Experimental investigation on the nanoindentation viscoelastic constitutive model of quartz and kaolinite in mudstone

Abstract

The creep behaviors in deep underground engineering structures, especially in soft rocks, have a remarkable impact on the long-term stability of the excavations, which finally leads to the high risk and failure of it. Accordingly, it is essential to recognize the time-dependent deformation through the investigation of this phenomenon. In this study, the creep behaviors of soft rocks were examined to help understand the underlying mechanism of the extended time-dependent deformation. Due to the limited results about the time-dependent properties of the constituents of the rock that reveal their heterogeneity, the targeting nanoindentation technique (TNIT), was adopted to investigate the viscoelastic characteristics of kaolinite and quartz in a two-constituent mudstone sample. The TNIT consists of identifications of mineralogical ingredients in mudstone and nanoindentation experiments on each identified constituent. After conducting experiments, the unloading stages of the typical indentation curves were analyzed to calculate the hardness and elastic modulus of both elements in mudstone. Additionally, the 180 s load-holding stages with the peak load of 50 mN were transformed into the typical creep strain–time curves for fitting analysis by using the Kelvin model, the standard viscoelastic model, and the extended viscoelastic model. Fitting results show that the standard viscoelastic model not only can perfectly express the nanoindentation creep behaviors of both kaolinite and quartz but also can produce suitable constants used to measure their creep parameters. The creep parameters of kaolinite are much smaller than that of quartz, which causes the considerable time-dependent deformation of the soft mudstone. Eventually, the standard viscoelastic model was also verified on the quartz in a sandstone sample.

Research on the Harmless Treatment of Weak Muddy Intercalation in Red-Bedded Soft Rock via Microwave Energy

“…Conversely, clay minerals have lower strength values than rock-forming minerals. The elastic modulus of the clay minerals ranged from 2 GPa to 17.79 GPa, and the quartz ranged from 66.54 to 121 GPa [14][15][16][17]. On the other hand, when clay minerals are exposed to water, water molecules enter the interlayer space of clay crystals, resulting in a reduction in mineral particle strength [18][19][20][21][22].…”

Mechanical Properties and Penetration Characteristics of Mudstone Slag-Based Waterproof Composites under Cyclic Loading

“…Mudstone is tightly cemented due to its fine mineral grains and the cement is mud cemented [19][20][21][22]; therefore, mudstone has low porosity [23,24], strong confinement, low permeability [25], and is a natural water barrier [26]. Abandoned mudstone is a by-product of mining production, usually located at the top of the coal seam [27].…”

The Infrared Radiation Characteristics of Sandstone Fracture Seepage under Coupled Stress-Hydro Effect

“…Therefore, it is imperative to explore the dynamic law of rock fracture and seepage under the coupled stress-hydro effect and carry out the prediction research of water damage accidents to reduce the occurrence rate of geotechnical engineering accidents. It has been found, that when the rock breaks, it usually releases electromagnetic energy [26][27][28][29][30][31], elastic energy [32][33][34][35][36][37][38][39][40][41], thermal energy [42][43][44], acoustic energy [45][46][47][48][49][50][51], and other kinds of energy [52]. Hence, generating a variety of disaster warning methods related to rock mass, such as infrared radiation method [53,54], electromagnetic radiation method [55,56], acoustic emission method [57,58], potential method [51,59] and microseismic method [60,61].…”