نوع مقاله : مقاله پژوهشی
نویسندگان
1 استادیار زمین شناسی، پژوهشکده سوانح طبیعی، تهران، ایران
2 دانشیار گروه معماری، دانشکده معماری و شهرسازی، واحد تهران مرکزی، دانشگاه آزاد اسلامی، تهران، ایران.
کلیدواژهها
عنوان مقاله English
نویسندگان English
Introduction
Following the heavy rainfall in late 2018 and Nowruz 2019, numerous landslides have occurred in mountainous areas and slopes prone to instability in many parts of the country. The average rainfall in Iran is 250 mm. In this study, by examining the landslides that occurred in the last days of 2018 and early 2019 after floods in some provinces of the country, and using groundwater level data collected from boreholes drilled in the area of the landslides, and comparing the results obtained from stability analyses conducted in stabilizing the landslides that occurred, the effect of groundwater level changes on the occurrence of landslides and comparing the location of the landslides with the country's landslide hazard zoning map were investigated. The number of landslides caused by rising groundwater levels has also been statistically examined and determined.
Materials and methods
The research method in this study is based on library surveys and studies and field observations. In this regard, information related to the geological, tectonic and landslide conditions that occurred in the village area is examined in a library manner, and then the effects of rising groundwater levels and the occurrence of landslides are investigated, and by comparing the changes in groundwater levels and the conditions of each landslide, the effect of rising groundwater levels will be expressed. Next, a statistical study of the effect of rising groundwater levels and the percentage of landslides caused by rising groundwater levels will be conducted, and the location of landslides will be compared with the landslide zoning map of the country.
Results and discussion
Of the landslides studied in this study, 23 occurred in the Kopeh Dagh and Alborz areas. These landslides include landslides that occurred in the villages of Kashkak, Khak Pirzan, Azdaran, Qarnaveh Alia, Imam Abdullah, Belmjarak, Kafcherin, Nargeslu Alia, Goli, Arab, Qale Shaban, Sarani, Azarsei, Khanghah, Arka, CP, Estakhar Sar, Mamshi, Panu, Qale Qafeh Bala, Hossein Abad Kalposh, Narab, Kamerpasht, and Domanli in the provinces of North Khorasan, Golestan, Mazandaran, Semnan, East, and West Azerbaijan. Of the landslides studied in this study, 30 occurred in the Zagros region. These landslides include landslides that occurred in the villages of Surin, Tefin, Kish Gole Bid, Qaleh Rostam, Chal Pareh, Mobah, Abidak, Kafcherin, Garmavele Olia, Dowlat Abad, Ganjali Payin, Taleghan, Dartoot, Rah Sefid, Gol Haidar, Barfian, Deh Haidar, Manarjan, Melle Khan, Cheragh Abad, Psil, Kazem Abad, Bivand Sofli, Zarvor, Golbaghi, Cheshme Godar, Darre Sheikh Ali, Dam Bagh, Khoyeh, and Halul in the provinces of Lorestan, Kermanshah, Chaharmahal and Bakhtiari, Ilam, and Hamadan. Of the 53 landslides investigated, based on the results of excavations and borehole logs, groundwater levels were observed in boreholes drilled in the landslide area in 25 landslides, and groundwater levels were not observed in 28 drilled boreholes. According to the conducted investigations and field observations and the results of geotechnical excavations and geophysical surveys conducted in the area of the studied landslides, the type of movement in landslides has been divided into four categories: rotational, translational, rotational-translational and mudflow. Of the 53 landslides studied, 7 landslides had translational movement, 24 landslides had rotational movement, 17 landslides had rotational-translational movement and 5 landslides were mudflows.
Conclusion
Landslides occurred in the last days of 2018 and early 2019 after flooding in many provinces of the country, including North Khorasan, Golestan, Semnan, Mazandaran, Gilan, Hamedan, Lorestan, Kurdistan, Kermanshah, East and West Azerbaijan, and Zanjan. Due to the large number of landslides in rural areas of the country, the perspective of moving to another place and escaping from landslides has changed and the environment of stabilizing the landslides and in situ construction has been replaced. According to field observations during landslide occurrences and observations of groundwater levels in drilled boreholes, in 28 cases of landslides, due to intense and long-duration rainfall, instantaneous saturation of the soil mass was formed and led to landslide occurrences, in 5 cases these slope movements occurred as mudflows. In 25 cases of landslides where water level was observed in boreholes drilled at the site of the landslide mass, the rise in groundwater level (caused by intense and long-duration rainfall and its penetration into the mass) caused slope instability and landslide occurrences. It was also found that a large number of these landslides were located in the medium-risk zone, indicating that landslide activity was stimulated by rising groundwater levels.
کلیدواژهها English
