Bentonite pellet mixtures are considered as one of the candidate sealing materials for deep geological disposals of radioactive waste. One of the particularities of this material is the initial heterogeneous distribution of pellets and porosity within the mixture, leading to complex hydro-mechanical behaviour. In this paper, the hydro-mechanical properties of GMZ bentonite pellet mixtures were investigated in the laboratory by carrying out water retention tests on pellet mixtures under constant-volume condition and single pellets under free swelling condition, as well as a infiltration test on a column specimen of pellet mixture. In the infiltration test, the relative humidity and radial swelling pressure were monitored at five heights, the axial swelling pressure was also recorded. The instantaneous profile method was applied to determine the unsaturated hydraulic conductivities. Results show that, in high suction range (> 10 MPa) the water retention curve of pellet mixture under constant-volume condition was comparable to that of a single pellet under free swelling condition, while in low suction range (< 10 MPa) the latter exhibits a much higher water retention capacity. Due to clogging of large pores, the unsaturated hydraulic conductivity decreases as suction decreases to around 25 MPa. However, with further suction decrease, the hydraulic conductivity increases continuously until the value at saturated state, as in the case of most unsaturated soils. The radial swelling pressure at different heights develops with local sudden increase and decrease, which was attributed to local rearrangement of pellets upon wetting. By contrast, as the axial swelling pressure was measured on the global surface of the specimen, it develops in a more regular fashion.

中文翻译：

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GMZ膨润土颗粒混合物的水-力学行为研究

膨润土颗粒混合物被认为是放射性废物深地质处置的候选密封材料之一。这种材料的特点之一是粒料的最初不均匀分布和混合物中的孔隙率，导致复杂的水力行为。本文在实验室中通过对恒体积条件下的颗粒混合物进行保水试验，并在自由溶胀条件下对单个颗粒进行了保水试验，并在柱上进行了渗透测试，从而研究了GMZ膨润土颗粒混合物的水力学性能。颗粒混合物的标本。在渗透测试中，在五个高度处监测相对湿度和径向膨胀压力，还记录轴向膨胀压力。应用瞬时剖面法确定非饱和水导率。结果表明，在高吸力范围（> 10 MPa）下，恒定体积条件下粒料混合物的保水曲线与自由溶胀条件下的单个粒料的保水曲线相当，而在低吸力范围（<10 MPa）下后者表现出更高的保水能力。由于大孔的堵塞，当吸力降低到25 MPa左右时，不饱和水力传导率降低。但是，随着吸力的进一步降低，与大多数不饱和土壤一样，水力传导率持续增加，直到达到饱和状态的值为止。不同高度的径向膨胀压力随着局部突然增加和减少而发展，这归因于润湿时颗粒的局部重排。相比之下，由于在样品的整体表面上测量了轴向膨胀压力，因此它以更规则的方式发展。