Based on long term investigations of the microstructure of various geomaterials as different as sensitive low plastic clays from Eastern Canada, unsaturated compacted silt from the Paris area, highly plastic compressible deep marine clay from the gulf of Guinea, compacted MX80 bentonite and the Callovo–Oxfordian claystone, considered as possible barriers in deep geological radioactive waste disposal, two fundamentals and distinct nano and micro mechanisms governing their macroscopic volume changes have been identified. In low plastic structured clays and dry compacted soils, in which an aggregate microstructure has been evidenced, the decrease in volume under mechanical compression result from the collapse of inter-aggregates pores in an ordered manner, from the larger to the smaller, with no effect on the intra-aggregate porosity. The soil skeleton can hence be modelled as an elastic fragile porous matrix, affected by the ordered collapse of its pores. Things are different in plastic soils, due to the significant reactivity of the montmorillonite minerals to changes in water content that results in significant changes of the initial porous matrix. The ordered adsorption of layers of water molecules in clay platelets with respect to the suction or stress applied, evidenced long time ago in Soil science through X-ray diffraction techniques, appear to be able to help better understanding various phenomena like the compression of plastic compressible soils and the hydration of compacted bentonites. Interestingly, it also applies to understand the effects of smectite minerals in the volume changes behaviour of the Callovo–Oxfordian claystone. These two mechanisms at nano and microscopic scales hence provide a better understanding of the macroscopic volume changes of a large variety of natural and compacted clayey soils and rocks.

基于对各种土工材料微观结构的长期研究，例如加拿大东部的敏感低塑性粘土，巴黎地区的不饱和压实淤泥，几内亚湾的高塑性可压缩深海粘土，压实MX80膨润土和卡洛沃-牛津粘土岩被认为是深部地质放射性废物处置的可能障碍，已经确定了两个基本原理以及控制其宏观体积变化的独特的纳米和微观机制。在低塑性结构粘土和干燥压实的土壤中（已证明存在聚集的微观结构），机械压缩作用下体积的减小是由于聚集体之间的孔以有序的方式从大到小崩溃而导致的，没有影响。骨内孔隙度。因此，可以将土壤骨架建模为弹性脆弱的多孔基质，受其孔隙有序塌陷的影响。在塑料土壤中情况有所不同，这归因于蒙脱石矿物对水含量变化的显着反应性，这导致初始多孔基质的显着变化。长期以来，通过X射线衍射技术在土壤科学中证明，相对于施加的吸力或应力，粘土分子中水分子层的有序吸附似乎能够帮助更好地理解各种现象，例如塑料可压缩物的压缩土壤和压实膨润土的水合作用。有趣的是，它也适用于了解蒙脱石矿物对卡洛沃-牛津粘土岩体积变化行为的影响。