Swelling potential in Norwegian cambrosilurian shales

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Background

Black shales like Alum shale are known to pose an environmental risk when it is excavated or blasted during construction projects. The oxidation of pyrite in the shale can cause acid rock drainage with subsequent release of heavy metals into the surface- and groundwater. The Alum Shale is also known to swell when exposed to water and oxygen. Swelling can cause great damage to constructions and infrastructure many years after the construction project is finished. The mechanism behind swelling is however not well understood.

Research indicates that it is partially due to formation of calcium sulfates (gypsum, anhydrite, bassanite) when sulfate reacts with the calcium in the shale and partially due to swelling properties of clay minerals in the shale. Secondary formed ferric sulfate minerals such as jarosite can also contribute to overall swelling pressure development.

Some grey shales (Elnes formation, Furuberget formation) are also known to develop a swelling pressure when exposed to water and oxygen. These shales contain only a fraction of the sulfur that black shales do, and swelling is mainly due to hydration of swelling clays.

Aims

This master thesis aims at gaining a better understanding of the geochemical reactions that cause swelling in black and grey shales in Norway.

The goal is to gain further insight into the specific mineral reactions and quantifying the swelling pressure exerted. The ultimate goal is to develop a tool that can predict potential swelling based on chemical analyses of the parent rock material.

The study will incorporate relevant laboratory methods such as X-ray diffraction, scanning electron microscopy (SEM), mass spectrometry and lab swelling tests.

Recommended knowledge:

  • GEO4131/3131 – Geomechanics
  • Basic knowledge in chemistry (Bachelor level)
  • Basic knowledge in structural geology (Bachelor level)

Required knowledge:

  • GEO5900 – Chemical processes in soil and groundwater
Published Oct. 4, 2019 10:49 AM - Last modified Oct. 4, 2019 11:08 AM

Scope (credits)

60