Abstract Knowledge of the mechanical properties of compacted bentonite is essential to assessing the performance of an engineered barrier system in a high-level radioactive waste repository. In this study, direct shear tests and uniaxial compression tests were conducted on compacted Gaomiaozi bentonite with a dry density of 1.7 g/cm3 to investigate its stiffness and strength characteristics at various initial suction levels. Specimens were found to exhibit brittle failure within an initial suction range of 11–223 MPa. The peak shear strength and shear modulus were found to increase with increasing initial suction and to begin to decrease at an initial suction of 126 MPa. The residual shear strength was found to increase with increasing initial suction within 11–223 MPa. The uniaxial compressive strength and elastic modulus were found to increase with increasing initial suction and to begin to decrease at an initial suction of 62 MPa. Models were developed to predict the stiffness and strength of the specimens as a function of the initial suction and effective stress parameter (χ). For the peak shear strength, shear modulus, uniaxial compressive strength, and elastic modulus, using the degree of saturation (Sr) and effective degree of saturation (Se) in place of χ produced the same trends which diverged from the test results at initial suction levels lower than 12 MPa and higher than 126 MPa. However, using Sr and Se in place of χ reasonably reproduced the residual shear strength within an initial suction range of 11–223 MPa. In contrast, using (Sr)α (Sr raised to an exponent α) in place of χ reproduced the test results well. For the peak shear strength, shear modulus, uniaxial compressive strength, and elastic modulus, the simulations required a value of 2.4 for the α. For the residual shear strength, the best value of α was 1.0. Based on the testing method and model approach developed in this study, the evolution of the stiffness and strength of compacted bentonite along wetting and drying paths can be further explored.

中文翻译：

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初吸力对致密高庙子膨润土刚度和强度的影响

摘要 压实膨润土的机械性能知识对于评估高放射性废物处置库中工程屏障系统的性能至关重要。在这项研究中，对干密度为 1.7 g/cm3 的压实高庙子膨润土进行了直剪试验和单轴压缩试验，以研究其在不同初始吸力水平下的刚度和强度特性。发现样品在 11-223 MPa 的初始吸入范围内表现出脆性破坏。发现峰值剪切强度和剪切模量随着初始吸力的增加而增加，并在初始吸力为 126 MPa 时开始降低。发现残余剪切强度在 11-223 MPa 内随着初始吸力的增加而增加。发现单轴抗压强度和弹性模量随着初始吸力的增加而增加，并在初始吸力为 62 MPa 时开始降低。开发了模型来预测作为初始吸力和有效应力参数 (χ) 函数的试样的刚度和强度。对于峰值剪切强度、剪切模量、单轴压缩强度和弹性模量，使用饱和度 (Sr) 和有效饱和度 (Se) 代替 χ 产生与初始吸力测试结果不同的相同趋势低于 12 MPa 和高于 126 MPa。然而，使用 Sr 和 Se 代替 χ 合理地再现了初始吸入范围 11-223 MPa 内的残余剪切强度。相比之下，使用 (Sr)α（Sr 上升到指数 α）代替 χ 很好地再现了测试结果。对于峰值剪切强度、剪切模量、单轴压缩强度和弹性模量，模拟要求 α 值为 2.4。对于残余剪切强度，α 的最佳值为 1.0。基于本研究中开发的测试方法和模型方法，可以进一步探索压实膨润土沿润湿和干燥路径的刚度和强度的演变。