Mechanical property characterization of mudstone based on nanoindentation technique combined with upscaling method

The poor mechanical property of mudstone seriously affects the stability of various engineering buildings. For weathered mudstone, the mechanical parameters are difficult to obtain accurately by conventional mechanical experimental methods. In addition, these macroscopic measurements cannot distinguish the mechanical response of different mineral compositions. In this study, the nanoindentation test and the data analysis method of deconvolution were used to systematically evaluate the mechanical properties of various mineral compositions in mudstone at the mesoscale. Then, three upscaling models including Mori-Tanaka (MT), Kuster-Toksoz (KT), and differential effective medium (DEM) were used to obtain the macroscopic mechanical properties. The results show that mudstone can be considered as a highly heterogeneous material with multiple mineral compositions. Among them, illite and various pores constitute the clay matrix, and quartz and feldspar minerals constitute the grain skeleton. The mechanical response of mineral compositions in the interface region was complex, mainly reflecting the composite mechanical properties of clay matrix and various clastic minerals. This characteristic made the overall mechanical properties of the mudstone show good continuity in the nanoindentation test. The Young's moduli (EIT) of the clay matrix, feldspar mineral and quartz in the mudstone were 16.1, 64.84 and 149.69 GPa respectively. The EIT of the mudstone obtained by the three upscaling models was higher than the measured macroscopic values. The model can be effectively optimized by setting the EIT of interfaces to the value of clay matrix.

Automated summary

The mechanical properties of mudstone with different mineral compositions were evaluated using nanoindentation test and deconvolution data analysis method, and the macroscopic mechanical properties were obtained using upscaling models. The results showed that mudstone exhibited high heterogeneity, and the mechanical response of mineral compositions in the interface region was complex.