MMC Gamuda KVMRT Sdn Bhd, project delivery partner for the second Mass Rapid Transit (MRT) line, has upgraded four new variable density tunnel boring machines (VD TBMs) to be used for the Sungai Buloh-Serdang-Putrajaya (SSP) Line, to improve their groundwork operational efficiency.

The 'VD TBM 2.0' 6.6m diameter machines, constructed by German tunnelling expert Herrenknecht Tunnelling Machinery Co. Ltd. in Guangzhou, China, will be used to construct the 13.5km underground railway portion of the 52.2km SSP Line in addition to the existing eight TBMs which were used for the first line.

MMC-Gamuda's general manager for tunnelling, Ng Hau Wei said the new machines cost between RM40 million and RM60 million depending on their specifications.

He said of the four new TBMs, two would be arriving on Malaysian shores by the year-end, after having successfully completed their factory acceptance tests (FAT) in Guangzhou.

He said the primary upgrade of the new TBMs was on the rotary crusher compartment to improve its performance in crushing hard rocks when tunnelling.

Ng said the modification also included upgrading the teeth of the cutter and its angle, as well as improving the arrangement of equipment and pipes within the shield system of the machines in order for more work to be done in the area.

"As in line one we had many blockage incidents, we have enhanced the TBMs so as to even extend their durability," he told Bernama when met in Guangzhou, recently.

In terms of tunnelling challenges for the second line, MRT Corp director of underground works for the SSP line, Blaise Mark Pearce explained that there were some tricky karstic zones where extreme caution was required and this was where the project benefited from the use of the new Variable Density TBM.

He said the newly-modified TBMs would also have to bore through granite stone, for which they had been equipped with a higher crushing capacity and bigger compressed airlock in order to allow workers to perform smoother cutter-head interventions.

"In line two, there are also granite locations, especially in the northern KL, namely the Titiwangsa area. Granite is generally hard and abrasive," he said.

For the SSP Line, three different geological profiles are involved, which are Kenny Hills and the karstic limestone and granite locations.

Pearce said 23 per cent of the underground works for the SSP Line were expected to be completed by the end of this year.

The SSP Line has 11 underground stations compared with seven spanning just 9km for the first Sungai Buloh-Kajang Line.

The line will serve as a corridor with a population of around three million stretching from Sungai Buloh to Putrajaya and will include Sri Damansara, Kepong, Batu, Jalan Sultan Azlan Shah, Jalan Tun Razak, KLCC, Tun Razak Exchange, Kuchai Lama, Seri Kembangan and Cyberjaya.

The proposed alignment is 52.2 km of which 13.5 km are underground with a total of 35 new stations.

At commencement of full service in the second quarter of 2022, the SSP Line is expected to have a ridership of 529,000 passengers per day. This is expected to further reduce the chronic traffic congestion currently faced in Kuala Lumpur.

-- BERNAMA