Information on permeability of rock mass considering the influence of the surrounding environment is important for the geo-engineering projects such as geological disposal of radioactive waste and carbon dioxide capture and storage. Cracks and pores generally exist in rock, and fluid flow occurs through their network. However, if they are sealed, the permeability can decrease. This phenomenon is suitable considering the long-term use of a rock mass. However, the effect of sealing of cracks and pores by a chemical reaction on permeability in rock has not been sufficiently studied yet.

In this study, we investigated the effect of the sealing of cracks and pores in rock by minerals on the permeability. Especially, we investigated how calcium compounds precipitated on the rock and influenced on the permeability. For this investigation, we conducted permeability tests by using sandstone, after keeping them in environments where calcium ion concentration is high and where carbon dioxide or carbonated ion are exist. The results suggest that calcium compounds sealed pores in sandstone specimens, which caused the decrease of the porosity and the hydraulic conductivity. It has been known that in the case of a rock with a large pore diameter, pore sealing does not easily occur even if pressure is applied, and the permeability does not decrease. However, in our experiment, it was considered that pores were sealed by minerals and the hydraulic conductivity decreased. Especially, it was suggested that the hydraulic conductivity decrease significantly if carbon dioxide, used for the reaction with calcium ion, is in the state of ion in water. It is concluded that the precipitation of calcium compounds precipitated in sandstone and sealed the pores, which decreases the permeability.

1. Introduction

Information on permeability of rock mass is important for various geo-engineering projects such as carbon dioxide capture and storage and geological disposal of radioactive wastes. Cracks and pores generally exist in rock, and fluid flow occurs through their network. The permeability can decrease if they are sealed. Nara et al. (2011) shows that crack closure in rock under hydrostatic pressure decreased the permeability.

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2019. Japanese Society for Rock Mechanics. Permission to distribute - International Society for Rock Mechanics and Rock Engineering
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