Although researchers had warned about the increase in the rate of subsidence in Tehran’s 18th district in the past years, Voldkhani Street in the western border of Waliasr town, Tehran’s 18th district, faced a subsidence to a depth of 1.5 meters at the same time as the rains began, which these researchers believe has increased the subsidence risk rate in this area due to the mining of sand and construction materials and the formation of huge gravel pits and canals.
Dr. Ali Baitullahi, Director of the Earthquake and Hazards Department of the Road, Housing and Urban Development Research Center in an interview with ISNA Referring to the subsidence of the ground in the 18th district of Tehran, he said: Around midnight on Thursday, December 20, a sudden subsidence of the ground occurred on Voldkhani street in the western part of Valiasr settlement in the 18th district of Tehran. The size of the collapse area is 10 meters and the depth is 1.5 meters. It is also announced that three cars were damaged in this incident.
He stated that this incident was a sudden subsidence (collapse of the ground) and took place after the recent rains, and added: The reason for the occurrence of the ground collapse in this area is probably the flow of water in underground channels such as dry canals or natural drains, which usually after rains, causes water washing and the development of subsurface cavities, and subsequently, and mainly due to environmental vibrations, causes sudden collapses, which in Roads and residential areas are associated with the possibility of damage and injuries.
Baitullahi pointed out: The geographic coordinates of the incident point were roughly 51.340516° long, 35.633208° wide and 1108 meters high (taken from Google Earth). The figure below shows the location of Valiasr town and the approximate location of the incident area in the west of the town.
Baitullahi stated that in the case of the area south of Qaim Park, the intensification of land subsidence in this area has already been shown in a report along with the presentation of maps and figures, and continued: The accident occurred, although it was a sudden subsidence (collapse) and was probably due to subsurface erosion, which in my opinion is unrelated to the intensification of the gradual subsidence of the land in this area, due to the loosening of surface deposits due to tension and the development of possible cracks due to the gradient. Land subsidence cannot be cumulative.
The Director of Earthquake and Hazards Department of the Road, Housing and Urban Development Research Center stated that the 18th district of Tehran has a population of 444,886 people (419,249 people are within the boundaries and 25,637 people are within the boundaries). The area is located in the southwest of Tehran and is bounded from the north by Fatah highway and 45 meters from Zarand (adjacent to areas 9 and 21), from the east by Ayatollah Saeedi highway (adjacent to area 17), from the west by Azadegan highway (Quds and Shahryar cities), and from the south by Ayatollah Saeedi highway and Azadegan highway (adjacent to Islamshahr city and Chahardange city).
He emphasized: The scope of the collapse point of Omrani-Waldkhani street, the subsidence of the ground in the last two years shows a rapid rate and three times compared to the previous years, which has the appearance of an abnormal halo in the south of the park.
Map of the annual rate of land subsidence in the 18th district of Tehran and its surroundings
Stating that District 18 of Tehran is a mixed area of land with agricultural and residential, industrial and mining uses, Baitullahi said: the extraction of sand and construction materials from mines has caused the formation of huge sand pits in the area, which has aggravated the environmental risk. In addition, the presence of canals, especially their low depth in this area, has increased the risk of sudden collapses, which increases the probability of crisis events after rain. In the southern part of this area, the important Tehran-Tabriz rail route is located, which is at the intersection with the extension of the canals and the zone with an intensified rate of land subsidence.
This risk researcher pointed out: Considering the above important points, the officials of Tehran Municipality, crisis management and the officials of the railway company are requested to pay attention and sensitivity in reducing the risks of land subsidence and collapse in the 18th district of Tehran.
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