瞬变电磁法对隐伏岩溶探测的影响因素研究

Research on the influencing factors of transient electromagnetic method on the detection of hidden Karst

发育于地下灰岩地区中的隐伏岩溶给隧道、桥梁以及高速公路等工程的建设与运行带来了极大的安全隐患.城市中常见的路面塌陷情况,多数也是由于岩溶发育导致.利用岩溶与其周围灰岩之间的物性差异,多种地球物理探测方法对隐伏岩溶结构进行有效探测.瞬变电磁法由于其探测效率较高、勘探成本低且对低阻异常体灵敏等特点,近年来在地下隐伏岩溶探测中发挥着重要作用.本文针对地下隐伏岩溶的主要特征,采用一维正反演模拟方法,对瞬变电磁探测隐伏岩溶的影响因素进行了系统研究.详细分析了瞬变电磁关断效应、岩溶的深度与规模、发射与接收回线尺寸及位置、覆盖层电阻率及岩溶充填情况等重要因素对瞬变电磁岩溶探测的影响.探讨总结了瞬变电磁法对隐伏岩溶地质体探测的有效性,研究结果可为实际瞬变电磁岩溶探测的工作设计与实施提供重要参考.

The hidden karst developed in the underground gray rock area has brought great safety hazards to the construction and operation of tunnels, bridges and highways. Most of the road collapses that are common in cities are caused by karst development. Using the difference in physical properties between karst and surrounding gray rock, a variety of geophysical detection methods can effectively detect hidden karst structures. The transient electromagnetic method has played an important role in the detection of underground hidden karsts in recent years due to its high detection efficiency, low exploration cost and sensitivity to conductive anomalies. Aiming at the main characteristics of underground concealed karsts, this paper adopts a one-dimensional forward and inverse simulation method to systematically study the influencing factors of transient electromagnetic detection of concealed karsts. The effects of transient electromagnetic shut-off effects, the depth and scale of karsts, the size and location of transmitter and receiver loops, the conductivity of the overburden and the filling conditions of karsts and other important factors are analyzed in detail. The discussion summarizes the effectiveness of the transient electromagnetic method in detecting hidden karst geological bodies, and the research results shed light on the design and implementation of actual transient electromagnetic karst detection.