Chi Li

Hydraulic fracturing (HF) and supercritical carbon dioxide (SC-CO2) fracturing are essential technologies for enhancing reservoir permeability in unconventional energy production. Determining the optimal fracturing strategy for specific reservoir conditions is a technically demanding challenge. This study conducted a thermo–hydro–mechanical (THM) coupled analysis to evaluate the mechanisms and effectiveness of HF and SC-CO2 fracturing, with emphasis on the temperature distributions, fluid dynamics, and stress fields generated. The findings indicate that SC-CO2 fracturing can generate more complex fracture networks, with breakdown pressures that are 30%–50% lower than those of HF. This is attributed to its ultralow viscosity, near-zero surface tension, and high diffusivity. Thermal effects can induce additional thermal stress, thereby increasing fracture complexity. Field studies have demonstrated that SC-CO2 fracturing can enhance production by 20%–300% compared with HF, while simultaneously reducing water consumption and promoting CO2 sequestration. Nevertheless, several challenges remain, including insufficient proppant transport efficiency, poor material compatibility, and the phase stability requirements of shallow reservoirs. This study highlights the potential of SC-CO2 fracturing as a viable alternative to HF while identifying critical gaps in field-scale implementation, thus providing a foundation for optimizing fracturing techniques across diverse geological settings.

The Yellow River Basin, as a crucial water and ecological zone, is threatened by environmental contamination from the Bayan Obo tailings dam located just 13 km away. Based on the Microbial‐Induced Calcite Precipitation, this research used a combined approach of bio‐mineralization and bio‐sorption to bio‐remediate the rare earth elements (REEs) and their mixed contaminants. Optimal conditions for soil solidification and stabilization are determined through solution pretests. Comparative analyses of adsorption, mineralization, and their combined processes were conducted in soil experiments. Evaluating using the results of speciation analysis. Following bioremediation, the adsorption–mineralization group involving indigenous bacteria, Bacillus oceanicus, exhibited the best performance. In this group, the average comprehensive reduction in exchangeable forms of Zn, Pb, La, and Ce was 52.02%, which is 2.9 times that of the adsorption group and 1.3 times that of the mineralization group under the same environmental conditions. These results indicate that the biogenic carbonates and isomorphic lattice substitutions generated through the bioption and bio‐mineralization process contribute to the solidification/stabilization of REEs and their mixed contaminants. This approach holds significant importance for environmental protection and ecological restoration in the Yellow River Basin, particularly in the middle and lower reaches of the Yellow River.

The proportion of neutral and weakly alkaline high-sulfate mine water in China is over 50%, resulting in the problem of high treatment costs. Low-cost, sustainable, and non-secondary pollution remediation technologies for in situ application in underground coal mines have rarely been reported. Here, the mixed packed and layered packed SRB-PRB (sulfate-reducing bacteria-permeable reactive barrier) column experiments at a flow speed of 300 mL/d using low-cost corncob as a carbon source were conducted to simulate sulfate in situ remediation in goafs. The column experiments utilized the simulated weakly alkaline mine water, with an initial sulfate concentration of 1027.45 mg/L. The results showed that during the 40 d operation, the SO₄²⁻ removal kinetics included three stages: rapid reduction (0–6 d), stable reduction (6–16 d), and reduction attenuation (16–40 d). Corncob could provide a relatively long-term carbon source supply, with the maximum average removal efficiency of 65.5% for the mixed packed column and 56.6% for the layered packed column. A large number of complex organic-degrading bacteria were detected in both the effluent water samples and the solid packed media, while SRB became dominant only in the solid packed media. However, the low-abundance SRB could still maintain a high-efficiency SO₄²⁻ reduction, due to the supply of readily utilizable carbon sources provided by hydrolytic and fermentative bacteria. This indicated that the synergistic effect between SRB and these organic matter-degrading bacteria was the critical limiting factor for SO₄²⁻ removal. The microscopic characterizations of SEM-EDS (scanning electron microscopy and energy-dispersive spectroscopy) and FTIR (Fourier transform infrared spectroscopy) confirmed the damage of functional groups in corncobs and the generation of SO₄²⁻ removal products (i.e., FeS). The engineering application schemes of the SRB-PRB under both in-production and abandoned mining scenarios were proposed. Additionally, the material cost estimate results showed that the SRB-PRB could achieve in situ low-cost remediation (0.2–1.55 USD/m³) of the characteristic pollutant SO₄²⁻. These findings would benefit the engineering application of in situ microbial remediation technology for high-sulfate mine water.

This study systematically investigates the failure mechanism of interfacial landslides through experimental validation and engineering applications of interfacial asperity theory. An innovative scaled physical modeling approach was developed, incorporating artificially prefabricated asperities along the sliding interface. Using 3D laser scanning to monitor slope deformation, the physical experiments provide the first direct evidence linking asperity rupture to landslide initiation. The interfacial asperity theory proves particularly effective in analyzing the three recurrent landslides along the Hushuo Expressway (2012–2017), where conventional engineering treatments failed, as all cases exhibited characteristic interfacial sliding mechanisms. The results reveal the nonlinear slip mechanisms of interfacial landslides: the first failure was controlled by asperities at the slope toe, the second by asperities at the slope crest, and the third by structural asperities. Due to post-failure excavation at the site, numerical simulations were employed to reconstruct the failure process, successfully reproducing the controlling effects of different asperity types on landslide evolution. The study also proposes the concept of targeted monitoring and early warning for interfacial landslides.The findings offer a novel theoretical perspective for understanding the progressive failure mechanisms of interfacial landslides and provide critical insights for the design of landslide mitigation measures.

Understanding and controlling the ground stress in deep coalfield mining is crucial for ensuring mine safety and efficiency. This study aims to address two unresolved scientific issues in ground stress research: the selection of optimal excavation plans and the large-scale rapid acquisition of ground stress data. A novel computational model is proposed for key rock layer control under different crustal stress conditions. The model considers the complexity and uncertainty of ground stress distribution by simplifying the key rock strata into a fixed-fixed beam model and calculating their safety through mechanical methods. Introducing an innovative approach for acquiring large-scale stress fields using GPS data. By inverting large-scale strain fields in the coalfield area, combined with World Stress Map (WSM) and measured data, accurate stress fields are obtained. The proposed optimal excavation plan can be applied to various coalfield locations worldwide, providing a scientific basis for safe and efficient mining operations. Additionally, the innovative use of GPS data in obtaining large-scale stress fields offers a valuable tool for assessing ground stress variation.