Abstract The widespread occurrence of heterogeneous mudstone poses several challenges for the stability of engineering structures. To understand the failure mechanism of argillaceous projects, and reveal the heterogeneity of mudstone, the mechanical properties of mineralogical compositions in mudstone were investigated, by using the nanoindentation technique at the meso-scale. Through “X-ray diffraction (XRD), scanning electron microscope (SEM)- energy dispersive spectrometer (EDS), and mercury intrusion porosimeter (MIP)” observations, the mineralogical compositions in mudstone can be divided into two constituents: clay matrix and silt inclusions, further, the multiscale structure model of mudstone includes three scales: macro-, meso- and micro-scale. Nanoindentation technique was adopted to investigate the meso-scale mechanical properties of mudstone by setting four peak loads ranging from 1 mN to 30 mN on different positions to avoid measuring errors. A superposition of 2 Gaussian probability densities was used to represent the distributions of the mechanical parameters of the mudstone by applying a coupled mineral-mechanical approach proposed in this study. The results showed that the mean hardness and elastic modulus of clay matrix are 398.22 MPa and 11.89 GPa, which are much smaller than that of silt inclusions (1529.43 MPa and 22.08 GPa) in mudstone, inducing the soft properties of mudstone and argillaceous projects. Due to the influence of macro- and meso-scale pores and cracks in mudstone, the elastic modulus of both the clay matrix and silt inclusions in it, is larger than that of mudstone.

中文翻译：

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泥岩细观力学性质的纳米压痕研究

摘要 非均质泥岩的普遍存在给工程结构的稳定性带来了若干挑战。为了了解泥质工程的破坏机制，揭示泥岩的非均质性，利用纳米压痕技术在细观尺度上研究了泥岩中矿物成分的力学性质。通过“X射线衍射（XRD）、扫描电子显微镜（SEM）-能谱仪（EDS）和压汞孔隙度仪（MIP）”观察，泥岩中的矿物成分可分为粘土基质和粉砂两种成分此外，泥岩多尺度结构模型包括宏观、中观和微观三个尺度。采用纳米压痕技术研究泥岩中尺度力学性质，在不同位置设置4个1 mN~30 mN的峰值载荷，避免测量误差。通过应用本研究中提出的耦合矿物-力学方法，使用 2 个高斯概率密度的叠加来表示泥岩力学参数的分布。结果表明，粘土基质的平均硬度和弹性模量分别为398.22 MPa和11.89 GPa，远小于泥岩中粉砂包裹体的硬度和弹性模量（1529.43 MPa和22.08 GPa），导致泥岩和泥质项目具有软性。由于泥岩中宏观和中尺度孔隙和裂缝的影响，其中粘土基质和粉砂包裹体的弹性模量，