By rosebell
In order to constructing the northbound tunnel from Purple Line station 24 to Purple Line station 22 (Tao Poon – Rat Burana), the Terratec earth pressure balance TBM S114 will e used.
Also with the aim of completing the parallel southbound tunnel along the same route, a second Terratec EPBM, S113, will be deployed which is scheduled to be commissioned in September.
The 3.12km of twin tunnels with an internal diameter of 5.70m, two underground stations as well as three ventilation shafts, located in the heart of the capital, are the contents of contract 3.
Considering thate the alignment is placed in close proximity to the Grand Palace and numerous historic temples, it presents unique logistical and cultural challenges. The Chao Phraya River is one of the most critical sections, where the TBMs are due to bore at depths of more than 40m below ground level, through a full-face aquifer sand layer that demands precise face pressure control to ensure stability.
Additionally, the Purple Line station 23 is another key section, where the new alignment must pass directly below the existing MRT Blue Line, which was previously built using Terratec TBM S17.
For delivering 5,305kN-m of torque at up to 2.0RPM to manage any expected obstacles and overcoming these challenges, TBM S114’s 6.39m-diameter EPB shield features a 43% open ratio cutterhead with back-loading cutter bits, whereas the TBM’s thrust and active articulation system allows for up to 1.5° steering with a 160m minimum curve radius, allowing the TBM to navigate the tight curves of the alignment in Bangkok’s dense urban environment.
Moreover, Terratec’s three-way cutterhead seal protection system (labyrinth, axial, radial), ensuring reliability under high groundwater pressure, and comprehensive ground conditioning capabilities with independent foam and additive lines, grout injection, clay shock systems and bentonite emergency support, are the additional features. The advanced ring erector system, with six degrees of freedom, allows for efficient segment placement with an average assembly time of just 30 minutes per ring.
