The loading modes and roof lithology have a significant influence on the mechanical properties of coal seams. To reveal the failure modes and energy evolution law of underground coal during the mining process, conventional uniaxial and uniaxial cyclic loading tests were carried out on three types of samples: coal, rock, and coal-rock combinations. The results show that the samples mainly behave with three failure modes (shear slip, tensile splitting, and fracture), and all the coal sections in the coal-rock combinations fail, whereas most rock sections remain intact. The compressive strength of the coal-rock combination is higher than coal and much smaller than rock. Compared with the conventional uniaxial loading condition, both the maximum deformation before failure and Young’s modulus under the cyclic loading condition are greater, and the latter increases quadratically with the cycle index. The energy densities are also calculated, and their variations are analysed in detail. The results show that with increasing cycle index, both the elastic energy stored in the sample and the dissipated energy increase in a quadratic function, and the failure process becomes more intense. This research reveals the failure modes, deformation characteristics, and energy evolution of the coal-rock combination under different loading conditions, which can provide strong support for controlling underground surrounding rocks of the coal face and roadway in coalmines.

Layered rocks exhibit notable transverse isotropy and have a significant impact on the deformation and failure characteristics of underground structures. To a large extent, the mechanical properties of layered rocks are related to the structure and stress state of their bedding planes. To obtain an in‐depth understanding of the deformation and yield characteristics of layered rocks, a mechanical model for layered rocks incorporating planes of weakness and volumetric stress is proposed by improving the strain‐hardening/softening ubiquitous‐joint model based on continuum mechanics methods. In this mechanical model, elastoplastic equations for the matrix and bedding planes of layered rocks are established. The evolution of the mechanical parameters of the matrix and bedding planes of layered rocks with the internal variable is determined. In addition, the sensitivity of the model parameters is analyzed, and a method for determining the parameters is provided to reduce the complexity in obtaining these parameters. The numerical calculation results for the laboratory tests on layered sandstone specimens under various stress levels agree relatively well with the test results, thereby validating the effectiveness of the improved model. The methods and results of this study provide a significant reference for the analysis of the deformation and failure of other layered rocks.

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Based on the foreboding information monitoring of the energy released in the developing process of rock burst, prediction system for rock burst can be established. By using microseismic method, electromagnetic radiation method, and drilling bits method, rock burst in Yangcheng Mine was monitored, and a system of multi-index monitoring and evaluation on rock burst was established. Microseismic monitoring and electromagnetic radiation monitoring were early warning method, and drilling bits monitoring was burst region identification method. There were three identifying indexes: silence period in microseismic monitoring, rising period of the intensity, and rising period of pulse count in electromagnetic radiation monitoring. If there is identified burst risk in the workface, drilling bits method was used to ascertain the burst region, and then pressure releasing methods were carried out to eliminate the disaster.

Conducting polymer hydrogels are widely used as strain sensors in light of their distinct skin‐like softness, strain sensitivity, and environmental adaptiveness in the fields of wearable devices, soft robots, and human‐machine interface. However, the mechanical and electrical properties of existing conducting polymer hydrogels, especially fatigue‐resistance and sensing robustness during long‐term application, are unsatisfactory, which severely hamper their practical utilities. Herein, a strategy to fabricate conducting polymer hydrogels with anisotropic structures and mechanics is presented through a combined freeze‐casting and salting‐out process. The as‐fabricated conducting polymer hydrogels exhibit high fatigue threshold (>300 J m−2), low Young's modulus (≈100 kPa), as well as long‐term strain sensing robustness (over 10 000 cycles). Such superior performance enables their application as strain sensors to monitor the real‐time movement of underwater robotics. The design and fabrication strategy for conducting polymer hydrogels reported in this study may open up an enticing avenue for functional soft materials in soft electronics and robotics.