Effect of water chemistry on the hydro-mechanical behaviour of compacted mixtures of claystone and Na/Ca-bentonites for deep geological repositories  

作　　者：Zhixiong Zeng Yu-Jun Cui Jean Talandier 

机构地区：[1]Laboratoire Navier/CERMES,Ecole des Ponts ParisTech,Marne La Vallée,77455,France [2]French National Radioactive Waste Management Agency(Andra),Châtenay-Malabry,92298,France

出　　处：《Journal of Rock Mechanics and Geotechnical Engineering》2022年第2期527-536,共10页岩石力学与岩土工程学报（英文版）

基　　金：supported by Ecole des Ponts Paris Tech and the French National Radioactive Waste Management Agency(Andra);China Scholarship Council for the grant scholarship。

摘　　要：In the French deep geological disposal for radioactive wastes,compacted bentonite/claystone mixtures have been considered as possible sealing materials.After emplacement in place,such mixtures are hydrated by the site solution as well as the cement solution produced by the degradation of concrete.In this study,the effects of synthetic site solution and cement solution on the hydro-mechanical behaviour of compacted mixtures of claystone and two types of bentonites(MX80 Na-bentonite and Sardinia Cabentonite)were investigated by carrying out a series of swelling pressure,hydraulic conductivity and mercury intrusion porosimetry(MIP)tests.It was found that for the MX80 bentonite/claystone mixture hydrated with synthetic site solution,the swelling capacity was reduced compared to the case with deionised water owing to the transformation of Na-montmorillonite to multi-cation dominant montmorillonite by cation exchanges.For the Sardinia bentonite/claystone mixture,the similar increasing rate of swelling pressure was observed during the crystalline swelling process for different solutions,suggesting insignificant cation exchanges.Additionally,the cations in the synthetic site solution could reduce the thickness of diffuse double layer and the osmotic swelling for both MX80 bentonite/claystone and Sardinia bentonite/claystone mixtures.The large-pore volume increased consequently and enhanced water flow.In the cement solution,the hydroxide could also dissolve the montmorillonite,reducing the swelling pressure,and increase the large-pore volume,facilitating the water flow.Furthermore,the decrease of swelling pressure and the increase of hydraulic conductivity were more significant in the case of low dry density because of more intensive interaction between montmorillonite and hydroxide due to the high permeability.

关 键 词：Bentonite/claystone mixture Synthetic site solution Cement solution Bentonite type Swelling pressure Hydraulic conductivity 

分 类 号：TU44[建筑科学—岩土工程] TL942[建筑科学—土工工程]