Study of energy-efficient heat resistance and cooling technology for high temperature working face with multiple heat sources in deep mine

In the present research,we proposed a scheme to address the issues of severe heat damage,high energy consumption,low cooling system efficiency,and wastage of cold capacity in mines.To elucidate the seasonal variations of environmental temperature through field measurements,we selected a high-temperature working face in a deep mine as our engineering background.To enhance the heat damage control cability of the working face and minimize unnecessary cooling capac-ity loss,we introduced the multi-dimensional heat hazard prevention and control method called"Heat source barrier and cooling equipment".First,we utilize shotcrete and liquid nitrogen injection to eliminate the heat source and implemented pressure equalization ventilation to disrupt the heat transfer path,thereby creating a heat barrier.Second,we establish divi-sional prediction models for airflow temperature based on the variation patterns obtained through numerical simulation.Third,we devise the location and dynamic control strategy for the cooling equipment based on the prediction models.The results of field application show that the heat resistance and cooling linkage method comply with the safety requirement throughout the entire mining cycle while effectively reducing energy consumption.The ambient temperature is maintained below 30℃,resulting in the energy saving of 10%during the high-temperature period and over 50%during the low-temperature period.These findings serve as a valuable reference for managing heat damage in high-temperature working faces.

Comprehensive early warning of rock burst utilizing microseismic multi-parameter indices

Rock bursts have become one of the most severe risks in underground coal mining and its early warning is an important component in the safety management. Microseismic(MS) monitoring is considered potentially as a powerful tool for the early warning of rock burst. In this study, an MS multi-parameter index system was established and the critical values of each index were estimated based on the normalized multi-information warning model of coal-rock dynamic failure. This index system includes bursting strain energy(BSE) index, time-space-magnitude independent information(TSMII) indices and timespace-magnitude compound information(TSMCI) indices. On the basis of this multi-parameter index system, a comprehensive analysis was conducted via introducing the R-value scoring method to calculate the weights of each index. To calibrate the multi-parameter index system and the associated comprehensive analysis, the weights of each index were first confirmed using historical MS data occurred in LW402102 of Hujiahe Coal Mine(China) over a period of four months. This calibrated comprehensive analysis of MS multi-parameter index system was then applied to pre-warn the occurrence of a subsequent rock burst incident in LW 402103. The results demonstrate that this multi-parameter index system combined with the comprehensive analysis are capable of quantitatively pre-warning rock burst risk.

States of Excitons and Linear Optical Spectra in Metallic Single-Walled Carbon Nanotubes

Considering the exciton effect, the excitation energy and its binding energy of the metallic single-walled carbon nanotubes （SWNTs） are theoretically studied by using＂ the simple tight-binding model, based on which the linear absorption spectra are also calculated. It is found that due to the trigonal warping effect, the excitation energies of the linear optical spectra all are split into two corresponding ones. Additionally, the splitting depends on both the chirality and the transition energy： （1） the splitting is maximal for the zigzag tubes, the splitting decreases with the increasing chiral angle; （2） the higher the transition energy is, the larger the splitting is. It is very interesting to find that the obtained results are in good agreement with the experimental results.

密集钻孔弱化坚硬顶板机理的数值模拟及应用研究

煤矿坚硬顶板工作面回采后形成的侧向悬臂梁结构导致邻近工作面回采巷道和煤柱处于高应力状态,使得邻近工作面回采巷道围岩矿压显现剧烈。本文提出了一种密集钻孔诱导形成非连续弱面弱化坚硬顶板的技术方法。根据察哈素煤矿31315工作面的工程地质条件,采用颗粒流数值计算软件PFC^(2D)建立了数值计算模型,研究了密集钻孔周围的应力响应机制和裂缝扩展规律。研究发现,密集钻孔开挖后,钻孔周围岩体因受集中应力而出现渐进性破坏并形成以最小水平主应力方向为长轴,最大水平主应力方向为短轴的椭圆形卸压区。同时,当钻孔直径(D)由30 mm增加到133 mm时,卸压区面积比(λ)从0增加到6.42%,卸压区宽度比(μ)从11.55%增加到54.6%。当钻孔间距(L)从300 mm增加到700 mm时,λ从30.86%减小到9.74%,μ从63.9%减小到33.2%,表明采用较大的直径和较小的间距能够提高密集钻孔对坚硬顶板岩层的弱化程度及卸压效果。现场工业性试验结果表明,密集钻孔诱导形成的非连续弱面有效地弱化了顶板岩层的强度,促进了工作面回采后侧向悬臂结构及时垮落,优化了巷道围岩所处的应力环境,保证了工作面生产安全。本研究为煤矿坚硬顶板的控制方案提供了一种新的技术方法。