Anisotropic swelling pressures of compacted GMZ bentonite infiltrated with salt solutions  

作　　者：Jing Ma Yong-Gui Chen Ling-Yan Jia Wei-Min Ye Dong-Bei Wu Qiong Wang 

机构地区：[1]Department of Geotechnical Engineering,College of Civil Engineering,Tongji University,Shanghai,200092,China [2]State Key Laboratory of Disaster Reduction in Civil Engineering,College of Civil Engineering,Tongji University,Shanghai,200092,China [3]School of Chemical Science and Engineering,Tongji University,Shanghai,200092,China

出　　处：《Journal of Rock Mechanics and Geotechnical Engineering》2024年第9期3772-3785,共14页岩石力学与岩土工程学报（英文版）

基　　金：supported by the National Science Fund for Distinguished Young Scholars of China(Grant No.42125701);Innovation Program of Shanghai Municipal Education Commission(Grant No.2023ZKZD26);the Fundamental Research Funds for the Central Universities,and Top Discipline Plan of Shanghai Universities-Class I.

摘　　要：In the high-level radioactive waste(HLW)deep geological repository,bentonite is compacted uniaxially,and then arranged vertically in engineered barriers.The assembly scheme induces the initial anisotropy,and with hydration,it develops more evidently under chemical conditions.To investigate the anisotropic swelling of compacted Gaomiaozi(GMZ)bentonite and the further response to saline effects,a series of constant-volume swelling pressure tests were performed.Results showed that dry density enhanced the bentonite swelling and raised the final anisotropy,whereas saline inhibited the bentonite swelling but still promoted the final anisotropy.The final anisotropy coefficient(ratio of radial to axial pressure)obeyed the Boltzmann sigmoid attenuation function,decreasing with concentration and dry density,converging to a minimum value of 0.76.The staged evolution of anisotropy coefficient was discovered,that saline inhibited the rise of the anisotropy coefficient(Dd)in the isotropic process greater than the valley(d1)in the anisotropic process,leading to the final anisotropy increasing.The isotropic stage amplified the impact of soil structure rearrangement on the macro-swelling pressure values.Thus,a new method for predicting swelling pressures of compacted bentonite was proposed,by expanding the equations of Gouy-Chapman theory with a dissipative wedge term.An evolutionary function was constructed,revealing the correlation between the occurrence time and the pressure value due to the structure rearrangement and the former crystalline swelling.Accordingly,a design reference for dry density was given,based on the chemical conditions around the pre-site in Beishan,China.The anisotropy promoted by saline would cause a greater drop of radial pressure,making the previous threshold on axial swelling fail.

关 键 词：HLW deep geological repository Compacted GMZ bentonite Anisotropic swelling pressure Multi-scale structure Saline effect 

分 类 号：TU443[建筑科学—岩土工程]