By KELIN DILLON
The tragic collapse of Mexico’s Line 12 metro on May 3, which left 26 dead, was related to vital failures in the structure’s construction, said a preliminary report released by the independent Norwegian investigative authority DNV.
The Norwegian experts interviewed Mexican metro personnel including directors, coordinators, train operators and institutional security personnel to compile its comprehensive report.
The firm’s investigation determined six key failures in the construction of the line: insufficient welding process on Nelson studs, porosity and lack of fusion on the bolt-lock joint, a low number of Nelson bolts in the collapsed bridge’s beams, different types of concrete, poorly executed welds and dimensional control problems with fillet welds.
The report noted that all superficial parts of the track were working normally at the time of the crash, with “the components of the tracks, rails, cabinets and switch motors observed under normal conditions, complying with routine maintenance protocols.”
DNV’s visual inspection discovered that the trab’s steel girders were split squarely in half after the crash, an element of the structure that had been photographed as deformed over a year before the collapse.
The Norwegian firm will continue forming its expert opinion on the collapse through two further phases before coming to completely conclusive results. Ultimately, it hopes to determine if the design of the Line 12 was appropriate for safety regulations, and if the construction materials and construction methods themselves complied properly with the metro’s design.
In its quest for answers, DNV will test extracted samples from the crash, review the complete as-built construction plans of the metro, and run destructive tests and analysis on the main failure to determine if unusual overloading caused the collapse.
It is worth noting that many of the companies involved in the construction of Line 12 are also now involved in the construction of the Tren Maya tourist train in the south of Mexico.