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Goaf has become one of the most significant sources of hazard affecting the safety of metal and nonmetal mines. Evaluation of goaf stability is of paramount importance for mine safety production. First, 13 indices such as rock mass structure, geological structure, and goaf volume are selected based on engineering experience and literature review to assess the stability of goaf. These indices are classified according to the characteristics of each factor, and a stability evaluation system for underground mine goaf is constructed. Second, the analytic hierarchy process method based on group decision theory is utilized to calculate the subjective weight of each index. Additionally, the CRITIC method is used to calculate the objective weight of each index. Finally, game theory is used to combine the subjective and objective weights, thereby improving the accuracy of the index weight. The stability grade of the goaf is calculated using the normal cloud model. The FLAC3D numerical simulation is used to analyze the stability of the goaf and verify the accuracy of the model. The abovementioned model is utilized for assessing the stability of the goaf in the Duimenshan mine section. The results indicate that 90% of the goaf area is in a stable or relatively stable condition, while the remaining 10% is unstable. The evaluation outcomes were compared with FLAC3D numerical simulations, highlighting a scientific and reliable method with an accuracy rate of 90%.

Considering the pressure-bearing mechanism of the safety helmet and as an anchored net is subjected to the surrounding rock mass, researchers should regard the support force as a safety criterion. Thus, a method for calculating the anchored mesh support parameters (mesh width and reinforcement diameter) is proposed in this paper. The method can provide a theoretical basis for selecting the technical parameters of an anchored mesh in active support in underground engineering. Calculation results show that a strong power relationship exists between the mesh width a of the anchor net and the distance h3 from the anchor net to the top of the worker’s safety helmet, that is, a=12.891e−0.065h3, and the correlation coefficient is R2=0.947. Moreover, the mesh width of the anchored mesh decreases with an increase in the distance from the anchored mesh to the top of the worker’s safety helmet. The anchored mesh parameters designed and selected by this method ensure that the rocks falling from the anchored mesh pose no safety threat to the workers wearing helmets. The parameters also prevent an excessively large steel wire/steel bar diameter of the anchored mesh, which lowers support costs and makes the selected technical parameters of the anchored mesh economical and safe.

To effectively manage the heterogeneous and discrete knowledge of the bridge maintenance domain, this study adopts knowledge graph technology to build a knowledge base of bridge maintenance, called the bridge maintenance knowledge graph (BMKG). The BMKG uses an ontology as the knowledge organization and representation framework and a graph database as the knowledge storage tool. To facilitate the construction of the BMKG, a hybrid method combining a top-down approach and a bottom-up approach is proposed. Firstly, a bridge maintenance domain ontology (BMDO) is coded with Protégé and represented in Web Ontology Language. Secondly, rule reasoning and ontology reasoning are implemented on the BMDO in Protégé in order to automatically complete missing relations or attribute values. Thirdly, ontology reasoning is adopted to perform consistency check on the BMDO. Lastly, the BMDO model is stored in the Neo4j graph database through data format conversion, thus completing the construction of the BMKG. The BMKG is applied in a typical scenario of bridge maintenance to demonstrate its application value. Results show that the proposed hybrid method can create a knowledge graph that can realize the transformation from discrete data into interconnected knowledge. Knowledge graph offers a novel idea to create a knowledge base in the bridge maintenance domain.

In order to study the influence of elevation on the slake durability index of the quartz mica schist, the quartz mica schist with different elevations on the east slope of the Manjiazhai open-pit mine is taken as the research object, and based on laboratory tests and statistical analysis, the variation of negative correlation between the slake durability index and elevation is obtained. The disintegration mechanism of quartz mica schist at different elevations is also discussed. The test results show that the disintegration characteristics of quartz mica schist at different elevations are related to its mineral composition, fissure channel size, and rock damage effect. As the slope height increases, the ratio of mica to quartz in the rock increases, and the greater the porosity of the rock, the more fissures in the rock, the greater the permeability coefficient, and the more obvious the change of effective stress of rock under osmotic pressure. At the same time, the higher the slope elevation of open-pit mine, the longer the weathering time of rock, the higher the cumulative damage of rock, and the lower the rock slake durability index. This study provides a new idea for guiding the research on the disintegration characteristics of similar soft rock slopes in the elevation direction.

In order to verify the universal applicability of the fluid structure coupling model to the analysis requirements of deep tunnels under the MIDAS-GTS geotechnical simulation environment, the study, together with several mining enterprises, carried out verification and analysis on the measured data of 107 deep tunnels in recent years. The reference group selects the mean value of the analysis results generated by the analysis model using the preferred nonfluid structure coupling model in the MIDAS-GTS environment. Finally, it is confirmed that the fluid structure coupling model group data have significant advantages over the reference group data within the buried depth of 550 ∼ 1450 m and the tunnel cross-sectional area of 45 ∼ 102 m2. Finally, it is considered that the fluid structure coupling model has universal applicability within the analysis range. It is suggested that, in the future work, for example, when the tunnel construction project within the above analysis scope needs to carry out the simulation analysis of roof displacement and anchor bolt tension, the fluid structure coupling model should be directly selected as the analysis model.