Statistical studies on the pore characteristic of Qinghai-Tibet Plateau silty clay modified by nano-silica

Abstract

Abstract Nano-particles as additive materials have been widely used in geotechnical engineering, which can significantly improve the strength and suppress cracks formation of geo-materials. Nano-particle modified geo-materials consist of a ruleless distribution of soil particles, nano-particles, water, and gas. Thus, the micro-pore properties of modified geo-materials are uncertain and variable. In addition, the variability phenomenon is intensified by the strong water absorption and adhesive aggregation of nano-silica. However, the micro-pore characteristics of nano-material modified soil and the statistical properties are very limited in literature. To address those, large samples tests on Qinghai-Tibet Plateau silty clay ( ≥ 50 specimens) were conducted, and the median pore diameters and cumulative volume of pore diameters smaller than 0.1 μ m at four nano-silica contents (0, 0.75%, 2%, and 5%) were measured by the mercury intrusion porosimetry. The experimental data show that the two micro-pore parameters of fifty silty clay specimens with nano-silica additive show noticeable variability. To quantify these variablities, we assume the micro-pore diameter follows one of four probability distributions (normal, lognormal, Weibull, and gamma). The experimental curves were compared with four selected potential probability distributions and it was found that all distributions agreed well with the experimental data, approximatively. Nevertheless, only three distributions (normal, lognormal, and gamma) satisfy the Hypothesis testing. The results of chi-square test indicate that the normal distribution had the smallest effect evaluation index, and it could well describe the micro-pore parameters of nano-silica modified silty clay. The results will benefit a better understanding of the changeability of micro-pore characteristics of nano-particle modified geomaterials. Besides, these results are significant for interpreting the micromechanical mechanism of modified soils, and are helpful to guide the selection of additive materials for modified porous media.