Cross head works for the future Taman Koperasi MRT Park n Ride station of elevated package V7 (Balakong to Taman Koperasi) in progress. In the background (in front of the Petronas petrol station) is the ongoing lifting of segmental box girders and beam launching that will form the MRT elevated guideway along SILK Highway, going towards Kajang.
Since the Klang Valley Mass Rapid Transit project was launched by Prime Minister Datuk Seri Najib Tun Razak almost three years ago in July 2011, construction work for the first line is now in its most intensive phase.
WITH significant progress achieved on all fronts, construction of the Klang Valley Mass Rapid Transit (Sungai Buloh-Kajang Line) has entered a new chapter where physical infrastructure works are advancing at blazing speed.
In a report on the construction status of the SBK Line published last week, the overall completion of the SBK Line is now at 43.49%, placing the project ahead of schedule. On the other hand, tunnelling works for the 9.5km underground alignment is now more than half finished at 56%.
In the next few months, it is anticipated that progress of SBK Line’s structural works will be in its busiest pace, paving the way for the commencement of interior fit outs and systems works in the coming years.
Besides construction of piers and station portals, as well as lifting of segmental box girders that make up the elevated guideway along the elevated sections of the SBK Line, the underground segment running from Semantan towards Maluri is also fast taking shape.
“For underground works, we are now casting the superstructures of the multi-storey stations such as the station box and floor slabs. In terms of tunnelling, we have finished excavating 90% of the 7.5km high-risk karstic limestone geological formation of the underground alignment.
“One of the VD TBMs (Variable Density Tunnel Boring Machines) is expected to finish the karstic limestone section by the end of July. When both VD TBMs have entered the ‘safe zone’ of the Kenny Hill formation, we will be safely on track to complete all tunnelling works by mid-2015,” says MMC-Gamuda construction general manager Ubull Din Om.
Of the 10 TBM drives, four are already completed and are being dismantled for refurbishment and reuse for other metro tunnels.
Five other TBMS are still in the ground, with two tunnelling at Jalan Bukit Bintang towards the Bukit Bintang MRT station, two from KL Sentral MRT station towards Pasar Seni, and one from the Pudu Launch Shaft towards Merdeka. The last TBM will be launched to tunnel from the Pudu Launch Shaft towards Merdeka.
The next two months will be most critical for the underground works contractor as it needs to tunnel past the last 10% of the karstic limestone formation of the underground alignment. The challenge is to build two stacked large diameter tunnels (with an external diameter of 6.67m) across the undulating karst that is layered with the material of the Kenny Hill formation, without disturbing the fragile soil equilibrium.
“Ground condition at the interface location, which extends from the LTAT building towards the Pavilion shopping mall, under Jalan Bukit Bintang, proves to be riddled with karstic, fractured and contains cavities of mostly non-cohesive, silty top soil that is easily mobilised into movement even by slight changes of groundwater heads. The series of faults at this vicinity also result in blocky ground, which poses difficulties to the tunnelling works.
“We are on high alert 24/7 to monitor the situation and will deploy our emergency team if an incident happens,” says Ubull, adding that healthy progress is made despite the huge challenge faced and thanked all parties involved who have helped ensure the tunnelling process progresses smoothly.
Aside from the geological aspect, tunnelling underneath live traffic in Bukit Bintang is also demanding in terms of public safety as it is one of the top tourist hotspots in the heart of Kuala Lumpur, and it is surrounded by numerous office buildings, luxury hotels, age-old shoplots and high-end shopping complexes.
To ensure high responsiveness to untoward incidents, hundreds of automated settlement markers and monitoring equipment are installed at buildings located within the “zone of influence” to help surveyors determine the level of settlement that has taken place or changes in soil movement.
“With this information, we have been able to safeguard stakeholders’ safety, while at the same time tunnel effectively. Our surveillance personnel are on ground to observe abnormal changes to ground level, such as roads and pavement at all times. We are pleased that no major incidents have taken place thus far,” says Ubull, adding that where settlement was detected, best practices in safety and remedial measures were implemented, which include temporary closure of lanes and ground treatment (grouting) to stabilise the ground.
“Despite the use of the latest building protection equipment, the most advanced TBM and the most comprehensive project management expertise, Bukit Bintang remains a daunting stretch to tackle. We look forward to completing this vital stretch as uneventful as possible,” Ubull says.