Experimental studies show that compacted bentonite used as a backfill material for nuclear waste repository experiences strong coupling between chemical and mechanical processes. In this paper, we use a dual-structure expansive soil model, referred to as the Barcelona Expansive Model (BExM), to predict the behavior of bentonite buffer in subsurface emplacement tunnels for high-level radioactive waste. After emplacement, the bentonite is subjected to complex and coupled Thermal-Hydraulic-Mechanical-Chemical (THMC) processes. The BExM constitutive model is implemented in a multi-phase reactive transport and geomechanics simulator, TOUGHREACT-FLAC3D, and the model is verified with one benchmark test on FEBEX bentonite. We utilize a one-way Chemo-Mechanical (C-M) coupling approach, in which chemical changes affect the mechanical behavior of bentonite through the BExM linked with the evolution of mass fraction of smectite, exchangeable cation concentration, and ionic strength via osmotic suction. The parameters of the new coupled model for FEBEX bentonite are calibrated against a series of laboratory experiments with various salinity solutions. Finally, coupled THMC modeling is conducted for a generic argillite repository with bentonite buffer under high temperature, focusing on the long-term chemical change and its effect on the mechanical process.

实验研究表明，压实膨润土用作核废料处置库的回填材料，在化学过程和机械过程之间有着很强的耦合性。在本文中，我们使用一种称为巴塞罗那膨胀模型（Barcelona Expansive Model）的双重结构膨胀土壤模型来预测高放废物地下埋入隧道中的膨润土缓冲液的行为。放置后，对膨润土进行复杂且耦合的热-液压-机械-化学（THMC）工艺。BExM本构模型是在多相反应输运和地质力学仿真器TOUGHREACT-FLAC3D中实现的，并通过在FEBEX膨润土上进行的一项基准测试对该模型进行了验证。我们采用单向化学机械（CM）耦合方法，其中化学变化通过BExM影响了膨润土的机械性能，这与蒙脱石的质量分数，可交换阳离子浓度和通过渗透吸引作用产生的离子强度有关。针对FEBEX膨润土的新耦合模型，其参数已针对各种含盐溶液的一系列实验室实验进行了校准。最后，针对高温下具有膨润土缓冲液的通用皂石储存库进行了THMC耦合建模，重点是长期化学变化及其对机械过程的影响。针对FEBEX膨润土的新耦合模型，其参数已针对各种含盐溶液的一系列实验室实验进行了校准。最后，针对高温下具有膨润土缓冲液的通用皂石储存库进行了THMC耦合建模，重点是长期化学变化及其对机械过程的影响。针对FEBEX膨润土的新耦合模型，其参数已针对各种含盐溶液的一系列实验室实验进行了校准。最后，针对高温下具有膨润土缓冲液的通用皂石储存库进行了THMC耦合建模，重点是长期化学变化及其对机械过程的影响。