Mexiko

Tnel Emisor Poniente II –Mechanized Excavation

Quelle/credit: Robbins

Excavation of the Tnel Emisor Poniente II in Mexico: Breakthrough into an intermediate shaft occurred on March 29. The TBM has 3.2 km left to bore |

Quelle/credit: Robbins

The ground surrounding TEP II is complex – a majority of Andesite rock gives way to valleys and fault zones, as well as a final section in soft tuff under low cover |

Quelle/credit: Robbins

The design of the Crossover XRE includes a canopy drill to consolidate ground above the TBM, as well as a separate probe drill to probe ahead and inject grout |

Quelle/credit: Robbins

Robbins Field Service personnel oversaw the Onsite First Time Assembly of the Crossover TBM, which was completed in about 12 weeks |

Quelle/credit: Robbins

Components of the 8.7 m diameter Crossover XRE TBM had to be lowered into a small 11 m wide launch shaft |

Quelle/credit: Robbins

Segment and muck storage at the small jobsite is in close completion for space |

Quelle/credit: Robbins

Continuous conveyors haul muck out of the tunnel and to a temporary storage site |

Quelle/credit: Robbins

The 5.8 km long Tnel Emisor Poniente II is lined with 350 mm thick concrete rings, and will be reinforced with a secondary lining also 350 mm thick |

Quelle/credit: Robbins

To the west of Mexico City, in the State of Mexico, a key component in a massive wastewater overhaul is underway. A 5.8 km tunnel project, known as Tnel Emisor Poniente (TEP) II, will supplement an existing wastewater line built in the 1970s and is part of a solution to a serious groundwater problem in the area.

The Valley of Mexico consists of a drained clay lake bed interspersed with volcanic rock and boulders from long dormant, buried volcanoes. Chronic groundwater depletion has resulted in soils that sink as much as 20 cm per year. All that sinking – amounting to as much as 10 m in the last century – has caused the city’s wastewater tunnels to lose their slope. The result is a recipe for massive flooding, and localized flooding each year during the rainy season.