For the stability and deformation analysis of open-cut mines using numerical methods, one critical step is to identify and simulate the elastoplasticity of geomaterials comprising the open-cut batters. The Victorian Brown Coal (VBC) in Australia is a non-textbook geotechnical material with a hardening feature in compression leading to brittle failure while showing a sharp post-peak softening behaviour. In order to study different aspects of elastoplasticity including the hardening and post-peak softening behaviour of the VBC, a series of laboratory tests including one-dimensional oedometer and triaxial tests were carried out on undisturbed VBC specimens taken from 30 m to 50 m below the ground level in one of the largest VBC open-cut mines in Victoria. By post-processing of the triaxial and oedometer test results, a yielding phenomenon was identified at the boundary between the fully elastic and elastoplastic domains. The magnitude of the material stiffness in the elastic domain was found to be independent of the confining pressure in triaxial tests while governed by the chemical bonding of the coal particles. The post-yield behaviour, however, was a frictional hardening and ruled by the magnitude of the confining pressure leading to a failure envelope sensitive to the organic content of the material. In this paper, a unified failure envelope is defined for the VBC using the Hvorslev-type normalisation process. Furthermore, a nonlinear elastoplastic constitutive model was examined to describe the elastoplasticity of VBC in triaxial condition, which led to a good agreement between the experimental and numerical modelling results.

中文翻译：

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根据实验室测试结果研究澳大利亚软岩的弹塑性

对于使用数值方法对露天矿进行稳定性和变形分析，一个关键步骤是识别和模拟包含露天矿面糊的地质材料的弹塑性。澳大利亚的维多利亚褐煤 (VBC) 是一种非教科书岩土材料，在压缩时具有硬化特征，导致脆性破坏，同时显示出明显的峰值后软化行为。为了研究弹塑性的不同方面，包括 VBC 的硬化和峰值后软化行为，对取自 30 m 至 50 m 的原状 VBC 试样进行了一系列实验室测试，包括一维固结仪和三轴试验。维多利亚州最大的 VBC 露天矿之一的地面。通过对三轴和固位计测试结果的后处理，在完全弹性域和弹塑性域之间的边界处发现了一种屈服现象。发现弹性域中材料刚度的大小与三轴试验中的围压无关，同时受煤颗粒的化学键控制。然而，屈服后的行为是一种摩擦硬化，由围压的大小决定，导致对材料有机含量敏感的破坏包络线。在本文中，使用 Hvorslev 型归一化过程为 VBC 定义了统一的故障包络。此外，研究了非线性弹塑性本构模型来描述三轴条件下 VBC 的弹塑性，这导致实验和数值建模结果之间具有良好的一致性。