Anisotropic microstructure would be generated in the bentonite block during unidirectional compactions. Working as buffer materials, the compacted bentonite will inevitably experience shearing processes during the long-term operation of geological repositories. In this paper, high-pressure triaxial tests were conducted on unsaturated compacted GMZ bentonite specimens with different water contents, dry densities and confining stresses, with the compaction surface of the specimens oriented in both horizontally (H-type) and vertically (V-type) configurations. Results demonstrate that an increase in water content leads to a reduction in both peak strength and residual strength, while higher confining stresses enhance these strength parameters. Normally consolidated and lightly over-consolidated bentonite specimens display substantial shear deformation, whereas heavily over-consolidated specimens tend to experience brittle failure. Water content plays a significant role in shaping both the critical state line (CSL) and the Hvorslev surface (HS), with increasing water content resulting in decreased slope parameters for both and an increased intercept parameter for the HS. Generally, V-type specimens demonstrate a steeper CSL and an outwardly extended HS in contrast to that of H-type specimens. The critical state ratio for V-type specimens is about 10 % higher, and the friction angle is 2.8° greater, than that of the H-type ones. Moreover, this difference appears to increase with increasing water content. The difference of the HS slope parameter between the two specimens is minor, while the intercept parameter is higher for the V-type specimens.

中文翻译：

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考虑各向异性的非饱和压实 GMZ 膨润土的抗剪强度特性


在单向压实过程中，膨润土块中会产生各向异性微观结构。作为缓冲材料，压实的膨润土在地质储存库的长期运行中不可避免地会经历剪切过程。本文对不同含水率、干密度和围压应力的不饱和压实 GMZ 膨润土试件进行了高压三轴试验，试件的压实面采用水平（H 型）和垂直（V 型）构型。结果表明，含水量的增加会导致峰值强度和残余强度降低，而较高的围压应力会增强这些强度参数。正常固结和轻度过度固结的膨润土试样表现出明显的剪切变形，而严重过度固结的试样往往会发生脆性破坏。含水量在塑造临界状态线 （CSL） 和 Hvorslev 表面 （HS） 中起着重要作用，含水量的增加导致两者的坡度参数减小，HS 的截距参数增加。通常，与 H 型标本相比，V 型标本表现出更陡峭的 CSL 和向外延伸的 HS。V 型试样的临界状态比比 H 型试样高约 10%，摩擦角大 2.8°。此外，这种差异似乎随着含水量的增加而增加。两个试件之间的 HS 斜率参数差异较小，而 V 型试件的截距参数较高。