Coal mining often causes periodic disruption in the rock mass around the stope. The study of the deformation and failure characteristics of cyclic loading and unloading sandstone is very critical for gaining a thorough understanding of the mechanisms of rock damage, degradation, and failure. This kind of investigation is very helpful in determining the precursors of rock failure and the instability of engineering structures. In this research study, the properties of acoustic emission and infrared radiation of cyclic loading and unloading sandstone are explored using a cyclic loading and unloading sandstone experiment. Based on acoustic emission and infrared radiation, the loading–unloading response ratio of rock is established. It is found that the response variables of sandstone during the loading stage based on acoustic emission (AE) counts and the loading–unloading response ratio based on average infrared radiation temperature (AIRT) both rise suddenly in the last cycle, which may be a precursor of “acoustic-thermal” approaching rock failure. On this basis, the quantitative analysis index of infrared radiation of differential infrared energy change rate (DIECR) is proposed, that is, the change of square of ΔAIRT in unit time, and based on AE counts and DIECR, the loading–unloading response ratio of “acoustic-thermal” is defined. It is found that the “acoustic-thermal” loading–unloading response ratio suddenly increases during the penultimate cycle of loading and unloading. This feature can be taken as the initial precursor of rock failure. Together with the “acoustic-thermal” imminent failure precursor of rock, it constitutes the “initial precursor-imminent failure precursor” combined with the internal fracture and surface infrared radiation temperature field during the cyclic loading and unloading process of rock, realizing the hierarchical monitoring and early warning of cyclic loading and unloading rock failure. The research results lay a theoretical and practical foundation for using infrared radiation to monitor engineering disasters caused by rock fracture and failure in mining engineering.

Since rock is heterogeneous, hence its behavior is always variable. The governing parameters in rock deformations are time, applied load, composition, water content, temperature and loading conditions including confinement and loading rate. Time-dependent deformation study is extremely important for the prevention of hazards such as rockburst, roof fall and collapse. In the current study, sandstone samples from Kouzidong Mine China are analyzed using long-term rheological creep tests and advanced microscopic scanning using 3D X-ray microscopy (XRM). Time is the main governing factor in rock rheological creep study. The current study focuses on the microscopic deformation of selected rock using rheological creep and microscopic analysis. Rock behaves differently under different applied loads; therefore, two different loads are applied on two sandstone samples. Two samples are scanned before and after rheological creep testing. The uniaxial constant load applied on the first sample is 40% of the uniaxial compressive strength of the rock (σ1 = 40%σc) for one month. The behavior of the first sample shows an instantaneous creep and stable creep. The maximum uniaxial strain is 0.0307. The scanning results show evidence of microfractures in sandstone sample 1 at a lower load. There is evidence of grain movement and boundary alteration. The grain movement depends on the bonding between different grains. The second sample is loaded at 50% of the uniaxial compressive strength (σ1 = 50%σc). The maximum uniaxial strain for sample 2 is 0.0408. Creep behavior is the same and the microscopic deformation is enhanced with increasing applied load.

Purpose. To analyze the coupling effect between composite slope geometrical parameters. Methods. The slope angle and excavation depth are coupled with load which is waste dump in this case. Several models were created and analyzed to capture their coupling effect and interactions using FLAC/Slope. Findings. When the slope angle and excavation depth are coupled with a load such as that of a waste dump, the factor of safety decreases. But a suitable dumping position can prove vital to enhancing stability. The primary cause of this phenomenon is that the stresses induced by the waste dump decrease as the dump is moved away from the crest of the slope and the stress induced within the zone of active wedge beneath the dump reduces on the reference slip plane. Hence, it can be said that the position of the waste dump in the formation of a composite slope plays a key role in enhancing stability. Factor of safety have the same influence pattern for all parameters induced by stress as that of influence rule. The results obtained from the finite element stress analysis are the same with those obtained for the slope stability analysis. Originality. The current research presents for the first time the coupling effect of the composite slope geometrical parameters and the results of finite element stress analysis, which are similar to those of slope stability analysis. Practical implications. The current research results can be used to effectively analyze and design the composite slopes in soft rocks specially in surface mines.