Weathering Characteristics of Heterogeneous Permian-Age Siltstone and Mudstone Sediments from Serbia

Abstract

This paper presents the results of an investigation of weathering characteristics of heterogeneous mudstone and shale sediments encountered during corridor X motorway construction, crossing Republic of Serbia. Red Permian braided river deposits are prone to weathering after exposure to natural climatic conditions. As a consequence of deterioration the cuttings suffered from over ten instabilities, along 12km long motorway section. In order to investigate the slaking properties of studied rock material slake durability indices along with disintegration ratio were determined. Five cycles of slake durability tests were performed. Disintegration ratio was determined in laboratory and field conditions. Field samples were exposed to natural climatic conditions during the period of one year. Slake durability index after second and fifth cycle has values between 95% < Id(2) <98% and 92% < Id(5) < 97%, respectively. Disintegration ratio determined after second and fifth cycle has values between 0.92 < DRL < 0.98 and 0.88 < DRL < 0.97, respectively. Field value of disintegration ratio of representative samples J-1(7), J-2(12) and J-3(2) after 2, 5 and 12 months of exposure amounts to 98-96-96, 92-91-86 and 92-82-70, respectively. Laboratory testing showed that material has high resistance to disintegration, thus could not be matched with field rate of slaking. Weathering of samples exposed to natural climatic conditions showed somewhat better agreement with weathering of exposed cut slopes. Observations of deterioration of samples during one year exposure gave better understanding of mechanical processes involved in rock mass deterioration.