Giant Earth Pressure Balance Shield Tunnelling Machine Rolls Off Production Line in Tianjin, Set for Riyadh Metro Extension Works

A large-diameter earth pressure balance shield tunnelling unit, coded China Railway 1079, has completed manufacturing and rolled off the assembly line in Tianjin on 2 July, developed and built by China Railway. 

The machine boasts an excavation cutterhead diameter of 11.16 metres and an overall length of 105 metres, and is scheduled to carry out tunnelling tasks on the extension section of Riyadh Metro Line 2. It marks the first shield machine entirely manufactured in China to be shipped for engineering projects in Saudi Arabia.

The tunnel route of Riyadh Metro Line 2 extension runs through extensive stretches of clayey sand and moderately weathered limestone strata. Such ground conditions frequently trigger persistent construction hurdles including accelerated cutter wear and mud cake accumulation on cutterhead surfaces during underground excavation. 

Customised technical upgrades have been integrated into the tunnelling rig to match local geological characteristics and operational requirements laid out by the project proprietor. 

A radial ultra-high pressure water spraying system is fitted onto the cutterhead, while reinforced wear-resistant protective structures are installed across cutter tools and the screw conveyor. A new-generation segment assembling system is also embedded within the machine framework to elevate overall operational efficiency and reliability.

The full length of Riyadh Metro Line 2 extension reaches approximately 8.4 kilometres, with a 6-kilometre stretch designated for mechanical shield tunnelling. Construction activities using the newly completed tunnelling equipment will start after the machine completes factory acceptance tests and overseas shipment procedures.

Once the extended metro line becomes fully operational, it will fill gaps within Riyadh’s urban mass transit network and raise the city’s passenger transport capacity. The upgraded rail transit infrastructure will underpin long-term sustainable urban development across Riyadh, with more efficient public transport connectivity set to reshape daily commuting flows within the metropolitan zone.