Freeze-thaw weathering changes the pore structure, permeability, and groundwater transportation of rock material. Meanwhile, the change in rock material structure deduced by frost heaving deteriorates mechanical properties of rock material, leading to instability and insecurity of mine slopes in cold regions. In this paper, rock-like specimens containing prefabricated cracks at different angles and having undergone various freeze-thaw cycles are used as the object. Their pore structure, compressive mechanical properties, strain energies, failure characteristics, and the connection between pore structure and mechanical properties are analyzed. Results show that the porosity, spectrum area of mesopores, and spectrum area of macropores increase with the increase in freeze-thaw cycles, while crack angle shows no obvious influence on pore structure. Peak stress and elastic modulus drop with the increase in freeze-thaw cycles, while peak strain shows an increasing trend. Peak stress and elastic modulus decrease in the beginning, and then increase with the increase in crack angle, while peak strain shows a reverse trend. Elastic strain energy and pre-peak strain energy drop with the increase in freeze-thaw cycles. Elastic strain energy decreases first, and then increases with the increase in crack angle. The correlation between the spectrum area of macropores and elastic modulus is the strongest among different pores. Elastic modulus and peak stress decrease with the increase in macropore spectrum area, and peak strain increases with the increase in macropore spectrum area.

As large-scale continuous geological weak planes widely developed in deep mines, through-going discontinuities have a significant impact on the distribution of deep rock mass stress fields and the deformation and failure modes of surrounding rock and are the core factors restricting the safe and efficient extraction of deep resources. In this paper, indoor tests and numerical analysis methods were adopted to study the mechanical strength evolution characteristics and displacement changes of monitoring points of rock mass with prefabricated through-going discontinuities under horizontal and vertical pressure conditions, and the influence laws of different structural thicknesses and distances on the stress characteristics of engineering cavities were obtained. The results show that the introduction of through-going discontinuities can significantly reduce the peak strength and elastic modulus of rock specimens and change the circumferential strain. The thickness, distance, and relative position of through-going discontinuities jointly determine the strength degradation characteristics of the specimens. The larger the structural thickness (3 mm, 5 mm, and 10 mm), the weaker the strength degradation effect; when the through-going discontinuities are located above the cavity, the degradation effect is more significant. The relative position between the structure and the cavity determines the overall level of the stress field, while the structural thickness and distance (20 mm, 25 mm, and 30 mm) regulate the stress distribution and transfer path. When the through-going discontinuities are located above the cavity, the vertical stress of the surrounding rock decreases significantly with the increase of thickness, the horizontal stress remains basically stable, and the overall presents a high stress concentration characteristic. When the through-going discontinuities are located below the cavity, the vertical stress of the surrounding rock is generally low and changes gently; the horizontal stress increases gradually with the increase of thickness, and the overall stress level is much lower than that of the upper working condition.

Through-going structures are widely distributed in rock masses of underground engineering, and their dip angles act as the core factor affecting the stress field and mechanical response of surrounding rock. To reveal the mechanical mechanism of rock masses containing through-going structures with different dip angles, this study adopts a combined method of theoretical derivation, indoor model testing and numerical simulation. Firstly, a plane strain mechanical model is established to classify Tectonically-induced Stress, Residual Gravitational Stress and engineering-induced stress, and the theoretical formulas for stress components, stress residual coefficient and stress deflection angle are derived. Secondly, rock-like specimens with through-going structures of various dip angles are prepared and biaxial compression tests are carried out to monitor mechanical parameters such as surrounding rock strain and peak strength. Finally, a large-scale numerical model is built by FLAC2D (version 7.0) software to simulate the whole process of stress equilibrium and excavation unloading of rock mass under a normal stress of 20 MPa. Then the data of principal stress, stress components, stress residual coefficient and deflection angle under different dip angles are extracted. The results show that the dip angle of through-going structure exerts a prominent regulatory effect on the rock mass stress field. With the increase of the dip angle, the Tectonically-induced Stress decreases continuously while the Residual Gravitational Stress rises gradually. The variation trend of stress deflection angle is highly consistent with structural dip angle, and the influence of Residual Gravitational Stress on deflection angle is limited. Due to the differences in loading modes and model sizes between indoor tests and numerical simulations, the evolution laws of stress residual coefficient show opposite trends, but both results verify the dominant effect of structural dip angle. Combined with theoretical, experimental and numerical results, the proposed theoretical system can effectively describe the stress evolution law of rock masses with through-going structures, which provides theoretical reference and technical support for the stability analysis of surrounding rock in similar underground engineering.

The prevention and control of disasters in underground mines is a key task to ensure sustainable mining production and the development of society. The disaster chain brings cascading and clustering characteristics to disasters and leads to the expansion of their impacts and losses. It brings great difficulties to disaster prevention and control. This paper focuses on the disaster chain of a non-coal underground mine. It analyzes disaster events triggered by artificial mining activities based on a literature review, expert investigation, and field research. Subsequently, it constructs a complex network model of disaster chains containing 44 disaster nodes and 136 connecting edges. Then it performed a quantitative analysis of the complex network model, and studied complex network model parameters including degree, number of subnets, intermediate centrality, node importance, average path length, edge betweenness, connectivity, and edge vulnerability. On that basis, this paper reveals that the top five key nodes of the disaster chain are surface subsidence (H4), industrial site destruction (H7), well flooding (H21), equipment damage (H8), and living area damage (H11). It also reveals that the top five key edges of the disaster chain are mine water inrush (H6)→well flooding (H21), surface subsidence (H4)→industrial site destruction (H7), underground space failure (H3)→industrial site destruction (H7), gob collapse (H2)→surface subsidence (H4), and gob collapse (H2)→landslide (H5). Finally, this paper proposes specific chain-breaking disaster mitigation measures. Implementing these actions can play a pivotal role in mitigating the impact of mine disasters, preserving lives, and sustaining regional prosperity.