علل و مكانيسم وقوع فروچاله ها در دشت فامنين - كبودرآهنگ

Causes and Mechanism for Occurrence of Sinkholes in Famenin-Kaboudrahang plain

Famenin-kaboudrahang plain is located in the north of Hamedan province in Iran. The sedimentary rock of the aquifer is about 70-100 meters thick and because of the excessive exploitation of the aquifer the water table goes down about 2.5-3m every year. At least 19 small and big sinkholes have been formed on the plain during the past 10 years and this has worried the inhabitants of the region. Surveys have been done and the specifications of these sinkholes are recorded. The results show that the existence of the holes, water canals, joints and fracture systems in the limy bed rock and the pumping of water from wells are the main reasons for the development of these sinkholes and other factors such as sandwashing of layers, the gas coming out from the wells and fast fall of water table are the other contributing factors. To avoid this phenomenon, drilling in the bed rock should be stopped, suitable gravel pack should be used and all wells with high water yield dug in the bed rock should be filled .