Investigation of swelling potential of marls (Case Study)

Abstract

The swelling behavior of marls is a complex phenomenon. In saturated state, these materials present considerable volume changes resulting in swelling and mobilizing high swelling pressures. The behavior of swelling in rocks is controlled by numerous factors acting jointly and resulting in an effect whose main agent is frequently hard to identify. The design of tunnels in swelled grounds is a difficult task. Some problems are generally met for characterization and testing marls and for prediction the response of tunnel excavation and support loading. In this research we investigate the swelling behavior of marls and analyze the effect of their physical and mechanical properties on swelling considering to a case study. Our studied samples are red and green marls that are taken from Kohrang III water conveyance tunnel project, located in Chaharmahal Province in Iran (fig. 1). Physical and mechanical properties of these rocks were determined of some laboratory tests on samples which were derived from horizontal boreholes in digged parts of the tunnel. Our results showed the role of texture, structure and mineralogy in swelling potential in marls. The comparison between these two kinds of marls indicates that the major factor in swelling of marls is their hydration. Unloading has no impact on their swelling in comparison with their mineralogical composition and the type of clay minerals. Also the results indicate that red marls are more compacted with higher resistance. Finally experimental results confirmed that compaction degree has no direct relation on swelling potential. © ISRM International Symposium - 5th Asian Rock Mechanics Symposium 2008, ARMS 2008. All rights reserved.