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In order to explore the failure characteristics of sandstone under unloading conditions in deep zone with high stress, constant axial pressure and unloading confining pressure tests were conducted on a yellow sandstone sample under different initial confining pressures using the French ROCK600-50 triaxial tester, and the mechanical properties, energy conversion characteristics, and damage evolution law of sandstone failure under unloading conditions were obtained. The test results showed that the axial deformation, the confining pressure for failure, and the shear fracture energy during the failure process of sandstone under the unloading state were positively correlated with the initial confining pressure; the dilatancy amount and speed and the radial deformation were negatively correlated with the initial confining pressure, exhibiting the characteristics of dilatancy under low confining pressure and compression under high confining pressure. Before the unloading point, almost all the energy absorbed by the rock under low initial confining pressure was converted into elastic energy, while part of the energy absorbed under high initial confining pressure was converted into dissipated energy, and the higher the confining pressure, the greater the proportion of the dissipated energy converted. The higher the initial confining pressure, the greater the elastic energy, radial deformation energy, and dissipated energy at the rock fracture point. The larger the unloading confining pressure, the greater the postpeak failure energy and surplus energy of sandstone, and the greater the increase in the proportion of elastic energy converted into surplus energy. The higher the confining pressure, the larger the damage value at the unloading point; the damage speed in the unloading stage was significantly greater than that in the loading stage.

This paper examines the effects of borehole arrangement on the failure process of coal-like materials based on its energy conversion and acoustic characteristics from the perspectives of energy, AE energy, AE spectrum, and frequency band. Findings from the study revealed that the presence of borehole can significantly reduce the conversion ratio and growth rate of elastic energy during the loading of coal-like material sample and delay the release of internal energy of the sample. Also, it can reduce the frequency band energy of the main frequency of acoustic emission signal but has little effect on the size and richness of the peak frequency of acoustic emission signal. The practice that makes drilling diameter and depth increase stepwise can minimize the elastic energy conversion ratio, the growth rate, and the main frequency band energy of acoustic emission signal of coal-like material sample and postpone the internal energy release of the sample to the greatest extent, so as to enrich the richness of the secondary frequency of acoustic emission signal. The results of this study have certain guiding significance for the layout of pressure relief boreholes in the production process of coal mines.

Under the protection of marine water environment, the safety monitoring of anticorrosive coating of port machinery and equipment is non-stationary. In order to improve the accuracy of monitoring and to ensure the safety of anticorrosive coating of port machinery and equipment under the protection of marine water environment, a safety monitoring algorithm for anticorrosive coating of port machinery and equipment under marine water environment protection based on joint estimation of seawater corrosion time and frequency is proposed. In this paper, the corrosion protection information transmission coating model of port machinery and equipment under the protection of marine water environment is constructed, and the association rule characteristic quantity of the safety grade attribute of anticorrosive coating of port machinery equipment under the protection of simulated marine water environment is extracted. The frequency domain equalization method is used to design the anticorrosive and transmission coating for port machinery and equipment under the protection of marine water environment, and the corrosion detection of anticorrosive coating for port machinery and equipment under the protection of marine water environment is carried out in the balanced coating model. The time-frequency parameter joint estimation of corrosion signal of anticorrosion coating for port machinery and equipment under the protection of marine water environment is carried out. According to the result of parameter estimation, the safety grade monitoring of anticorrosion coating of port machinery and equipment under the protection of marine water environment is realized. The simulation results show that the method has good accuracy and strong anti-interference ability in monitoring the safety grade of anticorrosive coating of port machinery and equipment under the protection of marine water environment, and improves the safety grade of anticorrosive coating of port machinery and equipment. [ABSTRACT FROM AUTHOR]