电磁法在城市雨洪利用地下灌排系统探测中的应用

北京北海团城是著名的中国古代园林文化遗址，与四周地形比较形成一个高度为5．7m的高台，在明代建城之时，为了利用雨洪浇灌树木，城内建有地下雨洪灌排系统，为了查清该地下灌排系统的存在及其构造，采用地球物理电磁法进行了探测，探测结果显示北海团城确实存在地下渗灌和排水系统，该系统呈环状，下雨时，该系统保持尽可能多的水供灌溉用，当地下排水沟形成径流时，雨洪经各渗井流入深埋排水竖井，流出团城，作为率定试验，文中还介绍了作者研制的瞬变电磁仪探测堤防内人工隐患的详细情况。

ELECTROMAGNETIC DETECTION OF ANCIENT UNDERGROUND IRRIGATION AND DRAINAGE SYSTEM IN URBAN RAINFALL FLOOD UTILIZATION

Tuancheng Park in Beijing is a very famous ancient park culture ruin in China. It is a platform about 5 m higher than the surrounding landform. In order to irrigate trees, an underground irrigation and drainage system was built during the construction of the park in Ming Dynasty. In order to identify out the existence of the system and its structure, the geophysical electromagnetic technique is applied to detect and position the underground system. The result of detection shows that there is an underground irrigation and drainage system in Tuancheng Park, and its shape is round. In rainy days, the system keeps as much water as possible for irrigation, and the surplus water is drained out through deep drainage wells when stream forms in the underground drain. As a calibration experiment, the detection of man made hidden defects in a levee with transient electromagnetic meter developed by the authors is introduced.