Incidence of sinkholes is on the rise mainly in large cities with dense population in Korea. Sinkholes sharply increased from a dozen in 2012 to 60 in 2014 and 240 in 2016. One of major causes of sinkhole is subsidence of land due to lowered ground water level. Underground structures of buildings, subways or obsolete drainage ways are main routes of groundwater discharge, which causes sinkholes while damaging lifespan and safety of underground structures such as basement parking lots at apartment houses.
Under the situation, the Ministry of Land, Infrastructure and Transport (MOLIT) announced at the end of last year a guideline for preventing leakage from underground structures and their waterproof design. This guideline was drawn up based on results of a study on developing technologies for preventing, diagnosing and restoring performance of underground structures of apartment houses. The guideline is designed to help building designers, constructors and supervisors build comfortable residential environment without water leak.
The guideline was prepared by a team led by Prof. Oh Sang-geun, Director of Waterproof Technology Research Center at Seoul National University of Science and Technology (SeoulTech), who is widely recognized as a world-level authority on waterproof technology as he has been devoting to development of waterproof engineering for about 30 years. Prof. Oh Sang-geun took initiative in registering the ‘new technology for leaks restoration’ as an international standard, and worked out in 2010 the ‘general guideline for repairing water leakage and cracks in concrete structure’, the first of its kind in Asia, and enrolled it as the ISO TR16475 in 2011. This helped Korean companies increase export of waterproof technologies and products to world markets, including the United States, Japan and the Middle East.
In recognition of these achievements, Prof. Oh was honored with several medals and awards in Korea. Currently, he is the president of Korea Institute of Building Construction and the Convener of the SC7/WG3 in the ISO TC71.
“While construction of apartment houses is sharply increasing, most of their underground structures are involved with varied problems caused by lowered ground water levels, such as subsidence of ground, infiltration of radon, which is a radioactive substance contained in underground minerals, generation of microorganisms and bad smell due to water leak, and corrosion of steel frames in underground structures. Yet, either the government, construction companies or residents recognize seriousness of this situation. And now is the time to work out a standard waterproof design for preventing underground leakage in apartment houses to reduce enormous economic and social costs,” said Prof. Oh Sang-geun.
In the guideline, Prof. Oh stresses the ‘outside waterproofing measure’ that can basically shut off inflow of underground water instead of conventional ‘inside waterproofing measure’. The outside waterproofing measure is a method of installing waterproofing layer on external walls of concrete structures to fundamentally block inflow of water. The outside waterproofing method is much more effective than the inside waterproofing method in reliability of waterproof, resistance to ground water pressure, protection of structures and dampproof.
In continuation to creation of the guideline, Prof. Oh is taking part in the ‘project of developing optimization technology for preventing leakage and restoring underground structures in apartment houses’. He also strives to educate young specialists in waterproofing technology.
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