Specialized studies should be conducted in separate parts of Tehran in order to detect underground voids to prevent ground subsidence, or the sinking of land over man-made or natural empty spaces beneath the surface.
The Institute of Geophysics, University of Tehran, is equipped with the latest engineering devices which can be used in underground data collection and creating anomaly maps to help identify the location of underground voids and provide other useful information in this regard,” said Vahid Ebrahimzadeh Ardestani, research deputy at the institute, quoted by Tabnak news website.
Urban authorities are responsible to fill the empty spaces through cement injection to prevent any potential risk, he said. “So far tectonic studies by the institute have been conducted in Tehran Municipal districts 6 and 11, Ferdowsi St., Imam Khomeini St., Tehran metro line 1 and 2, and specific data on potential threats have been intimated to the relevant authorities.”
Unfortunately, whenever “we revert to the officials (sometimes after a long gap) to find out if our warnings have been heeded or not, we realize they have not followed up on the matter. So our studies are not implemented in practice and our effort often goes waste,” he rued.
There are over 500 networks of old ‘qanats’ or aqueducts (man-made channel constructed to send water from one location to another) in the capital stretching more than hundreds of kilometers. Some of them are at a depth of plus 130 meters while others are only 3 meters deep. Currently, due to the high number of constructions in the city, nobody knows exactly where the aqueducts are located, he said.
Land Subsidence
In some places, urban constructions have blocked underground aqueducts and streams and have created pools of standing water underground in different parts of the city. “This can lead to land subsidence which is dangerous.”
Identifying the location of the existing aqueducts and “their stabilization” can eliminate the risk of sudden sinking of the land surface owing to subsurface movement of earth materials.
According to Ali Beitollahi, an official of Housing and Building Research Center at the Ministry of Roads and Urban Development, western and southwestern parts of the capital are more prone to land subsidence. The most susceptible district to the problem is district 18 (located in southwest Tehran).
He also pointed to the issue of underground rivers and said, “Urban constructions which have blocked the water flow of some rivers have resulted in the formation of underground streams which can result in erosion of soil or rock, and ultimately cause land subsidence.
He urged urban authorities to use the results of scientific studies for proper urban planning and management.
