Experimental study on the interrelation of multiple mechanical parameters in overburden rock caving process during coal mining in longwall panel

In order to comprehend the dynamic disaster mechanism induced by overburden rock caving during the advancement of a coal mining face, a physical simulation model is constructed basing on the geological condition of the 21221 mining face at Qianqiu coal mine in Henan Province, China. This study established, a comprehensive monitoring system to investigate the interrelations and evolutionary characteristics among multiple mechanical parameters, including mining-induced stress, displacement, temperature, and acoustic emission events during overburden rock caving. It is suggested that, despite the uniformity of the overburden rock caving interval, the main characteristic of overburden rock lies in its uneven caving strength. The mining-induced stress exhibits a reasonable interrelation with the displacement, temperature, and acoustic emission events of the rock strata. With the advancement of the coal seam, the mining-induced stress undergoes four successive stages: gentle stability, gradual accumulation, high-level mutation, and a return to stability. The variations in other mechanical parameters does not synchronize with the signifcant changes in mining-induced stress. Before the collapse of overburden rock occurs, rock strata temperature increment decreases and the acoustic emission ringing counts surges with the increase of rock strata displacement and mining-induced stress. Therefore, the collaborative characteristics of mining-induced stress, displacement, temperature, and acoustic emission ringing counts can be identifed as the precursor information or overburden rock caving. These results are in good consistent with on-site situation in the coal mine.

New approach for the digital reconstruction of complex mine faults and its application in mining

Visualization of complex geological structures can technically support the accurate prediction and prevention of coal mine disasters.This study proposed a new digital reconstruction method to visualize geological structures based on establishing a virtual model in the digital twin system.This methodology for the digital reconstruction of complex fault structures comprises the following four aspects:(1)collection and fdelity of multi-physical feld data of the fault structures,(2)the transmission of multi-physical feld data,(3)the normalization of multi-physical feld data,and(4)digital model reconstruction of fault structures.The key scientifc issues of this methodology to be resolved include in situ fdelity of multi-feld data and normalized programming of multi-source data.In addition,according to the geological background and conditions in Da’anshan coal mine in western Beijing,China,a preliminary attempt is made to reconstruct a digital model of fault and fold structures using the methodology proposed in this study.

Optimized design and experiment of the three-arm transplanting mechanism for rice potted seedlings

The transplanting arm of two-arm transplanting mechanism is easy to cause seedlings injury and missing due to its faster speed relative to the seedlings.In order to solve the existed problems,a three-arm transplanting mechanism for rice potted seedlings was developed in this study.The developed three-arm transplanting mechanism for rice potted seedling can make the transplanting arm realize special trajectory and attitude through the unequal planetary gear transmission.The kinematic model of three-arm transplanting mechanism for rice potted seedling was established,and the optimal design software was developed.Based on the heuristic optimization algorithm named“parameter guide”,a set of satisfied mechanism parameters required by the rice potted seedling transplanting were obtained.The trajectory and attitude of three-arm transplanting mechanism used for the rice potted seedling were analyzed.Besides,the virtual simulation results were basically consistent with the optimization software results,and the correctness of theoretical analysis and virtual simulation were also verified by each other.When the developed transplanting mechanism picked up the seedling,the velocity of transplanting arm relative to the seedling was reduced by about 30%.The results showed that the injury rate of rice potted seedling transplanting mechanism was 0.04%,the missing rate of seedling was 1.4%,the integrity rate of seedling pot matrix was 96%,and the success rate of picking seedling was 99.92%.