磁测井法探测灌注桩钢筋笼长度工程应用分析

Engineering ApplicationAnalysis of Magnetic Logging Method to Detect the Reinforcement Cage Length of Cast-in-place Pile

钢筋笼作为灌注桩重要的组成部分,其长度是保证灌注桩承载性能、稳定性能和抗震性能的关键指标之一。灌注桩属于地下隐蔽工程,难以开挖验证钢筋笼长度是否符合设计要求,且其属于典型的铁磁性物质,受地磁场磁化作用后可产生异于背景磁场的磁场信号。本文基于钢筋笼受地磁场磁化作用影响的异常特征,结合模型桩试验和工程桩试验,开展了灌注桩钢筋笼长度磁测井法探测技术研究。探测结果表明,磁测井法探测钢筋笼长度作为对桩基础无损检测的一种方法是可行的;灌注桩钢筋笼长度存在有效的探测范围,在探测孔距为1.0m以内时,可有效探测出钢筋笼底端磁场特征信号;对于超长桩,探测孔垂直度偏差难以控制,垂直度偏差过大,会导致探测孔距远离桩基侧,影响钢筋笼底端磁场特征信号探测结果,实际工程中要尽可能使探测孔紧挨桩基边缘侧钻取。本文通过模型桩和工程桩探测试验,验证了磁测井法探测灌注桩钢筋笼长度的可靠性和有效性,为灌注桩钢筋笼长度探测提供了技术指导。

The reinforcement cage length is one of the key indicators to ensure the bearing performance,stability and seismic performance of cast-in-place pile.The cast-in-place pile belongs to underground concealed works,so it is difficult to verify whether the reinforcement cage length meets the design requirements by excavation the reinforcement cage is a typical ferromagnetic material,which can produce magnetic field signal different from the background magnetic field after being magnetized by the geomagnetic field Based on the abnormal characteristics of reinforcement cage magnetized by geomagnetic field combined with the model pile and engineering pile test,the research on the magnetic logging method for detecting the reinforcement cage length was carried out.The results showed that it was feasible to detect the reinforcement cage length by Magnetic Logging Method as a non-destructive method for pile foundation For the Magnetic Logging Method,there was an effective detection range for the reinforcement cage length When the detection hole spacing was within 1.0 m, the characteristic signal of the magnetic field atthe reinforcement cage bottom could be effectively detected.For the super long pile,the verticality deviation of the detection hole was difficult to control.If the verticality deviation was too large,the detection hole spacing would be far away from the side of the pile foundation, which affected the detection results of the magnetic field characteristic signal at the reinforcement cage bottom In the actual project,the detection hole should be drilled close to the edge of the pile foundation as much as possible. Through the model pile and engineering pile detection test, this paper verifies the reliability and effectiveness of Magnetic Logging Method in detecting the length of reinforcement cage of cast-in-place pile,and provides technical guidance for the detection of the reinforcement cage length of cast-in-place pile.