跨孔超高密度电阻率CT法在建筑物旧有桩基探测中的应用研究

目前,地铁隧道下穿已有建筑物桩基础的工程越来越多,探测和确定桩基参数是隧道施工的首要任务。针对建筑物旧有桩基及障碍物探测,常规地面物探技术很难保证探测的精确性,且物探方法应用较少,本文采用跨孔超高密度电阻率CT法研究建筑桩基的人工宜流电场分布规律与特征。首先简述了超高密度电阻率CT法的原理及技术蒔点,对不同尺寸的单桩、多桩桩基进行地电模型的数值模拟。然后将跨孔超高密度电阻率CT法应用在深圳市地铁9号线泥红区间下穿九明大厦桩基探测中,把观测结果进行数值滤波和反演计算,求解出桩基础的介电特性探测剖面,并与桩基地电模型的数值模拟结果进行对比和校核,最终确认了旧有桩基的直径和埋深,为地下隧道工程的施工提供了参考和依据。与以往常用的CT法工作不同,本次研究综合运用了现场CT勘测与理论有限元分析手段,将理论解析与工程实际应用相结合,验证了桩基地电数值模拟的有效性,同时解决了工程中桩基尺寸与埋深问题。取得了较好的应用效果,为盾构区间施工提供详细的桩基参数。结果表明,该方法在建筑物旧有桩基探测及障碍物探测中具有一定的应用和推广价值。

Application of Cross-hole Ultra-high Density Resistivity CT Method to Detection of Old Pile Foundations in Buildings

At present,there are more and more subway tunnels under the existing pile foundations.It is the primary task of tunnel constructions to detect and determine pile foundation parameters.In view of the old pile foundation detection and obstacle detection of buildings,the conventional ground geophysical technology is difficult to guarantee the accuracy of detection,and the application of geophysical methods are less.In this paper,the cross-hole ultra-high density resistivity CT method is used to study the distribution law and characteristics of the artificial DC electric field with the pile foundation of the building.In the beginning,the principle and technical characteristics of the ultra-high density resistivity CT method are briefly described,and the numerical simulation of the geoelectric model for single-span and multi一pile pile foundations with different sizes is carried out.Then the cross-hole ultra-high density resistivity CT method is applied to the pile foundation detection of Jiuming building under the mud red section of Shenzhen metro line 9,and the observation results are numerically filtered and inversely calculated to solve the dielectric of the pile foundation.The characteristic detection profile is compared and checked with the numerical simulation results of the pile base electrical model.The diameter and depth of the old pile foundation are finally confirmed,which provides a reference and basis for the construction of the underground tunnel project.Different from the CT work commonly used in the past,by using the on-site CT survey and theoretical finite element analysis method and combining the theoretical analysis with the practical application of the project,this research has verified the effectiveness of the electric simulation of the pile foundation,sovled the problem of the size and depth of the pile foundation in the project,and achieved good application results,providing detailed pile parameter foundation for shield construction.It turns out this method has certain application and promotion value in the old pile foundation detection and obstacle detection of buildings.