Detection of an ancient underground irrigation and drainage system by electromagnetic technique

摘要

An ancient project of rainfall flood utilization in city is introduced here. Tuancheng Park in Beijing is a very famous ancient park culture ruins in China. The form of the park is like a platform of about five meter higher than surround land. In this type of adverse circumstances, some 800 years old trees have been still growing very well because there is an underground irrigation and drainage system, which was built during the park construction in Ming Dynasty. When raining, rain water is used to irrigate the trees as much as possible; when heavy raining, the system keeps enough water for irrigation in dry days, and surplus water is discharged out of the park to prevent tree roots from long time immersion. In order to delineate the system, the authors employed geophysical electromagnetic technique as nondestructive testing (NDT) for detecting and locating the underground structure of the system. The detection result shows that there is an underground irrigation and drainage system in Tuancheng Park, indeed; the shape of the system is like ellipsoid; and surplus water was discharged through deep drainage well when runoff forms in the subdrain.