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城市地铁盾构区间孤石的三维定位问题一直未得到很好的解决,为了提高实际工程对孤石异常体的探测识别和定位精度,尝试将三维电阻率跨孔CT精细化探测方法引入到地铁孤石群的探测工作中。首先,从4个平行钻孔“透视对穿”的典型观测模式出发,探讨三维电阻率跨孔CT反演成像方程及适用的装置类型,通过数值模拟研究发现,利用AM-BN电极阵列装置形式采集电位梯度数据得到的孤石成像效果最佳。在此基础上,进一步针对影响探测效果的2个要素——孔距和电极间距开展系统的数值模拟试验研究,据此提出合理的三维电阻率CT探测参数,并检验对小粒径孤石、密集分布的孤石群的识别效果。最后,结合物理模型试验研究进行验证,探测结果较准确地反映了高阻异常的分布情况,表明三维电阻率跨孔CT方法用于地铁孤石探测是可行的。
The three-dimensional localization of boulders in urban metro shield has not been well solved. In order to improve the detection and identification accuracy of boulder anomaly in practical engineering, attempts have been made to introduce the three-dimensional resistivity cross-hole CT refinement detection method into the subway Boulders detection work. First of all, starting from the typical observation mode of four parallel drilling “penetration through the hole”, the three-dimensional resistivity cross-hole CT inversion imaging equation and the applicable device type are explored. By using the numerical simulation, it is found that the AM-BN electrode array Device form acquisition potential gradient data obtained by the best results of solitary bouldering. On the basis of this, a systematic numerical simulation experiment is conducted on two factors that affect the detection effect, such as the pitch and electrode spacing. Based on this, a reasonable three-dimensional resistivity CT detection parameter is proposed, Identification of densely distributed boulders. Finally, the physical model test is used to verify the results. The detection results accurately reflect the distribution of high resistivity anomalies, indicating that the three-dimensional resistivity cross-hole CT method is feasible for metro boulder detection.