微测井电法在基坑围护防渗检测中可行性研究

Feasibility study on micro-well logging method in impervious testing of foundation pit retaining structure

为了有效地检测基坑围护结构的渗漏隐患,保证基坑施工安全,以电极管探测理论为理论基础,推导出微测井电法探测范围的理论模型。分别利用AM法与AMN法对现场隔水幕布(研究对象)进行横向裂缝探测与竖向裂缝探测的数值模拟研究,研究结果表明:AM法对横向裂缝的感知能力大于竖向裂缝的感知能力,AMN法对竖向裂缝的感知能力大于横向裂缝的感知能力;分析电极管距、电极极距和裂缝尺寸对微测井电法探测敏感度的影响,研究结果表明:AM装置敏感度主要与电极极距和待测裂缝宽度有关,AMN装置敏感度主要与电极管距和待测裂缝长度有关,并针对工程实际提出参数设置的一般要求,通过物理模拟与工程中的实际应用,验证了微测井电法理论在地连墙防渗检测中的可靠性与准确性,实现了检测过程的等效简化。

In order to effectively detect the hidden faults of the retaining structures of deep foundation pit and ensure the safety of foundation pit,a theoretical model for the detecting range of the micro-well logging were deduced based on the theory of electrode tube detection. The numerical simulation on the detection of transverse cracks and longitudinal cracks were carried out with methods of AM and AMN. The results show that the perceiving ability of AM to transverse cracks is greater than that of longitudinal cracks,the perceiving ability of AMN to longitudinal cracks is greater than that of transverse cracks. The influence of electrode tube distance,the electrode pole distance and crack size on the sensitivity of micro-logging electric detection were analyzed. The results show that the sensitivity of AM device is mainly related to the electrode pole distance and the width of the cracks to be measured,while the sensitivity of the AMN device is mainly related to the electrode tube distance and the lengths of the cracks to be measured. The general requirement of parameter setting is put forward according to engineering practice. The reliability and accuracy of the micro-well logging theory in the seepage detection of the wall were verified through the physical simulation and practical application. The equivalent simplification of the testing process was realized.