Impact of slaking shale behaviour on damage of engineering structures, Saudi Arabia

Shale slaking has caused problems on infrastructure and buildings in Tabuk City, Saudi Arabia. Most of these problems occur in the form of subsidence, cracking and loss of bearing capacity related to the slaking more than the expansion of clay minerals in shale. The aim of this research is to study the possible causes of such problems in Tabuk districts. The geotechnical properties of Tabuk shale indicate that the shale has a low degree of expansion. X-ray diffraction analysis confirms that kaolinite is the predominant clay mineral, while expansive clay minerals are not present. Based on slake durability index, disintegration ratio and shale rating system, the shale is classified as soil-like with low to medium durability. Scanning electron microscopy results indicate that the development of gypsum crystals could be a crucial factor in the degradation. Pore-air compression and crystal growth or the dissolution of gypsum and halite minerals are significant slaking mechanisms in triggering the disintegration of shale because they disturb the structure and destroy the diagenetic bonds of shale, which reduces the strength. The damage is not related to the expansion of clay minerals within the shale but is significantly influenced by the slaking of shale and its transition from rock-like to soil-like material.