22-27 September 2019
Trade Fairs and Congress Center (FYCMA)
Europe/Madrid timezone

Monitoring technology of groundwater-air pressure (enclosed potentiometric) for karst collapse studies

23 Sep 2019, 11:45
15m
Auditorium 2 ()

Auditorium 2

Oral Topic 5 - Tools, methods and models to study groundwater Parallel

Speaker

Prof. Xiaozhen Jiang

Description

Karst collapses often occurred rapidly without prior warning. The early warning for potential karst collapses has been one of the most challenging problems around the world. In fact, many karst collapses are kind of sudden geohazards and mainly induced by abrupt changes of groundwater-air pressure within karst conduit systems. The meaning of groundwater-air pressure can be interpreted as enclosed potentiometric. Traditionally, only groundwater level monitoring with long-period sampling was applied to monitoring the karst collapses, which did not reflect the groundwater-air pressure changes within karst conduit systems. The monitoring technology of groundwater-air pressure for karst collapse was put forward from the bench-scale physical model experiments of karst collapse by the Institute of Karst Geology in 1998. In 2000, this technology started being applied to field monitoring. Over the past 20 years, the technology has been continuously improved by the application of 11 high-risk collapse-prone areas for sinkhole risk assessment, finding the triggering factors for the karst sinkholes, and controlling the groundwater drawdown during construction of underground space in these karst areas. The key elements of this technology include three parts: 1) Borehole completion specifications. The layout and depth of monitoring boreholes should intercept karst conduits. 2) Sealing measures to isolate the air-pressure inside and outside the monitoring borehole. The top of casing pipe in the monitoring borehole should be sealed to avoid the influence of atmosphere and to reflect the real conditions of groundwater-air pressure changes following the installation of the transducers. 3) Data monitoring intervals. The sampling frequency of monitoring should be 5 to 20 minutes due to effectively capture the sudden change of karst groundwater-air pressure. The pressure transducers used in this technique are retrievable and can be reused or recycled. This technology is of creative and important significance for the monitoring and early warning of karst sinkholes.

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