Jianming Liu

In numerous subterranean projects, the impact of groundwater on the safety of the engineering undertaking is of paramount significance. Fractures, functioning as the primary channels for seepage within subterranean rock masses, necessitate the complex and challenging task of accurately characterizing seepage patterns and quantitatively investigating the effect of fissure parameters on fluid dynamics within the rock masses. This article presents a stochastic fissure model incorporated within a finite element framework, which captures the probabilistic distribution of fissures found in nature. It provides a comprehensive analysis of the distribution of pore water pressure and Darcy velocity fields. It unveils the permeation patterns of fissured rock masses and establishes a series of fissure models, quantitatively investigating the correlations between matrix permeability, water pressure, fissure density, fissure length, the length power law, fissure angle, the dispersion coefficient, fissure aperture, and the aperture power law, as well as their influence on the equivalent permeability of the rock mass. The findings reveal that in a discrete fissured rock mass, the greater the matrix permeability, the higher the equivalent permeability, and vice versa. Under water pressures of less than 10 MPa, gravity significantly impacts equivalent permeability, and permeability linearly increases with a rise in fissure density. Longer fractures result in higher permeability, and fractures parallel to the direction of water pressure contribute most significantly to the speed of seepage. Moreover, permeability markedly increases with an increase in aperture. This study provides a comprehensive analysis of the impact of matrix permeability and fissure parameters on equivalent permeability and calculates the permeability of each model. We also propose a set of predictive formulas based on fissure geometric parameters to anticipate the permeability of rock masses.

The safety of underground engineering projects is significantly influenced by groundwater. One of the key complexities is identifying the primary seepage paths within underground rock formations, understanding the patterns of seepage, and determining the effects of fracture parameters on the fluid movement inside the rock mass. To address these issues, a probabilistic model is constructed for random fractures using the finite element method, reflecting the random nature of fracture distributions in the real world. This model allows for an in-depth examination of the distribution of pore water pressure and Darcy velocity field, revealing the permeability trends in fractured rock masses. A variety of fracture models were devised to understand the relationship between factors such as fracture density, length, length power law, angle, dispersion coefficient, aperture, and power law, and how they affect the overall permeability of rock masses. The study suggests that, in the context of discrete fractured rock masses, there is a linear increase in permeability with an increase in fracture density and aperture. Moreover, fractures of greater length lead to increased permeability, with fractures aligned with the direction of water pressure having the most impact on seepage velocity. A thorough investigation of the factors that affect each fracture parameter was performed, and the permeability of each model was computed. From these findings, a series of predictive equations were suggested for estimating rock permeability based on fracture geometry parameters.

To elucidate the physicochemical properties of the artificial silicate composite material, K-feldspar and lime were reacted in mild hydrothermal conditions (different reaction temperatures and various K-feldspar/lime ratios). Formed phases were investigated using various techniques, such as X-ray powder diffraction, the Rietveld method, scanning electron microscopy (SEM), and inductively coupled plasma-optical emission spectrometry. The analysis revealed that tobermorite, grossular (hydrogarnet), alpha-dicalcium silicate hydrate (α-C₂SH), amorphous calcium silicate hydrate, potassium carbonate, bütschliite, calcite, and calcium hydroxide formed with various conditions. Both the temperature and the Ca/Si molar ratio in the starting material greatly affected the formation of phases, especially the generation of tobermorite and α-C₂SH. The substitution of H₄O₄ ↔ SiO₄ proceeded with the increase of the Ca/Si molar ratio rather than the reaction temperature and the reaction time. More hydrogen was incorporated in hydrogarnet through the substitution of H₄O₄ ↔ SiO₄ with the increase of the Ca/Si molar ratio in the starting material. Due to the properties of tobermorite as a cation exchanger and its potential applications in hazardous waste disposal, experimental parameters should be optimized to obtain better performance of the artificial silicate composite material from K-feldspar and lime hydrothermal reaction. The dissolution mechanism of K-feldspar was also discussed.

Cd contamination of rice in recent years has aroused a nationwide concern on the potential health risk to people in China. A significant increase of soil acidification in major Chinese croplands improves available Cd content by crops, and this further pushes a heavier burden on controlling Cd contamination. Therefore, it is urgent to find a workable and green way to control Cd contamination, i.e., decrease Cd content in rice, for people’s health in China, as other countries in the world. From chemical and economic points, stabilizing/solidifying Cd may be a feasible way except in-situ ways such as removing it by the absorption of special plants and ex-situ ones such as removing the contaminated soil and treating it by special equipment. Then, it is very important how to choose a green solidifying agent. By simulating a rock-weathering process, a nano-submicron mineral-based soil conditioner (NSC) was prepared through environmentally friendly hydrothermal reaction. The application of NSC not only decreased Cd content in rice, i.e., inhibited Cd absorption, and increased pH of the soil, but also improved the content of healthy nutrients such as organic matter, available Ca, available K, available P, and available Si in the soil. The mechanism why NSC showed such good performance was also discussed in this study.