Influence of geotechnical parameters on dust potential of sulphate bearing clay-siltstone in tunnelling works

Abstract

Within a major tunnelling-infrastructure project in Southern Germany, the mineral anhydrite of the rock “Grabfeld Formation” (formerly “Gipskeuper”) proved to be challenging with respect to the prohibition of the use of water. Due to its bulking potential (swelling) when anhydrite interacts with water (gypsum) the use of water was prohibited during the complete process of tunnelling works. This led to significant dust production while excavating. Dust poses risk to the human respiratory system and, in order to fulfil health and safety standards and provide a safe work environment, needs to be controlled. Within this task it was monitored, whether certain geotechnical parameters of a rock influence quality and quantity of dust. Additional to tests at the construction site, a laboratory program was designed.Geotechnical tests were conducted with rock material from tunnel drives in the Grabfeld Formation. An usual LCPC device was used as dust generator. A correlation between the water content and the quality and quantity of dust can be shown. However, the point load index is(50) as an indicator of rock strength, showing a correlation with the water content, did not correlate with the quality and quantity of dust.