University of São Paulo: History of Tietê rectification may have contributed to the accident on the Marginal

An accident in the work of Line 6-Orange of the São Paulo Metro caused the rupture of a stretch of Marginal Tietê on February 1st. The crater formed has already been covered with concrete and part of the road is open.

In a note, the concessionaire responsible for the Metro works stated that there was a rupture of a sewage collector near the Aquinos well, which will function as a ventilation channel and emergency exit for Line 6-Orange, and that the contingency measures for the problem were sockets. The Basic Sanitation Company of the State of São Paulo (Sabesp) stated that the episode is about the rupture of a sewage superpipe.

Pedro Luiz Côrtes, professor at USP’s School of Communications and Arts (ECA) and at USP’s Institute of Energy and Environment (IEE), who is a geologist and has experience with this type of work, commented on the topic in Jornal da USP no Ar 1st Edition .

What caused the accident
“The mechanics of the entire accident are not difficult to understand and refer a little to the history of the Tietê River rectification”, says the professor. According to him, the Tietê River was not originally straight, but meandering, formed by curves. The river was transformed into a straighter channel to allow for the implementation of car lanes on its banks.

The meanders that were deactivated in this process were filled, over the years, with different materials, without controlling the quality of the filling. Because of this, the material found in these places is often poorly aggregated, a situation aggravated by the rains.

When the tunneling machine, popularly known as a tatuzão — a machine used in the excavation of subway tunnels — passes through a region, it creates vibrations, which intensify the disaggregation of this material. As a result, the sewer pipe present at the site lost support, which caused it to break.

With the pipe cracked, the sewage, in large quantities, begins to pass through this damaged area, which causes the pipe to rupture.

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