Megaproject: Singapore’s Deep Tunnel Sewerage System | Tomorrow City | Part 1/3

Megaproject: Singapore’s Deep Tunnel Sewerage System | Tomorrow City | Part 1/3
Singapore is geologically challenged and with climate change, a growing population and economic competition – the country needs land to develop. To overcome the pervasive space challenge, the country is investing in megaprojects that will help overcome these problems and take it into the next century.

One such project is the Deep Tunnel Sewerage System. By using new technology, this infrastructure will also take Singapore’s sewage management into the next century. But tunnelling under built up areas is less than ideal. The team has to move massive tunnel boring machines that are each the length of 10 SBS buses underground. And that’s not the biggest challenge. Deep below, they have to contend with geological challenges and the ever present risk of sinkholes.

Singapore is running out of space
space to develop and prosper [Music] there are more developments now it’s
harder to find land now the little red dot is being re-engineered for the 21st century
nobody has done it before this is the only job that allows you to work on a smart city project in
singapore we are going from about 350 megawatts of
solar to two gigawatts of solar and that’s a huge jump new mega projects using state-of-the-art
technologies will harness the power of the sun it’s a kind of new for singapore to have solar
panels on water automated sports
i can’t imagine we will be developing a 60 plus both
and dig deep i did not believe the space saving part until i saw it with my own eyes
this is what engineering is to find more space and allow singapore
to flourish this is a journey into singapore’s
tomorrow city
it’s a critical moment for one of singapore’s new mega projects
one of the biggest machines on earth is being delivered to a site in the heart of singapore
a tunnel boring machine or tbm today we are lifting all the main bodies for the
just unloading at the site we do this at night because the oversized cargo is only allowed to
transport after 9 30 pm the tbm is so big that all six parts
have to be delivered one at a time
in singapore space is a luxury both on the surface and at its only landfill at
palau samacal which is reaching full capacity to create more space one project is
going underground to revolutionize waste disposal and water management
the deep tunnel sewerage system or dtss is one of singapore’s biggest
underground projects at about 7 billion us dollars this is the second phase where 19 tbms
will carve out hundreds of kilometers of tunnels underground that will take waste
water across the island to different reclamation plants
to maximize space the dtss system will be dug deeper than any existing road and
rail network at depths between 35 to 55 meters
this is one of 50 shafts the entry into the underworld
a gaping 10 meter wide hole known as shaft m it’s nearly 50 meters deep
the work site at shaft m is crammed with construction equipment and lifting supervisor johnson and his team must now
find space for these six massive parts okay stop things stop stop
wire down the space constraint is the biggest challenge for us today
2 20 am now it’s going to shift the front body lower 2 meters inwards
then we’re going to prep the cutter head unloading area with the timbers
with the heavy ss and it’s the most delicate as well
once all the sections of the tbm are delivered and unloaded they must be lowered one by one into shaft m and then
reassembled underground the most important section of the entire
tbm is the cutter head the cutter head has a diameter of 7.5
meters and comprises of dozens of heavy-duty cutting disks that chew away
at rock at a rate of approximately 3 meters every hour behind the cutter head comes the power
source the tbm is multi-purpose as the cutter head bites away this
section erects the walls of the tunnel which are made from these concrete rings
the cutter head generates huge quantities of waste or slurry and this section of the tbm is its waste disposal
system to drive the tbm forward thrust cylinders push against the newly built
tunnel rings with a force great enough to shift an elephant
the cutter head arrives [Music]
the engineers take special care unloading this spaceship-like equipment
okay swing stop stop warm up warm up
the cutter blades are precision engineered the team positions wooden blocks underneath to prevent any damage
to the blades slowly swing to your left
by the time the engineers complete the unloading dawn is breaking job well
thanks guys good job good job [Music]
it will take another six weeks of preparation before the tbm sections are
ready to be assembled in the tunnel below shaft m the deep tunnel sewerage system is not
scheduled for completion until 2025 it is being built to last for at least a
century and so engineers will inspect every detail of work during construction to
make sure nothing is overlooked one of the engineers on the inspection
team is wu lai lin
so what are they doing in the shop now today access i’ve been doing dtss since dtss one
which was completed in 2008 so yes we have been talking about the deep tunnel switch system or dtss
for many many years by the time the dtss is completed it
will free up 300 hectares of land above ground more than half of which is
currently being taken up by pumping stations and reclamation plants the 19
giant tbms still have 100 kilometers of tunnels to construct
dtss 2 follows the heavily used aya raja expressway
to get all the tbms working away below ground 50 vertical shafts must be sunk along
the route of the expressway without disrupting traffic so the first thing we do is sight the
long shafts sink the launch shafts and then we would launch the tvms from these shafts
then the tvms will tunnel along happily hopefully until they reach the retrieval shaft which is where we take out the
machines sighting shafts along the ayah raja expressway is a challenge
space is definitely one of the challenges can we find space on the surface to site our shafts or more
importantly to side the shelf big enough where we can actually launch our tunnel boring machines there are more
developments now it’s harder to find land for your shafts and things like that
at lower delta road a new piece of machinery is changing the way shafts are being constructed and saving space at
the same time it’s called the vertical shaft sinking machine or vsm
i did not believe the space saving part until i saw it with my own eyes it enables the construction of a shaft
without the need for men to be inside the shaft excavating away you can actually use it in very tight places
very close to to existing buildings
site engineer guo hao is here to check the progress one shaft has already been constructed
and another is underway so this shaft is approximately 10 meters
wide diameter and is approximately 50 meters thick
how’s the side program uh everything goes well today they’re going to finish the tie bridge
on the website so after that we’ll fill water okay starting situation
[Music] bsn that we’re currently using is the only vsm machine in asia as is
relatively new concept compared to a traditional excavation method
the system works like this first a narrow shaft is excavated to a
depth of about 10 meters then it’s lined with pre-fabricated concrete rings
now the shaft is ready for the vsm which has a telescopic arm with a road
head that can swivel around to dig deep the engineers must carefully calibrate
the robot arm before they set it to work done
so how vsm works is that there’s a cutter drum so this tattered drum will move towards the shaft in and out in and
out as if the arms will turn
is it okay [Music]
the vsm is doing vertically what the tbm or tunnel boring machine is doing
horizontally underground as soon as the cutter drum excavates a complete circle of 100 millimeters both
shaft and cutter drum will move downwards it takes at least 10 hours to dig one
meter as the ground sinks engineers will insert concrete rings that form the
shaft wall okay stop checking okay please measure the
lens okay down ready that’s all thank you very much okay okay okay
this is the last time engineers can enter the shaft once the telescopic arm
is calibrated the opening will be filled with water for the machine to begin the
excavation work [Music] this is what engineering is all about so
where we come up with solutions to reduce the risk of workers and to actually improve the efficiency of
excavation the vsm system lets the tunnelers do
their job in cramped urban sites like the one at lower delta road on the expressway
but underground the engineers will soon confront the biggest challenge of all
singapore’s subterranean geology [Music]
singapore’s planners are spending billions of dollars to build a new waste disposal system the dtss
huge tunnel boring machines are at work deep beneath our city down here the
biggest problem for the engineers is the geology the hidden world beneath our
feet so between where i’m standing now and perhaps just behind the camera
the ground conditions can differ greatly so it’s difficult for a tunnel boring machine to be catering to different
types of ground conditions that are changing so rapidly [Music]
adam switzer is a geologist at earth observatory of singapore he has spent many years studying the
geology of singapore and understands its challenges for tunnelers
tanjong rimao is one of the few places locally where the hidden world beneath
is exposed these rocks were laid down millions of years ago and over time have been
twisted and folded by the movements of the earth’s crust much of the geology of western singapore
is like this lots of different rock types very closely placed together
and very complicated in terms of folding and small faulting which means that engineering that adds a lot of
complexity so if you look here the rocks change a lot over a very short distance and
you’ve got your engineering system running in a way that drill through sandstone and all of a sudden you come
into a muddy shale like this the unit here or you run into a bed that’s full
of big boulders which we have in singapore as well then your engineering is going to run into problems
and that’s what’s happening in shaft x1 located by the benoit flyover along the
aya raja expressway irregular readings from the instruments on the tunnel boring machine or tbm
have put a stop to tunneling works well before we start our works of course
there’s a whole series of site investigations done boreholes are sunk and all that but you can only sing that
many ball holes that close apart so you have some idea of the ground conditions we are encountering so between two ball
holes you could draw a line that shows you where the rock head is but in reality you could go this this way
the exploratory boreholes were sunk here before the tunneling started
despite that ground conditions still proved tough for the cutter head to tunnel through
can you switch to the normal screen yes
we are at 2.9 bar yes
for engineer christian schilling one of the most important tasks is maintaining
the cutter head [Music] as the tbm inches forward the cutter
blades are constantly worn out and the huge machine must be stopped periodically for maintenance
and in subterranean singapore it’s a tricky operation
so this is a example of a mixed fish right yes mix of rock and soil and these are the
rock yeah and we teach the soil ah it’s very bright
i can feel that this is like like soy it’s much softer and then the one you actually have here is actually quite hot
to understand the ground conditions engineers examine samples of the rocks
excavated by the tbm and confirm that the rock face they’ve been tunneling through is made up of a
mix of hard and soft materials
[Music] at the moment we have stopped the tbm for a cutter head intervention
to carry out a cutter head intervention or chi a team of engineers enters the
space at the front of the tbm but chilling has to choose the right
moment when the ground ahead is stable and less likely to collapse on the
workers the geology let’s call it interesting up to now on this
over 500 meters we had mainly soft rock
now we are since about 200 meters in a soft geology it’s mainly clay
it’s never a good time because of course we want to continue channeling but we have to
that time we need to check what’s the level of the road and what’s the level of the soil and based on that we
prepared this place for our face map really okay
the tbm is tunneling 50 meters below sea level and the air pressure down here is
much higher than at the surface for the team it will be like diving under water and like divers they will
need to acclimatize to the pressure this particular one
we have finished changing our disk cutters that was 10 pieces this time
and now we still have some scrapers to change the soft ground tools and
then tomorrow we should be on the way again
the tbm engineers can only plan ahead if they have a good idea of the kinds of
rock and soil that the tbm must cut through as they push forward underground
geologist adam switzer and his colleagues continue to map out singapore’s subterranean world
today they’ve come to the north to investigate the mysterious sembawang springs
it’s an area famous for its 70 degrees celsius water source and
this we place the eggs here
and we leave it about one hour maybe the thing will be poured our eggs we’re a bit runny we put them
20 minutes under the hot tub but they were good it was a good day yeah and it was fun to be able to cook
them outside and in the in the water the sembawang hot springs do more than
cook runny eggs they provide vital clues to singapore’s subterranean geology
singapore isn’t known for earthquakes and volcanoes so the puzzle is where is
all this heat coming from it’s quite rare for a hot spring to occur in a setting like this you need
hot rock sauce it needs to be shallow enough that it still gets to the surface with some heat capacity and the water is
coming out here at about 70 degrees it’s it’s enough to cook eggs and so
you know that that means that that heat surface must be reasonably proximal
[Music] at the earth observatory of singapore geophysicists are using state-of-the-art
technology to solve the mystery of the springs and to look deep under the surface of
the island the hot springs are evidence of an active fault line located somewhere deep
below a fault is a fracture in the earth’s crust and here it heats groundwater that
is conveyed to the surface atsembawang to steam up those springs
faults can also become active and cause earthquakes but where exactly is this fault and
could it pose a danger for the dtss tunnelers so this kind of instrument is actually
our ears and the earthquakes or any other kind of seismic source
are like our hands patting on the watermelon so when these energy penetrating through
the earth it carries the information about the underground structure
the team positions seismometers at locations all over singapore to record
the data [Music] i’d adjust the position a bit yeah it’s
really yeah it’s working now yeah you can just take it off and then that’s it
over a period of five weeks the seismometers record vibrations from road
traffic construction and far off seismic events the result is a digital portrait of
underground singapore which they hope will pinpoint the location of any dangerous fault line this is actually in
the very high frequency so this kind of map tells us uh what
kind of frog that is under the ground so these numbers are representing
the speed of the shareway that is traveling within the earth
we can work out where this fault line is which is separating the granites in the middle and the jurong formation
sediments in the west and that’s really important when there’s construction work underground
the team will need more time to install additional sensors to figure out possible problems lying in weight for
the tunnelers with expanding built up areas and new
mega projects like the dtss the information will provide insights and
help avert disasters like the nickel highway incident in 2004
on april 20th 2004 steel supports over the circle line mrt
tunnel below the six-lane wide nickel highway collapsed the disaster triggers
a blackout and plunges traffic into chaos construction work for the circle line
had to be stopped and the highway closed for seven months for repairs
the lives of four men lost this catastrophe still serves as a
haunting reminder today
huge mega projects like the dtss are built to last into the next century
the tunnel is 22nd century technology but the project depends on one of the
oldest of all building materials concrete
and one of the most critical ingredients in that is running out
[Music] there is no limit to singapore’s
ambition to build the city of tomorrow and to free up space for the future
to achieve this the new dtss or the deep tunnel sewerage system is burrowing deep beneath
singapore to create a network of tunnels that will revolutionize waste disposal
and water management all kinds of waste will be treated reducing the amount of throwaway rubbish
and generating energy in the process the dtss will redefine recycling for the
future and take the pressure off singapore’s only landfill site at palau samacal
which is reaching full capacity but solving the problem of waste on such
a scale creates another
construction projects like the dtss are hungry for concrete
and this demand is escalating the need for a key ingredient
sand and sand is in short supply
at the nanyang environment and water research institute researcher den hui thinks he has found a
solution basically a concrete is made of a cement
and then our fine aggregates such as sand and then also cost aggregates such as pebble or bigger rocks
it’s the binding between cement and aggregates like sand that makes it strong enough to take high compressive
loads making concrete the perfect raw material for mega projects like the dtss
the sand is uh mostly in using construction at the river sand the world uses like almost like 50 billion tons of
sand every year we don’t have enough sand ten hue believes he has the answer to
the sand shortage waste he is convinced that waste can be the
new sand and a solution to better quality concrete our aim is to improve the quality of a
concrete we have this um project with nea we have this waste to energy research facility
we use a very high temperature gasification to convert waste into very stable um
classification select a new scent [Applause] the key to the process is heat high
temperatures of 1600 degrees celsius to be exact this produces gas that can be
used for power generation and the rather unattractively named slag or new sand
in this process very little is wasted [Music] this new sand is made from pure waste
we are trying to use it to replace our sand at higher ratio this leg is a very new material and we
do not know a lot of the properties about this and then currently ours are still doing the characterization and
then to understand fully this material the big question is
how does new sand compare with river sand we can see that the riverside is consists of
a lot of very fine particles with occasional large particles all the sand particles are more of like a rounded
because of the natural erosion along the rivers the consistent and rounded size
of river sand particles help them to bind easily with cement so for our new
sand the select experience that we can see very distinct um rod like structure which are known as some glass fiber and
also very angular particles
is carrying out a test to compare new sand with river sand samples
so we’re doing a 50 replacement ratio so the design mix will be 4 kg of cement and then we do um 2 kg
of sand and 2 kg of slag [Music] so we’ll be putting in the
cement and the fine aggregate into the mixer and then we’ll start the mixing process
his sample will now undergo a compressive test to see how much load or
weight they can withstand before cracking he starts with the typical concrete cube
so in the lab setting we test the amount of load it can take through the compression machine
we keep applying higher and higher compressive strength onto the concrete and then see the maximum load it can
take before it cracks or before it fails we can see that as the strength increases the deformation increase very
rapidly next ten hue tests the new sand concrete
the higher the number the more load or weight the concrete cube can take
the number to beat is 82.4
[Music] but in our new sand concrete you can see that as the strength increases in the
initial stage there is very little deformation and the winner is
nussan the superior strength of new sand is all
to do with these rod-like structures which bond with the cement
with the theory proven this new sand concrete will soon be ready to be tested in reality
at ports down road engineers have reached a critical stage in the dtss
project preparations at shaft m have been completed and it’s time to lower
the six different parts of one of the largest tbms also known as tunnel boring
machines into the completed shaft it’s a very tight squeeze
the entire process will take at least two weeks okay so means we lower down the erector
after 1 pm all right so one of the milestone is to complete
the assembly of the tbm so that we can proceed the next step which is the
mining work below ground engineers begin connecting the different
sections of the tvm the completed parts are pushed into a pre-excavated opening to make space for
the next piece then comes the second stage these gantries will house the control
cabin electrical supplies and rail tracks to transport tunnel segments as
soon as the tbm has chewed its way about 100 meters into the rock the remaining
gantries will be lowered into the shaft when completed the machine will be
130 meters long the length of 10 buses
this is one of the biggest tbms so far in singapore that’s why it needed to be segmented in a bottom part in the top
part so to make sure the alignment is correct it is all properly sealed
during the assembly we need to pay attention that all these seals are staying in place
senior project manager uli is another tunneling veteran today he has come to the portstown road
site to make sure the assembly is proceeding according to plan
it doesn’t take long for eagle eyed oolie to discover that there’s something wrong
i’ve been down to the shaft and have inspected the tightening of the bolts in the status and i’ve reported to the main contractor the boats are not tightened
we cannot confront it with a cutting wheel installation
the tbm is applying support pressure at all time to the tunnel phase from stopping it from collapsing
so if the bolts are not tightened properly there will be a leak through the
machine segment the only solution is to work through the
night to tighten the bolts all 280 of them
the next morning uli returns to the site to find out if the problem has been resolved
apparently what situation yeah we are ready so now we are
pulling up all the wire into the drum yeah we are making sure all the wires will be quite
nicely in the front okay then we’ll be ready to hook up
[Music] when the cutting wheel is just one meter
above the crater we’ll slide the front body forward so this is to prevent
damage to the rotary coupling
this is the cutting wheel the biggest and heaviest section of the tbm
its size and weight explain why uli is so cautious
we shifted the tvm backwards so that there is a big enough gap to fix the cutting wheel in front of the dbm
nevertheless it’s getting very very tight now the tricky process of lowering the
cutting wheel 50 meters down to the shaft bottom can begin and it’s a very
tight fit 500 yeah it’s very tight we have to make
sure that it’s not swinging and functioning if any part of the million dollar tbm is
damaged the consequences in terms of repair costs and delays would be
catastrophic as the operation begins
it’s all hands on deck
there’s just a five centimeter gap between the cutting wheel and the shaft
wall [Music]
the rotary coupling was actually colliding with a shield on top
[Music] but we managed to make up enough space to
fit the cutting wheel down after two hours the tbm section reaches
the bottom of the shaft safely one day late the engineers are relieved
the hardest part is over and the cutting wheel can now be attached to the front body
going underground is an important solution to singapore’s diminishing land space
a new urban scheme at punggol in northeast singapore is going to show
that putting transport links underground is a way to return city streets to the
people that use them
[Music] space is a luxury in singapore to create
more room on the surface projects are going underground but city planners have come up with
another way to tackle the problem and it’s simple
plan cities in advance to maximize space that’s the concept behind the smart city
and the first in singapore is pongol where a new district has been planned
from scratch led by gilbert chur the team has
designed a digital district which is targeted for completion in 2024
it comprises a business park and a university campus an environment where
business professionals academics students and their families can call
home so pongo drill district together with a few
other districts around singapore are one of the ideas of decentralization
to maximize space for people the planners made a crucial decision all transport links are being built
underground from the new mrt connector to huge car parks leaving the ground
level free for pedestrians and cyclists i can tell you as my favorite angle of
the model when you look at this model it’s actually right down here looking towards the west
you see the the main street which is really campus boulevard you can actually see how the business
park the sit campers are really stitched together into one very cohesive hole
so this is the whole concept of spacewalk where we are looking to have the deepest academia industry
collaboration and that’s not all
room service at the beating heart of the smart
district in pongol is a new software it’s being developed by james tan and
his team it’s called the open digital platform it allows them to test out smart systems
and real-world scenarios virtually zoom out can see the details of the
construction progress yes this is what we call a digital twin
why we do this is because we are able to have a good spatial view of
what’s happening in the real world especially when all this real-time sensor data comes in nobody has done it before this is the
only job that allows you to work on a smart city project in singapore
the idea behind the open digital platform is to integrate smart systems
with everyday life at some point we will need to integrate with the pdd meeting room system if no one is using
the room we should do a reality check that the meeting room is zero at this view i
don’t have one shot like where’s the one that’s overcrowding so
what we hope to achieve is to derive better efficiency through energy savings
and of course manpower distribution on the other hand we want to
make people’s life easier in fact we were cleaning about the idea of giving people 27 hours instead of 24 hours
because we think they can save three hours out of every day through
less waiting time faster moving into your office leaving the office and so on
while the digital team works out the smart services two meters underground another team is
spearheading the physical construction of the pongol digital district
yeah any idea on the concourse level all the shopjimmy status in preparation for the tunneling works
that will connect the digital district to the transport network
are we reaching b1 already so this one we are target to complete one month after the mrt roof completed but this is
a temporary slab so we are following closely with this construction sequence
project engineer wing zu has worked on this from the start since 2017.
we are working towards the tunnel virtual event which is a big milestone for gtc and lte collaboration
we are doing okay but of course all the consuming projects is effective i call fit but we are catching up
and she is in charge of preparing the basement works so now the machine is behind how far are
we okay the giant tbm or tunnel boring machine
that has eaten through over 700 meters of soil from the existing northeast mrt
line is about to break through right here one of the key challenges is that we are
going under a live lrt appear in a vaidar so obviously we tend to get a little bit
more uh postures hey we’re going very close make sure that we don’t affect the lrt structure
when a tbm tunnels close to critical areas underground it’s high alert for
the whole team across the project these critical points are known as influence
zones the challenge is to actually monitor the instruments in the tbm carefully so that
we can not over excavate to lead to sinkholes the
results will be very disastrous
at benoit flyover the team is on high alert two tunnel boring machines are tunneling
in close proximity to the overpass the two massive tbms working together
may destabilize the flyover so the engineers continuously monitor the structure for any signs of
weaknesses so monitoring is extremely important all our monitoring data is gathered on this
online platform so that you can access it at any time so let’s say you’re getting readings that give you maybe excessive
settlement we will be alerted please take note that our tunnel is
approaching the expressway any anomalies or significant changes please do highlight to your engineer
we are here below the flyover where it’s considered one of the critical structure for the project so along this area we
have installed three sets of instruments for each of the tbms so this will be monitored during the mining works
the risk is that as the tbms move forward underground the soil above the
tunnels compacts causing a depression to form at the surface and in the worst case scenario
develop into a sinkhole in densely packed singapore this would
be catastrophic this is a bare area and in singapore most of our areas are quite congested so
you are either underneath a road you know if not your other leaf some kind of services and everything
these instruments are part of a vital early warning system if anything is amiss
readings from the sensors are closely monitored with his decade of experience
christian schilling keeps a close eye on the progress the tbm is moving constantly forward
when we are tunneling everything okay here okay good stay on
so far no warnings from the sensors above ground so basically we see from the survey
system the the actual position of the tbm we have our navigation screen that shows
us where we are currently how far we are of the alignment
[Music] finally the tvms pass the critical risk zone and the next tunnel ring can be
back at pongo after tunneling past the vital lrt pillars the last few
centimeters are about to give way signaling the end of the mrt tunnel
and the machine’s journey everyone gathers for this momentous
fantastic breakthrough very well coordinated and very well coordinated and planned all thanks to you such a
good job
it’s a job well done for the team at pongol the moment you see the crack you know
that it’s coming next and within two minutes the whole world collapse but then you can hear all the cheering sound for everybody that’s how we live from
the entire team jtc and lta that finally we do it we have done it
dtss 2 still has four years before it will be completed
as singapore reaches for the sky building gleaming towers of glass and
steel deep below 19 giant machines continue to excavate a
network of tunnels stretching 100 kilometers this will transform how singapore
manages water and waste propelling the state into the next
century and building a new pillar of singapore’s tomorrow city

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