Compacted bentonite-sand blocks have been proposed to construct buffer barriers in high-level radioactive waste (HLW) repositories in order to isolate wastes. The bentonite-based blocks are usually manufactured by uniaxial compression in mould and exhibit anisotropic behavior, which may influence the buffer performance. This current paper aims at investigating the anisotropic hydro-mechanical behavior of full-scale compacted bentonite-sand blocks. The 1/12 block rings were axially compressed in a mould with 170 and 475 mm in radiuses and 100 mm in height, and the density distribution was examined by computed tomography (CT). The block's engineering performance was monitored in different directions, including the drying shrinkage and crack development during the storage, and the swelling pressure and hydraulic conductivity during hydration. The blocks' surface shrinkage strain was measured by the digital image correlation (DIC), and the surface cracks were analyzed by an image-processing technique. In addition, subsamples were excavated from replicate blocks to measure their hydraulic conductivity and swelling pressure in different directions. The blocks showed anisotropic properties, such as the less shrinkage strain and higher swelling pressure in the vertical load direction, and the appearance of nearly horizontal cracks. In contrast, the hydraulic conductivity of the blocks was similar in the vertical and horizontal directions. The horizontally oriented smectite plates and bentonite aggregations, as verified by the scanning electron microscope (SEM) images and development of swelling pressure, contributed to blocks' anisotropic behavior. On the other hand, the sand and incompressible impurities created preferential flow paths for their isotropic permeation.

已经提出了压实的膨润土-砂块，以在高放射性废物（HLW）储存库中构造缓冲屏障，以隔离废物。膨润土基块通常在模具中通过单轴压缩制造，并表现出各向异性，这可能会影响缓冲性能。本文旨在研究全尺寸压实膨润土砂块的各向异性流体力学行为。在半径为170和475 mm，高度为100 mm的模具中将1/12挡圈轴向压缩，并通过计算机断层扫描（CT）检查密度分布。对该块的工程性能进行了不同方向的监控，包括在存储过程中的干燥收缩和裂纹发展，以及在水化过程中的溶胀压力和水力传导率。通过数字图像相关（DIC）测量块的表面收缩应变，并通过图像处理技术分析表面裂纹。另外，从重复块中挖出子样品，以测量其在不同方向上的水力传导率和溶胀压力。这些块体表现出各向异性，例如在垂直载荷方向上的收缩应变较小，溶胀压力较高，并且出现了几乎水平的裂纹。相反，这些块的水力传导率在垂直和水平方向上相似。扫描电子显微镜（SEM）图像和溶胀压力的发展证实了水平取向的蒙脱石板和膨润土的聚集体，有助于块体的各向异性行为。另一方面，