Steady progress and bold decision making has kept excavation of the Klang Valley MRT underground section moving forward and two breakthroughs during this first week of 2015 brings the project to within three months of completing all 9.5km of 5.58m i.d. twin tube running tunnels between the seven underground stations on the city’s first 51km long MRT line for Kuala Lumpur, Malaysia.
Both breakthroughs are for the last two TBMs working on the project and with both of them working from the Pudu intermediate escape and working shaft towards Pasar Seni as the final breakthrough destination.
Breakthrough into Pasar Seni Station from Pudu by the one of eight Herrenknecht TBMs on the project in the late afternoon on 3 January completes entirely the 9.5km long southbound running tunnel from the Semantan North Portal to the Maluri South Portal. The machine is one of two EPBMs supplied by Herrenknecht and completed its final drive from Merdeka Station as its second of the eleven breakthroughs on the 9.5km long alignment.
The second breakthrough of the week, on the morning of 4 January, was for a Herrenknecht VD TBM operating in dry EPB mode to emerge into the Merdeka Station and complete its 600m drive from Pudu shaft. This machine will now be pushed through the Merdeka Station box and re-launched at the opposite end wall towards Pasar Seni Station as the very last drive and to complete the entire Northbound Tunnel with an expected arrival in mid-March 2015.
Ten TBMs - eight from Herrenknecht (six VDM and two EPBMs) and two EPBMs from CTE - were ordered and delivered to Kuala Lumpur to complete the 9.5km twin running tunnels in a planned ten drives and within the project’s 24 month tunnelling programme. All TBMs were delivered on time and the first of four Herrenknecht VD TBMs working from the impressive open cut Cochrane Station box, constructed deep into the Kuala Lumpur karst limestone, (two from each end wall) was launched in May 2013 and the fourth underway by November. The two CTE EPBMs from China also launched on time from the Semantan North Portal in June 2013 and a further two Herrenknecht VD TBMs were planned to launch at the Inai intermediate working shafts driving northwards, through Bukit Bintang Station, for final breakthrough at Pudu escape shaft, with the final two Herrenknecht EPBMs planned to drive from Pudu, through Merdeka Station, to Pasar Seni Station (Fig 1).
Plans, however, had to change, as explained by Gus Klados, Project Manager for the MMC-Gamuda JV tunnelling team that is completing central underground section of the line. “First there was a clash of programming at Pasar Rakyat Station. The TBM from Cochrane arrived early and excavation of the station was running behind so we decided to skip the planned breakthrough and continue tunnelling through the station zone to a breakthrough at Inai interim shaft.”
“The machine was progressing well,” said Klados, “and the risk of continuing for the additional 220m for a total run of 1,250m was assessed as reasonable.”
A second change came as a result of the machine’s positive progress. By extending its drive through Pasar Rakyat, it would arrive at the Inai shaft only a short time after the launch of the first machine from Inai shaft towards Bukit Bintang. With the Inai shaft being located in the difficult karstic limestone, it was decided to change plans and omit the launch of a second TBM from Inai and allow the machine from Cochrane to tunnel through and complete the drive of that Inai TBM 2 as well. “This was a case of balancing project risks,” said Klados. “The initiative allowed us to delete the underground launching galleries at the Inai shaft, which were in difficult ground, balanced against the risk of continuing a machine a further 1.8km to Pudu after completing an initial 1.2km run from Cochrane. It was confidence in the VD technology that won the day and the bold decision was taken to drive on to Pudu." The TBM that was spared the launch and excavation of the Inai to Pudu drive is owned by the MCC-Gamuda KVMRT JV and is being held in reserve, along with the seven other JV-owned TBMs on the project, for future works on the Kuala Lumpur metro masterplan. The JV has exercised the buy-back option on the two CTE supplied TBMs.
A third major decision to change the TBM sequencing was at the Pudu launch shaft. “Due to delays in the Pudu shaft construction, we wanted to mitigate the delays by launching the upper TBM in a stacked configuration first,” said Klados. “This is contrary to prevailing practice, which states that the lower tunnel must be built first and there was incredulity and rejection of the proposal initially, but in my estimation the ground, the VD machine, and the tunnelling crews, were up to this challenge and we pushed for our recommendation to launch the upper TBM first. This was needed to save us a potential six-month delay in handing over the tunnels to the track-laying teams had we waited to launch the lower tunnel TBM first.”
Eventually, explained Klados, “and with support from the contract’s supervising consultants under the leadership of Dave Parks and his team, the client, the project designers and the project insurers agreed. In addition to working properly and carefully, we also increased the monitoring density in the area to be fully aware of any cause for concern.”
As a result, the upper tunnel TBM was launched in May 2014 and completed its final breakthrough at Pasar Seni this week (3 January).
The lower tunnel TBM was launched in early November 2014 and the machine and the crews completed the first 300m section of the drive without causing any deformations to the upper tunnel. “This was a highly unusual process,” said Klados, “and it is now considered a great success. It is likely to be recorded in published technical papers and saving the six months on programme is the reward for the project.”
CEC International, a Taiwanese contractor, incorporated in Malaysia as CIMY, is subcontractor to the MCC-Gamuda JV for the EPB tunnel drives between Pudu Shaft and Pasar Seni Station. Due to reorganization of these drives, experienced MCC-Gamuda tunnelling crews were required by the client and the project’s insurers to complete the ‘undermining’ lower tunnel to Merdeka beneath the completed upper tunnel. CEC/CIMY will take over operation of the continuing VD machine at Merdeka to complete the project’s final drive to Pasar Seni and stay within the scope of the subcontract. MCC-Gamuda has seconded a number of its experienced VD TBM crews to CEC for this purpose.
These sequence and operating changes are examples of the flexibility provided when procurement of the full underground works is in the hands of one main contractor. The options would have been lost to contractual limitation, even if considered best for the project, had the alignment been procured in separate shorter contract packages. “Being a team focussed on the full extent of the underground works has allowed us to make major changes to the tunnelling sequence, as well as react to construction issues effectively and manage the risks across the underground construction procurement process as a whole,” said Graham Kennington, Head of Planning for the MCC-Gamuda KVMRT underground construction JV.
Other unusual processes were adopted to accommodate special circumstances on the project. One is particularly evident in the photo of the Pasar Seni breakthrough this week in that only half of the cutterhead is visible in the breakthrough eye. It is not a TBM steering mistake it was assured! It is explained by the fact that the end wall is not perpendicular to the tunnel axis. The reason for this, explained Klados, is that “we used the underground parking garage wall of a demolished building as part of the metro station structure. Unreasonably the designers of the previous building did not take into account the future need of the tunnellers……!”
Klados and the tunnelling team for MMC-Gamuda JV are in a good mood following the two successful breakthroughs. Work has progressed well and with one last TBM drive to complete, running tunnel excavation is on track to be completed in March 2015 and in line with the original programme to hand over the tunnels to the track laying contractor by late 2015. With work on the seven underground stations and intermediate shafts also progressing well and catching up on earlier delays, all underground civil works are on programme for completion on time by the end of 2016. With the elevated and at grade reaches of the 51km long metro line either side of the central underground section also progressing well, the project is on schedule for a completion of M&E installations and an opening of services on Phase 1 by end of 2016 and of Phase 2, with the 9.5km underground section, by mid-2017.
With those goals in sight, the Government of Malaysia has approved construction of Line 2 of the Klang Valley MRT, and MMC-Gamuda JV, with its experience and resources from Line 1, as well as its previous experience of completing the world’s iconic SMART combined road and flood control tunnel also in Kuala Lumpur, is well placed to bid successfully for the anticipated 10.2km underground section on that project. Steady progress and bold decision making has kept excavation of the Klang Valley MRT underground section moving forward and two breakthroughs during this first week of 2015 brings the project to within three months of completing all 9.5km of 5.58m i.d. twin tube running tunnels.