Accurate description of the failure strength behaviors of rock materials, including intact rocks and jointed rock masses, is essential for engineering design and construction. First, a novel three-dimensional (3D) version of the Hoek–Brown (HB) criterion for intact rocks is proposed in this paper. A stress weighting factor n is used in this criterion to describe the effects of intermediate and minimum principal stresses. The proposed 3D version is validated using six sets of polyaxial test data, and its prediction effect is compared with that of five other existing 3D criteria. Results show that the proposed criterion exhibits the smallest prediction error for most rock types. The fitted n is closely correlated to both the partial correlation factors of intermediate and minimum principal stresses. Then, an empirical relationship m_b(β) between the material parameter m_b and joint dip angle β is developed to apply the proposed criterion to jointed rock masses. The prediction performance of the proposed empirical relation and three other existing expressions for the m_b of six jointed rock masses at different dip angles is compared, and the proposed relation exhibits the best. The performance of the proposed criterion with empirical relation m_b(β) is also verified with nine sets of conventional and true triaxial test data. Results indicate that the predicted strengths are in agreement with the test data. The expression form of the established relation m_b(β) can also accurately describe the variation in the m_b value with dip direction α.

The unique structural characteristics and special symmetry of columnar jointed rock mass result in its complex mechanical properties and strong anisotropy, which seriously affects the safety of engineering construction. To better simulate natural columnar jointed rock mass, a geometric model reconstruction method based on a single-random movement Voronoi diagram of uniform seed points using the feasible geological parameters of horizontal polygon density, irregular factor, dip angle, strike angle, transverse joint spacing, and transverse joint penetration rate is proposed in this paper. Based on this method, numerical simulation of CJRM models with varying strike angles, dip angles, and irregular factors under uniaxial compression were conducted. The results show that the uniaxial compression strengths versus strike angle and dip angle both decrease with the increase in the irregular factor, showing a U-shape and a gentle W-shape, respectively. The strength anisotropy of the strike angle decreases from 1.1057 to 1.0395 with the increase in the irregular factor, indicating relatively isotropy. With the increase int the irregular factor, the strength anisotropy of the dip angle increases from 4.3381 to 6.7953, indicating an increasing strong anisotropy at a high degree, and the effect of the irregular factor on strength behavior has the strongest and weakest impact at the dip angles of 60° and 90°, respectively.

Columnar jointed rock mass (CJRM) formed by intact rock divided by special symmetrical columnar joints is a special type of rock with poor mechanical properties, strong anisotropy, and weak self-supporting ability, severely affecting the excavation safety and stability of underground tunnels. In this study, taking the Baihetan hydropower station as the engineering background, CJRM geological numerical models with different dip angles that combined well with the natural CJRM were generated based on the geological statistical parameters of the engineering site and were verified to have high rationality and accuracy. Tunnel excavation and overloading tests were carried out on these numerical models, and the results showed that the stress and displacement distributions after excavation exhibited strong anisotropic characteristics under different dip angles, and the positions where engineering safety problems are most likely to occur are the side walls, which are prone to stress-structure-controlled failure mode. The self-supporting ability at different dip angles after excavation from weak to strong are 45°, 60°, 75°, 90°, 30°, 0°, and 15°. The safety factors assessed by overloading for CJRM with dip angles of 0–90° degrees were 2.5, 2.6, 2.6, 1.8, 2.1, and 2.2, respectively, providing a valuable reference for the construction safety and support measures of CJRM excavation.

The generation of rock mass disasters in underground engineering essentially arises from the disruption of the original three-dimensional stress equilibrium of the rock mass caused by excavation and other activities, leading to the redistribution of stress fields. During the excavation process, the engineering rock mass undergoes complex dynamic stress equilibrium processes involving loading and unloading. This equilibrium process promotes the nucleation, initiation, and propagation of pre-existing cracks in the surrounding rock, resulting in changes in the internal structure of the rock mass and a weakening of its strength. Eventually, this localized cracking extends to global failure. In order to understand the current status better and study the development trends in the study of crack propagation and evolution in defective rock, this study conducts a bibliometric analysis of 288 articles from the Web of Science Core Collection database using CiteSpace software (version 6.1.R4). The results indicate an increasing trend in the annual publication output, characterized by two phases of emergence and rapid development. The countries of China, the United States, and Iran have the highest publication output in this field. The most frequently cited journals include INT J ROCK MECH MIN, ENG FRACT MECH, and ROCK MECH ROCK ENG. This study provides a comprehensive analysis of the current status and development trends in the research on the propagation and evolution of pre-existing cracks. This study enhances the comprehension of crucial aspects of crack propagation and evolution in rock materials with defects. Moreover, it opens up new possibilities for future investigations and holds promising implications for researchers and practitioners in the field.

Disposal of landfill leachate is a critical environmental challenge due to its high pollution content. Effective treatment technologies are essential to mitigate the adverse impacts on groundwater and surrounding ecosystems. This paper employs bibliometric analysis and utilizes CiteSpace software to conduct a visual analysis of the knowledge graph of 959 research articles on "Disposal of Landfill Leachate" from the Web of Science core database for the period 1996-2022. The results indicate that the publication quantity has undergone three stages: the sprouting stage, the stable development stage, and the rapid development stage. In terms of international collaboration, China and the USA play an absolute core role. The journals Waste Management, Journal of Hazardous Materials, and Water Research are ranked among the top 3 publications in the field of landfill leachate treatment. The keyword co-occurrence clustering analysis revealed 7 clusters, including groundwater quality, heavy metals, hydrogeophysics, municipal solid, hydraulic conductivity, geochemical barriers and waste disposal, representing the primary research topics. This paper provides a comprehensive analysis of the research progress and development trends in the field of disposal of landfill leachate. It contributes to a better understanding of the key research areas and offers potential prospects for future investigations to researchers.

Dense nonaqueous phase liquid (DNAPL) is one of the main pollution sources of the underground environment. After DNAPL enters the underground environment, the migration and diffusion process has experienced a variety of media, resulting in large-scale and long-term pollution. To better understand the residual and dissolution process of DNAPL in fractures, the visual experiment of DNAPL residual and dissolution in the fracture was carried out using the transparent fracture model made of glass material, and the changes of DNAPL migration morphology and residual distribution in the crack were obtained. The results showed that the migration front of DNAPL in the fracture was finger shaped in the process of displacement of water phase by DNAPL phase, which was consistent with the state in porous media. When the process of water phase displacing DNAPL phase was over, discrete and aggregated DNAPL droplets remained in the fracture. The residual DNAPL was mainly concentrated in the area ranged from 0.3 mm to 0.8 mm. The dissolution rate of DNAPL in the fracture changed from fast to slow, and there was an obvious tailing period. The increased velocity of water phase flow significantly shortened the time of dissolution process. The DNAPL with hydrolysis reaction accounted for only 0.86% on average in the dissolution process. The findings of this study are helpful to the remediation of the underground environment.