We pride ourselves in the work we do and how we do it
We focus in delivering the best quality in any of our work field. Our capabilities include:
As a drill and blast industry specialists, our aim is in delivering the best production drill and blast contract services.
A key pillar of Singapore’s impressive growth record was its infrastructure. Upgrading of public housing, road and rail network, underground utilities network and port facilities are regular features in Singapore’s infrastructure development. Often then not, new developments and projects are sprouting up in the build-up areas and populated neighbourhoods which requires careful planning when it comes to blasting works. During civil engineering works, such as blasting and excavation, noise and vibrations are generated which can affect residents and industrial activities in the vicinity. With the right mind-set, risk management, latest blasting product / systems and backed with the right personnel and experience, the works can be well executed with the minimal inconvenience or disruption to the neighbouring industry.
While TBMs are used in many civil tunnelling projects, the initial underground excavation for the shafts and tunnels in rock is undertaken using blasting techniques for the launching of the TBMs. These underground works require special blasting techniques and systems to effectively excavate the rock. Major projects in Singapore such as the Jurong Rock Cavern, the underground MRT lines, the Deep Tunnel Sewerage System and the Cable Tunnels require the removal of big volumes of rock during construction.
Quarry blasting for aggregates or road way construction leading into the quarry for efficient land use and space management are other reasons for blasting to effectively break large volumes of the rock in our land scarcity island. Though such blasting technique are rare these days, other similar approach of blasting large rock volumes in a single blast are undertaken for new housing and MRT projects. Such large scale blasting is perhaps one of the most challenging aspects facing the industry as population and urbanisation has brought it closer to the operating sites where large volumes of rock are encountered.
In some cases where dredging is met with extremely hard rock formation, underwater drilling and blasting operations are performed usually for harbour deepening, pipeline construction and extension of ports. With relevant experience in this field of work, we can provide the expertise to undertake the blasting works with our latest explosives products and systems.
Apart from construction blasting works, explosives are also used for geological / site characterisation projects normally termed as “seismic survey” works using explosives as a medium for the exploration of the earth’s sub-surface from the reflected seismic waves generated from the blast. Usually small charges are used for such projects and initiated individually over large span area or termed the survey lines. Other similar test are also carried out for liquefaction and calibration test based on the clients request.
Tunnelling through rock or soil is our passion and challenging projects are motivating us to deliver the contract successfully, safe and on time. We specialize in the following :
“Cross passage is a small tunnel that connects two bored tunnels. The length of the cross passage can vary depending on the alignment of the bored tunnels. Excavation profiles and diameters of cross passages depend on the geology and the purpose of the cross passage. Horse-shoe shape, square, oval or round shape are the main excavation profiles. The excavation is mainly done manually and the need for immediate shotcrete application is crucial. In hard rock conditions, rock splitting and drill&blast methods are adopted. Asia Tunnelling & Construction P/L have the knowledge, experience, machinery and experienced personnel to construct cross passages in either rock or soil conditions.”
A Pump Sump is a sump usually constructed in the bored tunnels to collect and pump out water. Various dimensions of pump sumps can be constructed, depending usually on the amount of water to be collected. Drainage pipes lead out in the pump sump and a big pump sends the water out. The construction of this structure is challenging due to the vertical excavation and working beneath the bored tunnel. Asia Tunnelling & Construction P/L have the knowledge, experience, machinery and experienced personnel to construct pump sump in either rock or soil conditions.
Mined tunnel construction is considered a special tunnelling technique in Singapore. Most tunnels in Singapore are constructed either by cut and cover method or tunnel boring machine (TBM). However, mined tunnels are very important especially when the C&C method or the bored tunnel is not feasible due to the close proximity of critical utilities such as high voltage electrical cables, gas pipes, and telecommunication cables or sewers and canals. Also, mined tunnels are often used to facilitate a launching chamber for TBMs or for small length tunnels were TBM method is too expensive.Various dimensions of mined tunnels can be constructed depending usually on the purpose of the tunnel. It can vary from a small tunnel connecting two buildings to a huge tunnel for launching a bored tunnel machine. Asia Tunnelling & Construction P/L have the knowledge, experience, machinery and experienced personnel to construct mined tunnels in either rock or soil conditions.
A shaft is a vertical tunnel. Shafts are usually constructed when there is a need to reach a formation level below surface in a restricted area. They are used for sewer constructions, tunnels, TBM launching, storage area etc. Excavation can be done manually or mechanically depending on the diameter of the shaft and the geology encountered. In hard rock conditions, rock splitting and drill&blast methods are adopted. Asia Tunnelling & Construction P/L have the knowledge, experience, machinery and experienced personnel required for shaft sinking in either rock or soil conditions.
We cover a variety of geotechnical works which are related with tunnelling and blasting works.
Rock Bolting is used for securing the rock mass from collapsing or for improving the rock stability of the excavated face. It is an additional support form and it is usually followed by shotcreting. Soil nailing has the same philosophy but is used to maintain slope stability. Both are followed by shotcreting works and have a variety of bolts and nails depending on the geology. Applications can be found at road construction, tunnel construction, deep excavations, shafts, slopes, etc. Asia Tunnelling & Construction P/L have the adequate machinery, experienced personnel and staff to successfully manage these works at the top quality.
Shotcrete spraying has a variety of applications and plays a major role in temporary support. Wet or dry method is used together with wiremesh or steel fibers to form the temporary support for geotechnical works and is commonly used in tunnel construction. Depending on the nature of works, different equipment, technics and setting up is required for the smooth and successful completion of the project. Asia Tunnelling & Construction P/L have the adequate machinery, experienced nozzlemen and staff to successfully manage shotcreting works at the top quality.
Before constructing a Cross Passage or a Pump Sump, a steel bracing has to be installed to support the bored tunnel at the location where the segment will be removed. A ring beam has the diameter of the bored tunnel but can vary in thickness and span. Usually rings beams consist of five rings that are erected at the same time and jointed together by cross beams. An opening is available at the CP or PS location for removing the segment and accessing in to the proposed structure. Erecting a ring beam requires experienced personnel as working at height and lifting of heavy beams in a confined space can cause accidents.
Once the formation level is reached in a station box, the location where the TBM will start the journey will be marked. However, the ERSS structure is still in the way and has to be demolished to facilitate the launch. A tunnel eye is a demolition job that usually requires to demolish a 1.2m thick heavily reinforced wall and assess the ground conditions behind it before the TBM launch or retrieval. Demolition works can be done mechanical or even manually depending on site conditions.
Erecting the structure for TBM launching.
Grouting is the procedure when a cement mix is pumped into a ground to improve its geotechnical characteristics and minimize the water ingress.Grouting is also used to fill up voids, gaps or pockets. Ground improvement is common in tunneling works before starting the excavation and to minimize the water ingress. Different types of grout mixes are available, depending on the geology faced at each project.
When blasting the rock formation is prohibited then non explosive technics come in action to remove the rock in sensitive areas. Alternative rock removing methods are:
“Rock splitting by mechanical means is perfect for sensitive areas or for small quantities of rock or boulders. The operation set up is relatively easy and no vibration is created therefore it is safe to use very close to structures and utility lines, pipes or sewers. The mechanical splitter can be also used to demolish concrete blocks and to pre-split sensitive areas.”
“Rock breaking using chemical means can be suitable in weak to medium-hard rocks. Chemical cartridges are used in the same manner as explosives but are not considered as high explosives and can be used in areas where explosives are restricted. The efficiency of these cartridges is not as good as using explosives, especially if using in medium-hard to hard rock conditions but can produce a higher advance rate (volume per day) than the rock splitting method.”
First stage or First bed concrete is a concrete layer which is placed between the precast segment lining and the track concrete lining cast by the track work contractor.
After completion of TBM mining, there are numerous preparations prior to this casting. They are, removing the TBM supply line, dismantling the temporary tracks, cleaning the slurry from the inverts, grinding the segments, cleaning and protecting the segment grooves and so on.
This casting work is considered as a massive concreting operation in Tunneling works.
After the first stage casting, the precast segment lining is drilled at dimple locations to install various brackets that will be used for cabling of live tunnel operation.
The brackets are fixed at the segment face by means of bolt and expansion anchors hammered into the drilled holes.
Cross passages are constructed to connect the twin tunnels, which will act as an emergency escape route; whereas the pump sumps are constructed in lower elevation of bored tunnels or of the cross passages to receive the water and will be pumped out throughout the lifespan of the bored tunnels.
The design opening is achieved by using aluminium or conventional formwork systems.