Research results of geotechnical properties of soils at the Podkrušnohorská výsypka dump in Sokolov brown coal field

Abstract

Open pit brown coal mining in the Sokolov coal field has been suffering with the lack of a space for overburden rocks dumping from its very beginning. The Podkrušnohorská výsypka dump is situated in a geomorphologically highly broken landscape at the Krušné Hory Mountains foot and northern part of Sokolov Basin divide. Dump rock consists of tuffaceous clays vith minimal specific resistance values QST = 0.5 - 1.0 MPa and cypric clays with minimal specific resistance values QST = 1.0 - 2.0 MPa. Large scale research works took place on the dump in various periods of time. The mining solutions of the methods on the dump were subjects of stability expert’s statements. 23 statements were produced sequentially from 1966 which were aimed to both general slopes of whole the dump and partial issues on the dump during its foundation. The dump was the scene of the series of landslides, most important of them were in the years 1986/1987 and 1990. Hydro-geological and geotechnical research was the base for stability reports and it concentrated in the dump bed quality, dump water bearing, bed water bearing, and to obtaining geotechnical parameters dump bed and dump rock fill. Basic physical and descriptive strength, transformation and technological parameters were established by in situ and laboratory tests. A long term geotechnical monitoring has been taking place on the dump – ground water level measurement, penetration measurement, dump body pore pressure measurement, inclinometric measurements in the drills, and geodetic observation of surface points of the dump.