Convergence of large depth mining excavations in salt rock formations

Abstract

Measurements of the natural convergence of salt excavation at large depth exceeding 900 meters are conducted for 20 years by OBR Chemkop in Polkowice-Sieroszowice. In 2009 and 2010 the range of measurements increased to a dozen or so new stations. A long term observation of the excavation points revealed characteristic phases of the convergence phenomenon. In the first years of the salt excavations existence, values of linear convergence ranged from –100 mm/year to more than –600 mm/year. However, for excavations older than ten years, average speed of convergence varied from –30 mm/year to –100 mm/year. This is a typical graph of deformation for excavations on great depth in salt deposit.