灌注桩后注浆对桩周黄土力学特性和湿陷性的影响

为了降低新疆地区黄土湿陷变形对该地区特高压输电线路塔基基础稳定性的影响,文章以新疆伊犁哈萨克自治州尼勒克县塔勒德地区的黄土为研究对象,采用灌注桩后注浆工艺对黄土地基进行改良,通过直剪试验、湿陷性测试、场发射扫描电子显微镜(field emission scanning electron microscope, FESEM)观测和X射线衍射(X-ray diffraction, XRD)分析等方法,探究灌注桩后注浆对桩周黄土力学特性、湿陷性指标和微观结构特征的影响。结果表明:灌注桩后注浆后,桩周黄土内摩擦角由改良前的23.66°增大为26.76°,增幅为13.10%;黏聚力由改良前的20.88 kPa增加至31.30 kPa,增大49.90%;改良后较改良前黄土的湿陷系数平均下降0.026左右,湿陷系数下降明显,说明后注浆方法可以改善黄土的湿陷变形问题。

To mitigate the impact of the collapsible deformation of loess on the stability of the tower foundation of the ultra-high voltage transmission lines in Xinjiang, the loess from Talede area of Nilka County, Ili Kazakh Autonomous Prefecture, Xinjiang was investigated using experimental method. The loess foundation was improved by the post-grouting process of cast-in-place piles. Effects of post-grouting of cast-in-place piles on the mechanical properties, collapsibility indexes and microstructure characteristics of loess around the piles were analyzed using the direct shear test, collapsibility test, field emission scanning electron microscope (FESEM) observation and X-ray diffraction (XRD). The results show that the post-grouting method of cast-in-place piles increases the internal friction angle from about $ 23.66^{\circ} $ to $ 26.76^{\circ} $, with an increase of 13.10%. The cohesion force increases from about 20.88 kPa to 31.30 kPa, with an increase of 49.90%. After the post-grouting improvement, the coefficient of collapsibility of loess decreased by about 0.026 on average compared with original coefficient of collapsibility. The coefficient of collapsibility decreases obviously, which indicates that the post-grouting method can mitigate the collapsible deformation of loess.