Comprehensive tests were conducted on a longwall face in China to study mining-induced strata movement and fractures. The first and periodic weightings of the main roof were both captured by microseismic (MS) monitoring and support resistance recording and were 64 and 20 m, respectively. Based on the fracture detection through hydrological observations in a borehole, the roof is clearly divided into three zones: water-conductive zone, horizontal fracture, and continuous zone. Following the field investigation, an innovative finite-difference method (FDM) and distinct-element method (DEM) coupled numerical simulation method was proposed, which features simulating the progressive failure of the rock mass from intact to blocky. The numerical study shows that the proposed coupled method can give reasonable explanations for all in situ tests and handle the progressive caving of the rock layers, as well as the accompanying MS activities and response of the hydraulic supports. The proposed coupled method has advantages over a continuum or discrete method in coal mining simulation. Compared with a continuum method, the coupled method can simulate the deformation and collapse of the overburden strata, whereas the continuum method is only applicable before the first weighting of the rock layer, after which it gives wrong results. In contrast, compared with a discrete method where the blocks are factitiously set before and their sizes are mandatory, the coupled method allows the blocks to form automatically based on the failure state of the rock mass.

Water inrush disasters in mining frequently occur under the influence of confined water‐bearing fault zones. Therefore, investigating the fault water inrush mechanism is necessary to reduce the number of occurrences of this type of disaster. In fault zones, the rock is highly fractured, and the mechanism of water conduction is complex. In this research, the seepage mechanism of fractured sandstone in fault zones is studied through experiments, and the results indicate that the permeability coefficient of fractured sandstone depends on the axial stress and particle size. The relationship between the permeability coefficient and axial stress was an exponential relationship. Then, a water‐rock coupled model is proposed based on the experimental results, which considers the different water flow patterns during water inrush disasters. Finally, a numerical simulation combined with the water‐rock coupled model is conducted to investigate the fault water inrush mechanism of a case study, and the results reveal that when water inrush disasters occur during mining, two types of conditions are required. One is that the connection among the fractured zone of the coal seam roof, fault fracture zone, and aquifer fails, and the other is that the connection among the fractured zone of the water inrush prevention pillar, fault fracture zone, and aquifer fails. This study contributes to an increased understanding of the mechanism of water inrush disasters and the design of water inrush prevention pillars.

Rock engineering is usually associated with impact loads induced by blasting, drilling, vibration, or earthquake. In the engineering fields of tunnelling, slopes, dams, and mining, rocks are always subjected to cyclic wet‐dry caused by periodical variation in moisture. To study cyclic wet‐dry effects on dynamic compression properties and deterioration of red‐sandstone, physical tests and dynamic and static tests were conducted after 0, 5, 10, 15, and 20 wet‐dry cycles. Changes in physical and mechanical parameters, including P‐wave velocity, density, and static and dynamic compression strength, were determined. Deterioration of red‐sandstone caused by wet‐dry cycles was verified through physicomechanical parameters, and the microscopic features were scanned by SEM techniques. Experimental results showed that the dynamic compression strength increased with the loading rate, but decreased with the increase of wet‐dry cycles. In terms of the loading rate, the decay function model was proposed to evaluate the long‐term dynamic compression strength of red‐sandstone against cyclic wet‐dry action. Besides, the function of the loading rate was obtained. Parameters of two models, decay constant and half‐life values, were measured accurately.

In the engineering fields of mining, tunneling, slopes, and dams, rocks are usually subject to the coupling effect of impact load and wet‐dry cycles. The deformation rule of rocks under the coupling effects is a symbolic mechanical property, which lays the foundation for the design and evaluation in the rock engineering. In this paper, the coupling damage was classified as mesodamage induced by wet‐dry cycles and macrodamage induced by impact load, and the loading rate effect was considered as the load damage. Besides, a constitutive model of coupling damage was concluded based on Lemaitre’s strain equivalent assumption. Consequently, the validity of the model was verified by a series of dynamic compression tests of red sandstone. Results indicated that the proposed damage constitutive model can definitely describe the dynamic stress‐strain curves of red sandstone after wet‐dry cycles and impact load. The evolution of coupling damage curves showed that wet‐dry cycle damage plays a dominant role in the elastic deformation stage, while the yield failure stage is controlled by the load damage in which the loading rate cannot be ignored. Parametric study was also performed to analyze the effect of parameters on dynamic stress‐strain curves. The proposed mode has the simple and reliable operation with few parameters and can efficiently predict the long‐term deformation behavior of rocks subject to multiple wet‐dry cycles.

Tensile strength is one significant parameter involved in tensile fracture in soil mechanics. In this paper, a stress-controlled, uniaxial, direct-tension test apparatus was developed to investigate the tensile properties of soils. A limited number of investigations have examined the impact of anisotropy and loading interval on the tensile strength of undisturbed loess. The deformation and strains generated were also examined during the tests. It was revealed that anisotropy was an important factor affecting tensile strength of undisturbed loess, and the effect of loading interval on tensile strength significantly depended on water content. It was negligible while the water content was below the plastic limit. However, when the water content was above the plastic limit, the loading interval not only affected the tensile strength, but also the failure displacement and stiffness response of the soil. Two patterns of tensile fracture were summarized and discussed. Moreover, an empirical constitutive relation was proposed to describe the stress-strain relationship of undisturbed loess and its robustness was validated by the experimental data.