Singapore's two largest universities have completed exploratory studies to see if they can tap their campuses' underground space for classrooms, libraries, sports halls and other facilities.
The National University of Singapore's two-month study was completed late last year while a research group at Nanyang Technological University (NTU) will finalise its report by next month.
NUS' vice-president of campus infrastructure Yong Kwet Yew said delving underground would expand use of the Kent Ridge campus' land while conserving existing green and open spaces on the surface.
"In the exploratory study, some possible uses identified included sports facilities, classrooms, libraries, auditoriums, and even research laboratories, data centres and parking structures," he told The Sunday Times.
However further studies are needed, such as how to make the underground spaces more comfortable for people, for example through the use of natural lighting.
He added that the university is also exploring research areas related to the use and development of underground space, but did not elaborate further.
Meanwhile at NTU, students could eventually swim in a subterranean pool or borrow books from an underground library.
Its Nanyang Centre for Underground Space (NCUS) led a year-long study with an international team of researchers to outline how the university can expand underground.
The study was sponsored by NTU's Sustainable Earth Office and the researchers said it could complement the university's 15-year masterplan to develop the campus, which was unveiled in 2011.
Among other things, the NCUS report - which comes out next month - will provide preliminary designs for a four-storey underground learning complex and a three-level sports hall below the Jurong campus' surface.
The NCUS' interim director Zhao Zhiye said: "NTU may not build these underground facilities in the near term, but this concept study will be a good start for planning purposes."
For example, if the university wants to expand below the surface, it will need to set aside space above-ground for access shafts.
The report is based on available data about the NTU grounds' geology and topography, and sets out concept plans for caverns, tunnels and basements and how these could be linked to the surface.
The underground learning centre, for example, consists of 220,000 sq m spread over four levels, including space for libraries, function rooms, and a main concourse.
The three-storey sports hall would be located under the existing sports centre on campus, and feature a swimming pool and courts for indoor games such as badminton and basketball.
The researchers estimated the amount of rock that would need to be excavated for these two facilities, but not their price tags as these could change depending on the subsurface geology.
The report's principal investigator Zhao Jian, a rock mechanics and tunnelling professor at the Ecole Polytechnique Fédérale de Lausanne in Switzerland, added that the report will include information from previous studies on underground facilities' safety and sustainability.
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