Topic		14:50 – 15:15
Detection of Underground Voids in the Vicinity of Pipelines
Speaker	Prof CHAN Lung Sang
	The University of Hong Kong
Session Summary
Geophysical methods that may plausibly be used for detecting subsurface voids include ground penetrating radar (GPR), seismic reflectometry, electromagnetic survey, electrical resistivity imaging and acoustic noise detection systems. Several trials recently conducted in Hong Kong using electromagnetic and electrical methods reveal varying extent of success in identifying anomalous ground condition and underground pipes. In most cases, the methods could not unambiguously identify the presence of voids. Even when useful results were obtained, the methods should be regarded as indicative measures and not for definitive determination. The use of geophysical methods in void detection at traffic speed in the vicinity of underground pipe poses an even greater challenge. Other techniques such as GPR, smart ball and noise detector may show relatively greater success in local and overseas case studies. However, the effectiveness of the geophysical methods is often site-specific, and subject to interferences by nearby objects. In this talk, the speaker with discuss findings from several case studies in Hong Kong on the use of non-invasive geophysical methods in detection of underground voids.
Presentation Materials