Various geological disasters can easily occur in tunnels that pass through a limestone stratum. The fine detection of the karst system is significant for safe construction. In this paper, a progressive integrated geophysical method is proposed for fine detection of the karst area of an urban subway. The method combines ground-penetrating radar (GPR), transient electromagnetics (TEM), cross-hole electrical resistivity tomography (ERT), and 3D laser scanning to provide quantitative and integrated detection imaging in a shallow karst system. First, 3D images of reflected waves and the apparent resistivity in the study area are determined using GPR and TEM methods, and the key development of abnormal karst bodies along the mileage direction is delineated. Meanwhile, the TEM slice combination results intuitively show the low-resistance anomaly's distribution and development direction. The main water channel is inferred within the detection range. Second, cross-hole ERT exploration is performed to realize the type of judgment and accurate positioning of karst caves. Finally, 3D laser scanning is conducted to obtain the 3D spatial orientation and size of the large-scale caves identified or those that could have a large influence on metro tunnel construction. Geophysical survey results provide a reference for the design and parameter selection of the cave grouting treatment scheme. This method has been effectively applied in a shield section of the R1 line of the Jinan Metro.

中文翻译：

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地铁施工中岩溶探测的渐进精细综合地球物理方法

穿过石灰岩地层的隧道很容易发生各种地质灾害。岩溶系统的精细检测对于安全施工具有重要意义。在本文中，提出了一种渐进式综合地球物理方法，用于城市地铁岩溶区的精细检测。该方法结合了探地雷达 (GPR)、瞬态电磁学 (TEM)、跨孔电阻率层析成像 (ERT) 和 3D 激光扫描，在浅层岩溶系统中提供定量和综合探测成像。首先，利用探地雷达和透射电镜方法确定了研究区反射波3维图像和视电阻率，勾勒出沿里程方向异常岩溶体的关键发育。同时，TEM切片组合结果直观显示低阻异常' s 分布和发展方向。在检测范围内推断出主要水道。二是进行跨孔ERT勘探，实现溶洞类型判断和准确定位。最后，通过 3D 激光扫描获得已识别的大型洞穴或可能对地铁隧道建设产生较大影响的洞穴的 3D 空间方向和尺寸。物探结果可为溶洞注浆处理方案的设计和参数选择提供参考。该方法已在济南地铁R1线盾构段得到有效应用。进行跨孔ERT勘探，实现溶洞类型判断和准确定位。最后，通过 3D 激光扫描获得已识别的大型洞穴或可能对地铁隧道建设产生较大影响的洞穴的 3D 空间方向和尺寸。物探结果可为溶洞注浆处理方案的设计和参数选择提供参考。该方法已在济南地铁R1线盾构段得到有效应用。进行跨孔ERT勘探，实现溶洞类型判断和准确定位。最后，通过 3D 激光扫描获得已识别的大型洞穴或可能对地铁隧道建设产生较大影响的洞穴的 3D 空间方向和尺寸。物探结果可为溶洞注浆处理方案的设计和参数选择提供参考。该方法已在济南地铁R1线盾构段得到有效应用。