Abstract：The high-alkaline pore fluid may affect buffer and sealing properties of bentonite during a long-term period in the geological radioactive waste repository. In order to investigate the dissolution and its mechanism of bentonite by hyper-alkaline pore water，the permeability and erosion tests，in which NaOH solutions is used to simulate the hyper-alkaline pore water，are carried out for the compacted Gaomiaozi bentonite samples with an initial dry density of 1.70 g/cm3；then X-ray diffraction(XRD) and energy dispersive spectrometer(EDS) are applied to investigate the alteration of mineral components and Mg content of samples. Test results present that：(1) Montmorillonite，quartz，albite and microcline(or cristobalite) are components of Gaomiaozi bentonite；and montmorillonite is the main effective component. (2) No original minerals vanish and secondary minerals produce are observed during the experiments simulating period，but values of montmorillonite and Mg content of bentonite samples decrease with the increase of concentration of the hyper-alkaline solution，which indicates the dissolution of montmorillonite under the erosion of the hyper-alkaline solutions. Therefore，under long-term infiltration of hyper-alkaline pore water，bentonite dissolves，which results in the reduce of the swelling potential，amplification of the effective porosity and permeability，and finally the buffer and sealing capability of bentonite dropping.
2012, Vol. 31 
