声波法检测软土地区灌注桩的完整性研究

Research on the Integrity of Cast-in-place Pile in Soft Soil by Sound Wave Method

研究目的:某软土地区新建铁路桥梁的灌注桩,其完整性采用声波法检测。据声波法检测的缺陷异常特征判断的不合格桩,对其进行钻芯及开挖验证,发现声波法检测缺陷性质特征分别为桩周严重缩径、桩半边夹泥、桩全断面夹泥,本文就声波缺陷异常特征与缺陷性质特征的关系展开研究,为不合格桩进行工程处理确定方案,并分析原因改进施工措施,使所有灌注桩一次施工均达到Ⅰ类合格桩。研究结论:(1)软土地区桥梁灌注桩施工时受地下水影响,易塌孔、涌孔,桩底有沉渣,采用声波法的平测、斜测相结合进行完整性检测;(2)声波速度大于完整桩声波速度的85%的桩,为Ⅰ、Ⅱ类合格桩;(3)夹泥露筋桩声波速度仅为完整桩声波速度的70%～85%,且桩中心混凝土较致密,随着时间的推进,钢筋锈断,桩的有效截面积减小,耐久性、承载力、抗剪力均降低,为明显缺陷Ⅲ类不合格桩;(4)严重塌孔、严重水平涌孔、桩底沉渣使声测管有效时间内接受不到声波信号,为桩近全断面夹泥呈断桩,为严重缺陷Ⅳ类不合格桩;(5)上述缺陷如在桩浅部做接桩处理、在桩深部做重新施工或进行水泥注浆,达凝期后采用声波检测合格后,方可定为Ⅱ类合格桩;(6)本研究成果可为铁路、公路等领域软土地区声波法检测桥梁灌注桩的完整性研究提供参考。

Research purposes： In a soft soil area, the cast -in -place pile of a new railway bridge is built. The integrity of the pile is detected by sound wave method. The unqualified pile, which is judged by the characteristics of the flaw detection by acoustic method, is verified by core drilling and excavation. It is found that the properties of the acoustic detection defects are the serious shrinkage of the pile, the half edge of the pile with mud and the whole section of the pile with mud. The relationship between the characteristics of the defects and the nature of the defects is used to deal with the unqualified piles to confirm the plan, and the reasons for the improvement of the construction measures are analyzed, so that all the cast- in- place piles are all built up to class Ⅰ qualified piles. Research conclusions： （ 1 ） In the soft soil area, the construction of bridge cast - in - place piles is influenced by underground water, collapsing holes and gushing holes, and sediment at the bottom of piles. （2） The pile with acoustic velocity greater than 85% of the acoustic velocity of the intact pile is the type I and II qualified piles. （3） The acoustic velocity of the pile with mud is only 70% - 85% of the sound velocity of the complete pile, and the concrete of the pile center is more compact, and the effective section area of the pile decreases with the process of time, and the durability, bearing capacity and shear force are reduced, which is an obvious defect type Ⅲ unqualified pile. （4） Serious hole, serious horizontal gushing hole and pile bottom sediment make the sound measuring pipe not receive acoustic signal in the time window when the acoustic tube is effective. It is a broken pile in the near full section of the pile, and it is a serious defect type Ⅳ unqualified pile. （5） If the above defects are handled in the shallow part of the pile, such as re - construction or cement grouting in the deep part of the pile, and sound wave detection is qualified after reaching the coagulation period, the qualified pile can be determined as classⅡ qualified pile. （6） The research results can be applied for the investigation of the integrity of bridge cast - in - place piles by acoustic wave method in soft soil areas of railways, highways and other fields.