BOTDR分布式检测技术在复杂地层钻孔灌注桩测试中的应用研究

BOTDR BASED DISTRIBUTED STRAIN TEST ON BORED PILE BURIED IN COMPLICATED GEOLOGICAL GROUND

采用布里渊光时域反射技术(BOTDR)对灌注桩进行了分布式应变检测,据此计算桩身位移、桩身挠度、桩身轴力、侧摩阻力和桩端阻力等参量,并在一复杂地质条件场地内两种不同长度和工艺类型的灌注桩内力测试中等到应用,测试表明:灌注桩加载过程中,桩身应变分布在塌孔、夹层及地层分界面等部位出现异常;荷载主要由桩身侧摩阻力承担,桩端阻力在试验荷载内都未发挥;桩基承载能力和特性差异主要由施工工艺及地层条件不同所引起。

This paper presents the principals of bored pile test using Brillouin optical time domain reflectometer （ BOTDR ）. The formulas used to calculate the displacement, flexibility, axial force, skin friction and end - bearing resistance of piles were presented. This technique was applied to pile static load tests under complex geological conditions to detect the strains and internal forces in different types of bored piles. The test results indicate that the abnormities of the strain distribution along the piles were found at the positions of hole collapse, weak intercalation, and/or formation interface. On account of the differences of the field conditions and construction techniques, the end- beating resistances didn＇t exert fully; the skin friction served as the main resistance to the loads. The piles beating characteristics were different each other.