Experimental investigations of groundwater inflow-induced piping phenonomenon in compacted bentonite buffers for HLW repository

Abstract

This study introduces a series of laboratory-scale experimental tests of piping erosion in buffer in order to investigate the phenomenon of piping erosion around the buffer material when rapid groundwater inflow occurs in a disposal repository. In a cylindrical cell, specimens of compacted bentonite were exposed to continuous water injection under varying conditions of flow rate, chemical composition, and flow direction. The erosional behaviors of bentonite buffer in piping are analyzed, including the formation of piping channels, critical inflow water pressure, and self-healing. In addition, X-ray CT scanning was utilized to analyze the post-erosion characteristics of the bentonite buffer. The outcomes will inform the development of requirements for the reference design and construction of a secure HLW repository.