How are underground structures constructed?

Some of you have been asking me how underground structures are built, so here’s a simple summary.

There are two methods of excavation, drill-and-blast and using the tunnel boring machine. Drill-and-blast is a cyclical procedure, where the rocks are first drilled, blasted with explosives, ventilation is created, then the overhanging rock is supported by rock bolts or concrete, and the whole process repeats itself (Zhao & Tan, 2012). 

Drill-and-blast process. Picture taken from www.mtr-shatincentrallink.hk/en/construction/construction-methods

Using the tunnel boring machine on the other hand is a continuous procedure (Zhao & Tan, 2012). The tunnel boring machine looks like a ferocious, teeth-baring earthworm enlarged up to a 100 times. I know, earthworms do not have teeth, but just imagine a set of nasty spiralling teeth in them, and you have a tunnel boring machine! The Cutterhead, which is the front part of the elongated machine, contains roller cutters. Pushing the machine in and rotating the Cutterhead helps to crack hard rocks (Zhao & Tan, 2012).

Tunnel boring machine. Picture taken from www.dlr.de

Both methods have their strengths and weaknesses and they are used for different rock types and ground conditions. For example, the tunnel boring machine can work on soft to the very hard rocks, but it fails in drilling rocks of differential geology, where strong rocks are mixed with weak rocks. Drill-and-blast is suitable for differential geology but it cannot cope with groundwater seepage (Zhao & Tan, 2012).

Therefore, before tunnelling works can take place, engineers have to investigate the underground properties, like rock types and the level of groundwater infiltration to choose the appropriate excavating process.

Literature cited:

Zhao, J. & Tan, S. B. (2012). Underground space development in Singapore rocks. PTRC and NCUS Workshop on Underground Space and Rock Cavern Development in Singapore, NTU. 17 January 2012.

Is underground space the answer to our problems? (journal review)

In the journal article, “Sustainable Development and the Use of Underground Space”, underground tunnels and buildings are hailed to be the solution to sustainable development. Roberts’ (1996) idea of sustainable development was one that limits imports, has efficient and effective infrastructure systems, maximises the use of urban and rural lands, and produces cost-effective exports with the least waste. Municipal waste should also be re-used as inputs for agriculture.

By limiting imports, Roberts is suggesting that agriculture has to be expanded to meet the needs of a growing population. He argues that rural areas should be kept as agricultural lands, which means that development and construction has to be focused in already urbanised areas. He envisions that “future megacities will be concentrated, attractive and healthy places to live, surrounded by rural areas”.

However, such a plan is difficult to accomplish for countries with small land areas (such as Singapore). Farming in these small countries can hardly meet the demands of the population. Expanding farming would mean that urbanized lands have to be retreated for ‘rural’ lands. Although high intensity farming can help increase output with the restricted space, it is usually too costly for long-term dependency. Of course, such a move would be going against the nature of economics because it would be forcing countries with no comparative advantage in agriculture to grow their own food. On another note, it is possible that instead of having agriculture, the intended lands for farming can undergo reforestation which can reduce the overall carbon footprint of the country.

According to Roberts, using underground space has many benefits to the environment in terms of resource recycling, reduction of vehicle carbon emission, recovery of farm lands, and energy savings.

The first benefit he talked about is resource recycling. In order to reduce waste, the waste products of one industry can be the raw materials of another. Industrial parks can be connected via underground tunnels, for the transportation of waste products to the industry that can use them, for the construction of combined waste treatment plants (which can be more efficient as the scale is bigger), and the exchange of cooling/heating waste water (water used for cooling purposes that is heated up and no longer useful can be passed on to industries that require heated water). Of course, all these would need a low-energy delivery system located underground. Such an idea is feasible and has great potential to reduce wastage and even lower energy consumption, but it is only practical in counties with highly diversified industries. Otherwise, it is very unlikely for one industry to find the waste products of another as potential raw materials.

Photo from Jamiecphotos.com

The second benefit of using underground space would be the reduction of vehicle emissions. By developing an efficient and reliable underground mass public transportation system, it would encourage commuters to switch to the cheaper and faster alternative which is underground. This would decrease the number of motor vehicles on the road. Less petroleum would be used and less carbon dioxide and acidic gases would be emitted. Since transport, in particular motor vehicles, is a significant contributor to anthropogenic carbon emissions in Asia and most likely the whole world, a reduction in vehicle volume would definitely alleviate the pressures of global warming (Ohara et al., 2007). Such a massive transportation system would be best situated underground because the ground can snuff out the high decibels generated by the rapidly moving trains and also the system would be protected from destructive natural forces like hurricanes and even earthquakes. 

Lastly, Roberts highlighted the most important function of underground structures which is energy savings. Underground structures can reduce the amount of energy required for the running of factories, transportation, offices and homes. It was indicated in the article that studies have shown that decreasing energy consumption by as much as 50% would have no reduction in standard of living. This proves that lowering our energy needs would have almost no trade-offs to living quality. He also wrote that “improvements in energy efficiency will be more economical than developing new supplies of energy”.  I believe that this is the most optimum measure in the present moment. While alternative sources of energy are being developed, we should cut down on our use of energy as much as possible until a viable source is found. Research on renewable energy is imperative and the government should pump funds into research. But at the same time, we need to actively reduce our exorbitant energy usage to minimise the damage done to our environment.

In conclusion, the use of underground space is a potential solution to a sustainable future, but it is not the best or only solution. This is because the effectiveness of underground structures may not apply to every country and construction costs are high. It is recommended that larger developed countries explore the use of underground space in those aspects suggested by Roberts and assess the advantages. Developing countries should also start taking an interest in underground structures and draft out plans of their future land use. They should also conduct exploratory studies to determine the feasibility of underground projects. Singapore is still relatively new to underground structures and more improvements can be made to expand underground transportation systems and make it more efficient.

Article reviewed:

Roberts, D. V. (1996) Sustainable Development and the Use of Underground Space. Tunnelling and Underground Space Technology. 11 (4). p. 383-390.

Literature cited:

Ohara, T. A. et al. (2007). An Asian emission inventory of anthropogenic emission sources for the period 1980–2020. Atmospheric Chemistry and Physics. 7(16). p. 4419-4444.

Surprise interview segment

Dr Jose C. E. Mendoza on underground living, the environment and outer space (?)

What is your opinion on living underground?

You know, I’m a biologist, so I love the outdoors, I love to be in open spaces. Or else I would feel quite claustrophobic. That being said, if it is a necessity, I don’t mind using the underground for things like storage, but not as living space. I have faith in the ingenuity of people, they can make conditions underground as close to the surface as possible.

What kind of structures do you think should be placed underground?

[He chose everything except residence of course!] Offices, schools, retail, sports facilities, research labs (definitely!), and transport (We’re already doing that right?). But I think what’s most important is that we make good use of the space and do not affect the aesthetics of the land. Actually, I would prefer to live under water, I mean we can get a sense of space there. Or maybe even outer space! We always have those fantasies to colonize the moon. Underground living is something really new to me.

Given that Singapore is facing land constraints and a likely increase in population, how do you think we should plan our land use? (E.g. building upwards, building downwards, reclaim land, clear land)

I think that going upwards or downwards doesn’t make any difference, because when you are building upwards you are also preparing for building downwards. We should exhaust all possible lands first. You see, Singapore is both a city and a state. I would say Singapore is more of a city than a state.

So you’re definitely against the clearing of land?

We should intensify the use of land that are already quite built up rather than use those small patches of forests. Keep these patches, increase the connectivity between Bukit Timah Reserve and the Central Catchment. And if we want to build underground we have to do site explorations to see if Singapore is suitable for underground constructions. It must also be cost-effective.

Do you think that underground buildings are better or worse for the environment?

I’m just thinking what do we do with the rocks that are being excavated?

We can use the excavated rocks for reclaiming land.

Aha! So that is the problem. [Gives a wide grin]

Oh, so you think land reclamation is not good?

Yea, reclaiming land is not good. Because where are we going to reclaim our land from? Most likely mangroves at the coastline. It’s going to affect mangrove areas which have a lot of biodiversity. In Singapore, there is concern to preserve biodiversity. We still don’t know what biodiversity we have in the coastal areas. You don’t know until you do a proper study… This is a very boring response hor? [Not at all, Dr Mendoza :D] When you build something underground you will disturb what is on the surface. Just like the plan to build the CIL [Cross Island Line] under the CRR [Central Catchment Reserve], when you drill underground, it could lead to a crack in the rocks, and then what? [Prompts me for the answer. Err…animals in the reserve would be affected?]

Actually, we can use the excavated rocks for paving roads too.

Paving roads ah… Do we need so many roads?

What we should be thinking is what exactly is fuelling this demand for space? A lot has got to do with economic growth. We can just live with less, lower our ecological footprint, then we don’t need all that space. We cannot always create solutions to our problems, we have to change our mindsets. If there is an option to live with less, I’d go for that option.

What would you like to know about underground structures?

Erm, how they’re built, what are the applications in Singapore, what are the impacts on the environment, and what kind of psychological problems would it bring. [I guess that’s more work for me!]

Quote of the day from Dr Mendoza: “Do we need all that space?”

P.S. I would like to thank Dr Mendoza for his patience in sharing his thoughts with me, even though I just sprung out of nowhere without giving him time to prepare. 

[Date interviewed: 13 October 2014]

Underground Structures in Singapore Part 2: The industries

Jurong Rock Caverns

Land in Singapore is so precious that simply using it to store commodities is such a waste. The Jurong Rock Cavern is a 130-metre-deep cave under Jurong Island that stores oil like naphtha and condensate (JTC, 2014). It is meant to free up surface space so that space above the ground can serve other important uses instead of just storing hydrocarbons.

Photo from JTC, 2014

Interesting facts about the Jurong Rock Caverns (Lim, 2014):

1.       This project took 6 years of planning and 8 years of construction.

2.       Why so long? Because the cavern is hollowed out using explosives and it takes 1.5 to 2 years for each cavern to be excavated.

3.       The caverns made available 60 ha of land on the surface.

4.       The caverns are the deepest known public construction in Singapore, deeper than the deep tunnel sewerage system (remember this from our NEWater field trip?)

5.       The 3.5 million m³ of rock excavated will be utilised for land reclamation and laying roads.

6.       During the caverns’ opening ceremony, Prime Minister Lee Hsien Loong announced that this project exemplifies Singapore's determination to develop a petrochemical industry, despite our limited land area and the likely effect of the coming UN Framework Convention on Climate Change treaty on carbon emissions.

Underground Science City

Photo from Straits Times

When we think about an underground research lab, we would probably think of an evil villain’s secret lab where all the genetic experiments, flasks full of weird chemicals or robotic assistants are hidden. Well, there are plans to build an underground research lab in Singapore, not for mad scientists of course, but for research and development. JTC is considering the proposal of an underground Science City to be located underneath Kent Ridge Park (not too far from NUS!) which could house “4200 scientists, researchers and professionals” (Feng, 2012). The Science City would consist of 40 connecting rock caverns and up to four levels worth of commercial space (Feng, 2012). According to the Straits Times report (2012), building a science city beneath the ground can make use of the ground’s natural isolation against noise and vibration and can easily contain the fall-out of hazardous substances.

If underground structures are so great, why hasn’t Singapore built more of them? The answer lies in the cost of constructing underground buildings. The differential rock geology of Singapore’s ground makes excavation more expensive (Chin, 2013). An example would be the harder granite and norite rocks found in Bukit Timah and Bukit Gombak respectively (Sharma et al., 1999). On the other hand, the sedimentary rocks in Jurong are quite weathered, making them easier to excavate. According to the Straits Times report by Chin (2013), the cost of building one storey below ground is the same as building three storeys on the surface. This can be very expensive judging by the number of underground structures we have to build to compensate for those above ground. Hence, unless Singapore has exhausted all means of cost-effective land use, underground structures are not likely to dominate the country in the near future.

Stay tuned to the next post for something really interesting and unexpected (I hope)!

Literature cited:

Chin, D. (2013) Singapore’s (costly) underground ambitions. The Straits Times. 10 September 2013.

Feng, Z. K. (2012) JTC looking at plan for underground science city. The Straits Times. 14 November 2012.

JTC Corporation. (2014) Jurong Rock Caverns. [Online] Available from http://www.jtc.gov.sg/RealEstateSolutions/Pages/Jurong-Rock-Caverns.aspx. [Accessed: 12 October 2014]

Lim, L. (2014) Singapore opens S$950m underground rock cavern at Jurong. Channel News Asia. [Online] 2 September 2014. Available from: http://www.channelnewsasia.com/news/singapore/singapore-opens-s-950m/1341836.html. [Accessed 11 October 2014]

Sharma, J. S., Chu, J. & Zhao, J. (1999) Geological and Geotechnical features of Singapore: An Overview. Tunnelling and Underground Space Technology. 14(4). p.419-431

Underground structures in Singapore Part 1: The underground campus

NUS is no small campus. It has so many faculties and facilities- Science, Engineering, libraries, the SRC... Utown was even added recently to provide the booming student population with more lecture theatres and recreational places. Yet we somehow feel that these are not enough. We need more classrooms, more lecture theatres, more sports amenities, more laboratories. But we are already squeezing the very last land space we have, any more and the school would lose its beauty and liveability. At this point you might have guessed. Yes, go underground!

Both NUS and NTU have just finished their exploratory research on the feasibility of underground development. NUS vice-president of campus infrastructure, Yong Kwet Yew mentioned in an interview by the Straits Times that going below ground can allow the space of Kent Ridge campus to be maximised while keeping the present green and open spaces aboveground. He raised the possibilities of “sports facilities, classrooms, libraries, auditoriums and even research laboratories, data centres and parking structures”. However, there was no real proposal for the construction of these buildings and Dr Yong called for more studies on ways to make underground areas more comfortable such as using natural illumination.

As for NTU, there are plans to build a four-storey underground learning centre and a three floors worth of sports hall below ground. The lucky NTU students would one day get to swim in an underground swimming pool! (Feng, 2013)

What about SMU you may ask? SMU already has an underground link-way that connects the five major buildings and the Bras Basah MRT station (The Business Times, 2013).

Is the idea of expanding underground good news for you? If we cache some of our buildings underground the surface would look less ‘cluttered’. We can afford to have more trees and even wildlife. It would be a wise move to shift air-conditioned buildings below the surface since they would then require less energy for cooling. However, for large scale buildings like libraries and auditoriums, safety measures have to be thoroughly studied and communicated to students. Hence, for a start, laboratories should still remain on the surface due to the higher risk of a fire hazard where the effects would be more rampant in underground enclosed spaces.

When we talk about studying, we probably would not think it a big deal to have it underground, but when it comes to actually living underground permanently that is when we would start hesitating.

Literature cited: 

Feng, Z. K. (2013) NUS, NTU complete studies on underground campus. The Sunday Times, Home. p.18. [Online] 14 July 2013. Available from http://newshub.nus.edu.sg/news/1307/PDF/CAMPUS-st-14jul-p18.pdf. [Accessed 3 October 2014]

The Business Times. (2013) NUS, NTU look into underground expansion. p.8. [Online] 24 September 2013. Available from http://www.smu.edu.sg/sites/default/files/smu/news_room/smu_in_the_news/2013/sources/sept24/bt_20130924_1.pdf. [Accessed 3 October 2014]

The 2 challenges

The two key challenges of building underground residences are lighting and ventilation. Sure, we can install numerous lights and use powerful air-conditioning like what we have in our underground MRT stations and shopping centres. However, that would negate the savings in electricity that underground buildings are said to bring (remember the temperature stability and lower energy requirements to heat/cool them?). I’m sure our immediate response in a basement carpark is to get out of that place as soon as we can, find the nearest door to air-con! At three storeys below ground, the air is just humid, stagnant and warm.  If we are to switch on all the lights and air-conditioning units at full power every single day, 24/7, think about the crazy energy usage! We might as well be better off squeezing on the surface. Besides, living in a windowless environment with ‘white light’ all the time isn’t healthy for us in the long run. Just imagine living in your office or tutorial rooms, that kind of man-made feeling might just drive us to depression. That’s why we need an energy-efficient ventilation system and natural light.

One energy-saving ventilation system currently used by the Ewha Campus Centre building in Seoul, South Korea is the thermal ventilation system. In such a system, there will be an underground labyrinth where air from outside can be forced in and heat is lost to the ground (Song et al., 2014). The cool air can then be enjoyed by occupants of the building. This system has been proven to be effective as the yearly energy demand for conditioning outdoor air decreased by 31.3% (Song et al, 2014). Engineers can also consider pumping air underground to ensure good ventilation. By allowing air to enter low enough, it can be sufficiently cooled by the earth and sink below to reach the people. Meanwhile, warm air generated by the population can rise up via another set of shafts. Hopefully more innovative technologies will come about as more and more governments consider underground structures.  

Natural light from the sun has many benefits: it increases visual performance, hence heightening alertness and concentration, it soothes the mind and it induces the skin to produce vitamin D which is important for calcium and phosphorus absorption from food (Hughes, 1987). As such, if we are able to simulate natural light, replacing artificial fluorescent lamps with lighting that emits rays of similar wavelengths as that of the sun, then we can achieve maximum bodily functions and comfort. It is not too difficult to simulate natural light as we only need to select the correct wavelengths. Also, the “remote skylight” technology proposed by Ramey in the Lowline can be combined with natural simulation to create a pleasantly lighted environment for the underground dwellers. 

Picture taken from Lowline (2014)

Other forms of renewable energy sources such as solar or even kinetic can be considered to power the lights in the underground building as well.

If you ever miss the natural breeze and sunlight, you can always take the elevator (or stairs, if you’re not that deep into the ground) to the surface where nature would be more beautiful since there would be less tall buildings fighting for space.

Literature cited:

Hughes, P. C. (1987) The use of simulated natural light in the design of earth-sheltered environment. Tunnelling and underground space technology. 2 (1). p.75-81.

Song, S. Y., Song, J. H. & Lim, J. H. (2014) Effectiveness of a thermal labyrinth ventilation system using geothermal energy: A case study of an educational facility in South Korea. Energy for Sustainable Development. 23. p.150-164.

There's a garden under my home!

Remember the no-sunlight-and-all-concrete-walls depressing scenes? We talked about how unliveable that kind of environment would be like. Well, it is not impossible to have greenery in the depths of the crust. In fact, projects are underway for the world’s first ever underground park, located in New York! 

Picture from www.kickstarter.com

The Lowline is a proposal for a community park underneath the bustling city of New York, in a long abandoned trolley terminal (The name is inspired by the successful highline park in New York). The team behind the project even overcame the challenge of providing sunlight to the plants using nothing but a few reflective dishes. The “remote skylight” as it is called is the brainchild of James Ramey, the co-founder and creator of Lowline. The technology harvests natural sunlight from aboveground and concentrate the rays onto a focal point after which the light energy is transferred underground via fiberoptic tubes and spread across the facility by interconnecting reflective domes on the ceiling (Lowline, 2014). With that, plants can photosynthesize in an otherwise dark room. By using natural sunlight, it also means that electricity is not needed to power bulbs in the day time.

You can find out more about the Lowline project by watching their promotional video:

 And, of course, they succeeded in building their prototype! They have proven that it is very possible to have a park full of healthy trees and shrubs below the ground. Residents in that area can relax at the park even when it is raining or freezing cold in winter.

According to Asimov (1989), one advantage of living underground is to make space aboveground, so that forests need not be cleared for more urbanisation. People can enjoy nature both underground and above, and the ecosystems on the surface would be in better shape.

Would you like an underground park in Singapore too? With greater wildlife and forests conservation by not touching present forests, it looks like living underground can truly make us a garden city!  

Literature cited:

The Lowline. (2014) Project. [Online] Available from: http://www.thelowline.org/about/project/. [Accessed: 20 September 2012].

Asimov, I. (1989) The advantages of underground living. Los Angeles Times, ProQuest Historical Newspapers. [Online] 2^nd June. P D2.

(I'll be using the Harvard referencing style from here on)

In 'depth': living underground

Imagine opening your eyes to the smell of gravel and sand. You know it’s the morning but your room is in complete darkness. Your hand feels around for the button conveniently located at the side of your bed. The light flicks on. You wince at the sudden assault of light rays from the bulb. Your head instinctively turns to the window where the trees would be swaying in the morning breeze, cars would be zooming by and housewives would be scuttling to the market, giving a vivacious review of last night’s drama. But then to your horror, you are reminded of the fact that you don’t even have a window.

This is probably a scenario which we would associate with living underground. After all, we are moving below the surface, covered by layers of silt and soil, far away from surface life. We think about the animals adapted to living underground such as the naked mole rat. Aren’t they a bunch of odd-looking creatures? Would we turn out like them if we live underground for too long? Apart from the fear of storing explosive or toxic chemicals in underground caverns, people are distressed over the potential health complications of long-term residence underground (Evans et al., 2009). Claustrophobia may be possible, since there is no stimulus from the outside environment. Living below ground also means that we won’t get our daily dose of sunlight and the calcium retaining vitamin D that comes with it. According to Michael J. Breus, diplomate of the American Board of Sleep Medicine, natural light helps reset our internal biological clock every day which in turn affects our mood, metabolism, body temperature and immune system. We need to see and feel sunlight to be able to have some form of a sleep pattern. Ventilation is also a concern as we need to make our underground homes feel less like a stale prison cell. What about green spaces? We certainly cannot live with just looking at concrete every day. Thankfully, there are solutions to all these worries with technological advancements which could minimise the difference between underground residences and those on the surface.

Sadly, there are barely any studies done on the psychological impacts of living underground. But with today’s people already working and studying in windowless environments, or have their blinds down and windows blackened out, they probably would have no problem adjusting to life underground. A study on the attitudes and satisfactions of earth-sheltered housing to a group of people in Minneapolis-St Paul, Minnesota found that the earth-sheltered residence was generally desirable. Their attitudes towards underground living improved after they had lived in the houses (Bartz, 1986). However, 50% of townhouse residents in the survey felt like escaping from their house, and 21% of the single-family group had the same feeling. Their reasons include not wanting to finish the house and household chores (I’d run out of my house anytime if I have household chores to do).

Most important is the impact on the environment when we excavate the ground. Evans et al. (2009) pointed out that if not done properly, underground development could result in damage to the constructions above ground, exposing overhanging pieces of land, stopping groundwater flows, causing wells to dry up or allowing seepage of pollutants that lower groundwater quality. By moving underground, we may also be competing with the animals that have long exploited the underground space as their habitat.

With the tightening squeeze we are facing on our lands, living underground may not even be up to our choice. It’s either that or an underwater city, right? And let’s not go into the sensibility and practicality of that.

Literature cited:

Bartz, J., 1986. Post-Occupancy Evaluation of Residents of Single- and Multi-Family Earth Sheltered Housing. Tunnelling and Underground Space Technology, 1(1): 71-88

Breus, M. J., 2010. The effect of circadian rhythms on the sleep cycle. Sleep Newzzz, 11 November 2010. URL: http://www.psychologytoday.com/blog/sleepnewzzz/201011/underground-and-out-sight. Last accessed 20 September 2014.

Evans, D., M. Stephenson, & R. Shaw, 2009. The present and future use of ‘land’ below ground. Land Use Policy, 26: 302-316

Build it like the termites

Termites are often called the architects of the insect world. Standing at a whooping height of 7.5m (Anitei, 2007), termite mounds are definitely much more than your average anthill. Who says we can’t make a mountain out of a molehill? What lies inside the mound is a bustling city of tunnels and shafts where the termites store everything from their larvae young to their agriculture (not just food, but agriculture!). The picture below shows the structure inside a termite mound.

(Picture from Nature, n.d.)

A single vent comes down from above the mound and is connected to various tunnels that air from the whole nest can flow into (Nature, n.d.). The warmer air from the nest rises up to be expelled out of the mound while cooler air sinks. This ensures that the air circulating in the nest is maintained at a tolerable temperature. The termite city is actually located underground (number 3 as shown in the picture). There, you can see large networks of tunnels and little ‘rooms’ partitioned by thin walls. These small critters even have a fungal garden where they grow fungus that they consume. The fungus requires a steady temperature to thrive, hence it is crucial that the nest has a stable temperature. How then do the termites enter and leave the nest? There are entrances at the base of the mound (labeled number 4 in the picture). The last part of the mound is the cellar, the bottom-most structure in the mound. The top of the cellar contains a layer of thin plates that absorb moisture from the nest above. Evaporation of this moisture helps to reduce the temperature of the whole nest.

Ingenious, isn’t it?

Perhaps we can learn something from the design of the termite’s mound to create an underground city for ourselves!


Literature Cited:
Anitei, S., 2007. The Largest Natural Buildings. Softpedia, 20 June 2007. URL: http://m.softpedia.com/the-largest-architectonic-buildings-in-nature-57816.html. Last accessed on 13 Sep 2014.
Nature, n.d. The Incredible Termite Mound. Nature, The Animal House. URL: http://www.pbs.org/wnet/nature/episodes/the-animal-house/the-incredible-termite-mound/7222/. Last accessed on 6 Sep 2014.

Green Engineering! (journal review)

Benardos, Athanasiadis and Katsoulakous (2013) discussed the benefits of underground buildings as a modern residence with green engineering. An overview of the benefits of underground constructions were given, such as freeing up surface land and having low visual impact on the landscape The benefits focused on energy savings and they are presented in two ways, namely through a comparison between an underground dwelling and an equivalent surface building and through explaining the Science behind earth insulation properties. Other aspects of comparison included cost of construction, materials used and aesthetics. The journal cited previous studies that all consented with the trend of decreasing heat transfer with increasing depth. It is clear that thermal lagging is more effective with thicker earth cover. The journal then describes the geographic conditions of the experimental site as well as the designs of the underground building. It is important to note that careful details were given on how natural illumination and ventilation were achieved. Data on the heating and cooling demands of the two types of buildings were recorded on a monthly basis. The journal can be summed up to comprise of four key sections: the comparison assessment, living environment, energy usage and cost.


The comparison assessment was conducted at Kea Island, a popular tourist destination. The island already boasts some semi-underground houses, so an underground building would be no shock to the locals. The area receives plenty of sunlight, with warm temperatures, little rainfall and high humidity. The conditions are mostly similar to that of Singapore, which allows for extrapolation of the results. The comparison assessment is a fair one, as the characteristics of the two buildings are kept mostly the same. The thermal insulation used for the aboveground building was much better than stated in relative legal standards. Bernardos et al. (2013) noted some differences in variables, including excavation, building structure and material use, waterproofing and thermal insulation (waterproofing is needed for underground building, but thermal insulation is only needed for the surface building). Underground buildings require ventilation systems and light chimneys but surface buildings need more windows and doors. These were all calculated towards the cost of construction. However, it would be preferable to compare with different depths of buildings and across a wider range of comparison factors like energy consumption, living conditions, air quality and accessibility, since Singapore would likely need to explore the pros and cons of digging deeper. The study in this journal had some comparison of living environment, energy use and cost between the two types of houses. Living environment is the main consideration for any residence, much more since it is below the surface, a very unfamiliar experience to many.

(The interior of the earth-sheltered building used in the study)

Bernardos et al. (2013) acknowledged the problem of claustrophobia from living underground. It can be resolved by having a direct view of the outdoor landscape and a minimum height of at least 2.8m in the building. However, an outdoor view would only be possible if the underground building had some parts exposed. This would pose a difficulty for moving deeper underground and adding many levels. It would not be feasible and practical in Singapore and defeats the primary purpose of mitigating land constraints.


It is argued that underground buildings use up less energy in heating and cooling as compared to surface buildings. The total reduction in energy demand for cooling was greater than that for heating. The EN 13790 methodology was used to estimate energy demands and it was recognized that this method is not able to accurately calculate heat transfer due to heat capacity of the building shell of the aboveground building. This means that the energy demand of the underground house would be theoretically even lower than what was calculated (since the underground building does not have a building shell). Two solutions were even provided for covering heating and cooling loads (oil fired central heating system and central heat pumps). It can therefore be concluded that underground living reduces energy consumption and saves electrical costs. This is useful for considering underground residences in Singapore where air-conditioning takes up the lion’s share of electricity consumption (Energy Market Authority, 2001).

(The total energy demand of the underground and aboveground buildings over the months. Green represents the underground building while orange represents the aboveground building)

Construction costs were shown to favour the surface building. This is expected due to the extra cost for excavation. Bernardos et al. (2013) argued that the total cost for the underground building would be lower than the aboveground in the long run due to less maintenance cost. However, they failed to provide evidence for this claim. Underground structures might need some maintenance and regular quality checks and it is early to state that they would be cheaper than that of surface buildings.


In conclusion, the comparison assessment present in this journal is useful in proving the massive savings in energy from cooling needs. It also shows the possibility of building a livable underground home without negating aesthetics and comfort. However, little was mentioned about the disadvantages of underground buildings, which would better help in assessing the viability of underground buildings in Singapore.




Article reviewed:
Benardos, A., I. Athanasiadis & N. Katsoulakous, 2013. Modern Earth Sheltered Constructions: A Paradigm of Green Engineering. Tunneling and Underground Space Technology, 41: 46-52.

Introducing Montreal’s RÉSO!

Anyone who has been to Montreal would know that winter there is bitter and long. The cold latches on to you once you enter the open space and it can be a terrible thing for the Canadians who still have to go to work and meet up with people. Wouldn’t it nice to hibernate like bears in well-insulated burrows underground? Well, Montreal actually has a second ‘world’ located underneath their buildings and roads. An extensive underground city, RÉSO, is made up of 32 km of tunnels, covering about 12 km² in downtown Montreal. It links together more than 30 office towers (Barker, 1986), hotels, commercial shops, cinemas, universities and train stations.

It is a brilliant idea, an architectural masterpiece that Singapore can take insights from. The underground city in Montreal started out as a metro system, much like the MRT system we already have. Then they added offices, recreational facilities and shopping malls, all easily accessed with pedestrian tunnels.

Barker (1986) encouraged the idea of underground cities by stating the many benefits they bring, including “the increase in property values and land utilization, separation of pedestrian and automobile traffic, reduction of surface congestion and improved atmosphere for pedestrians”. All these are especially applicable to Singapore. By keeping pedestrians below ground and limiting pedestrian-vehicle contact, the occurrences of accidents would be reduced. There would be significant economic advantages with less traffic congestion and more efficient transport network that connects employees to their offices directly without the need for resurfacing. Also, the fear of haze would no longer be an issue if Singaporeans can hide underground.

Of course, there are many concerns with regards to digging underground and moving all our homes and offices down. Research is still in the pipeline and much investigation needs to be done to assess if Singapore is suitable to build an underground city.

According to Barker (1986), “each urban area has its own circumstances that can influence the application of the Toronto idea:

• Urban density
• Local geology
• Building configuration
• Development policies
• Environment standards”

As of now, it remains hopeful that underground living can alleviate our land woes and even provide a better living environment for us.

References and Literature Cited:

Barker, M. B., 1986. Toronto’s Underground Pedestrian System. Tunnelling and Underground Space Technology, 1 (2): pp 145-151

Khaw, B.W., 2013, Exploring Exciting Possibilities Underground. 3 September 2013. URL: http://mndsingapore.wordpress.com/. (accessed 15 August 2014)

High housing prices? Move underground!

With a population of 5.4 million and land area of only 7.16 sq km, Singapore is already facing a tight squeeze. One can easily relate to the exasperation felt by your everyday Singaporean, whether it is crowed public transport, congested roads, or housing prices as high as the buildings go. 

To fight the problem of limited land, our government has chosen to build higher and higher, smaller and smaller, coming up with shoebox apartments that are like sardine cans for people. 

Even that is not enough. As we anticipate a 1.5 million population increase by 2030, we would need more land space. Years of development has culminated in a city dominated by skyscrapers and reclaimed land. Going higher has its limitations. There are height restrictions around air bases and we simply cannot keep building higher indefinitely. Already reclaimed land contributes to one-fifth of the total land in Singapore. It is clear we have a pressing need to source for alternatives.

Well, if we can't go up and across, why not go down?

Underground cities have been around for centuries. The Derinkuyu underground city in Turkey for instance is a multi-storey subterranean city that used to house as many as 20000 residents. The ancient people have cleverly crafted bathhouses and private rooms ventilated by a system of shafts. It is now a tourist attraction and some parts of it are used to store agricultural produce.

Going back to the present, many countries are exploring underground living, with Montreal’s RESO being the most successful example. Perhaps Singapore can consider moving downwards. In Singapore, we have already had a small slide of the pie of underground facilities. Nearly 80 km of MRT lines run below ground, people can do their shopping at underground malls like CityLink Mall and about 12 km of our expressways are underground. But, to shift all our houses, offices and recreational amenities permanently below the surface may be hard to swallow. Imagine taking the elevator to the basement, ten storeys below ground to go to work or school, then hop on to an MRT to travel to an underground swimming pool for your daily dose of exercise, finally, return to your home (still underground), only going up the surface for an occasional exposure to the sun.

However, land scarcity is an urgent problem and we are left with few options.

So should Singapore go under?

This blog shall explore the pros and cons of underground cities, especially how it affects our natural environment.

References:

• Singstat
• Khaw BW 2013, Exploring Exciting Possibilities Underground. http://mndsingapore.wordpress.com/. Accessed 15 August 2014.
• Starr S 2014, theguardian, How the Ancient Underground City of Cappadocia Became a Fruit Warehouse. http://www.theguardian.com/cities/2014/may/30/ancient-underground-city-cappadocia-fruit-produce-warehouse. Accessed 20 August 2014.