Serious design and construction failures in Hidroituango according to reinsurer – Companies – Economy

A report revealed this Monday by La W indicates that the sum of several unresolved problems in terms of design, supervision and construction was what caused the collapses in the diversion tunnels of the Hidroituango megaproject, in Antioquia.

According to the report made by experts in geology and soil mechanics, the support installed in the Irregular Deviation Gallery (GAD) It was irregular in shape and had eroded soil, which made it easier for it to lose strength.

In addition, they assure that this occurred “between September 2017 and April 2018 due to the turbulent flow of the waters”, adding vulnerability to the stability of the tunnel, according to the report of August 2, 2019, which is hardly known.

Regarding the design problems, they highlight that the tunnels were weakened because “there were 25% less screws or rock bolts” in the GAD.

In addition, the distance between these changed from design to construction, going from 1.3 meters to 1.5 meters, which translates to “25% fewer rock screws installed in the supports.”

(Also read: EPM Board leaves Hidroituango contractors a firm lawsuit)

It is also noted that screw material changed. “They were all replaced by BAR (Bar Anchored with Resin)”, which weakened the support of the GAD.

In addition, the design did not comply with international industry standards. In fact, they assure that “the minimum ‘Q’ values ​​were not used for the types of soil that were mapped, but rather higher ones, which resulted in a recommendation of lower support than required”.

The experts also point out that the soil in the shear zone, which was eroded by the force of the water, was not protected by a special coating, since apparently, they relied on “the studies carried out by the consultancy that ensured that the average speed of the water passing through the GAD was approximately five meters per second.

On the other hand, according to the report, during the excavation the convergence of the tunnel was not correctly measured and above all, rocks fell from the roof support as construction progressed, something that from the beginning should have been taken as a signal alarm.

(More of your interest: Mapfre Seguros received from EPM a conciliation for Hidroituango policy)

Added to the design problems are those that occurred during the construction of the work, the most important of which was over-excavation, that is, the maximum excavation limits established in the contract were not met. This triggered that, in some points, “the vertical walls of seven meters of design were actually 16 meters.”

Likewise, they note that the work was progressing and “74% of the stations that measured convergence were not installed in compliance with the technical specifications of the construction.”

Furthermore, unlike what happened with the Right Diversion Tunnel (TDD) and the Left Diversion Tunnel (TDI), the GAD designs deteriorated during construction, for example, the steel mesh was replaced by a lighter one and it was not placed on the crown of the tunnel and on the side walls, but only “where required”.

The sum of these and other problems that came from the design stage and were not solved made it easier for the tunnel to weaken, giving way to the crisis of April 28, 2018, according to reinsurers.

Finally, the report emphasizes that the construction company, the consultants and the controller knew the parts of the design that were not being respected, But during the meetings they did not agree on the cause of the problems and the responsibility that each person should assume.

“Ultimately, the tunnel came into operation with all these problems, because the parties believed – wrongly – that the operation of the other two tunnels without incident for four years was sufficient proof of good design,” the report concludes.

Given these revelations, the Medellín councilor Alexánder Flórez announced that will denounce former mayor Federico Gutiérrez and former EPM manager Jorge Londoño de la Cuesta for “hiding information.”

For his part, Mayor Daniel Quintero reacted and assured that “since August 2019, with Federico Gutiérrez being mayor, Reaseguradora’s opinion was known, concluding design and construction errors in Hidroituango. The document was hidden by those interested in not suing contractors” .

This report was produced by forensic engineer Christopher Snee, geology, tunneling and construction methods expert; the expert in soil and rock mechanics, tunnel design and analysis Luis Guilherme de Mello; geology and hydrogeology expert Bernard Murphy; and Rafael Prieto, expert in soil and rock mechanics, instrumentation and monitoring, analysis of tunnels, dams, and slope stability.

(We suggest you read: -Seguros Sura is pronounced before controversy by Hidroituango

-The keys to the EPM dossier against the builders of Hidroituango)

ELTIEMPO.COM