电镜(scanning electron microscope,SEM)测试手段,从微观层面对比分析注浆作用下桩-土界面结构的变化及浆液进入原状土体的程度及分布特征.结果表明:注浆后浆液的渗入使得土体结构更加密实且黏聚力明显增大,但浆液影响范围有限.研究成果可为该桩型加固机理的揭示及工程设计提供参考依据.

Study on mechanical properties and microstructure at pile-soil interface of post-grouting steel pipe pile

Post-grouting micro steel pipe pile has the advantages of fast construction speed, flexible layout and high bearing capacity, so it has a broad application prospect in transmission line foundation engineering. At present, the mechanical behavior and strength characteristics of pile-soil interface after grouting have not been quantitatively recognized. Therefore, it is necessary to carry out the experimental research on the mechanical properties and microstructure at pile-soil interface of post-grouting micro steel pipe piles. Relying on Cangzhou Dongguangbei substation 220kV line project to carry out on-site sampling of undisturbed soil and soil at different horizontal distances from the side of non grouting steel pipe pile and post grouting steel pipe pile and the pile-soil interface. The effects of grouting on deformation and shear strength parameters of soil samples were analyzed through laboratory tests. With the help of micro-CT scanner and scanning electron microscope(SEM) testing mrthods, the changes of pile-soil interface structure under grouting and the degree and distribution characteristics of slurry entering undisturbed soil were compared and analyzed. The results show that the infiltration of the slurry after grouting makes the soil structure more compact and the cohesion significantly increased, but the range of influence of the slurry is limited. The research results can provide reference basis for revealing the mechanism of the pile-type reinforcement and the engineering design.