World’s first variable density TBM makes breakthrough in Kuala Lumpur [video]

Τhe 51km long Sungai Buloh-Kajang line is the first MRT line of the Klang Valley Mass Rapid Transit (KVMRT) project that began on July 8 2011, in Kuala Lumpur, Malaysia. 9.5km of the line will be underground as well as seven of the stations. Last Thursday, on January 9 the Tunnel Boring Machine Cochrane 2 arrived at Pasar Rakyat station completing 1km route from Cochrane station, where it was launched from on July 22 last year.

The ground that the TBM was designed to dig through consisted of limestone full of karst. The tunneling contractor, taking into account the problems that had arisen in a similar karst terrain, while TBMs for stormwater management and roadway tunnel (SMART) were drilling through the cavities of limestone back in 2003, decided not to use the conventional slurry shield TBM. In the 2003 case where conventional TBMs were used, the earth support pressure in front of the machines was lost, resulting in sinkholes and soil subsidence. Thus, the contractor along with the TBM supplier opted for a variable density TBM that could change the density and viscosity of the slurry in order to adapt to any unpredictable situation. According to the general manager Ubull Din Om the variable density TBM achieved to work as it was designed, reducing soil disturbance and all tunneling work is scheduled to be completed by May next year.

Sources: THE STAR ONLINE, MRT CORP