小行星采矿方案与动力学研究

随着人类对自然资源需求的增加和地球上矿产资源的消耗,向外太空索取资源成为了发展的必然趋势,其中小行星采矿因非常高的经济价值备受关注。近年来,美国冥王号和日本隼鸟2号均实现了对小行星的采样返回,我国天问二号任务也将对小行星进行采样返回。目前小行星采矿方向还停留在概念阶段,为此,本文针对小行星采矿问题,在小行星多面体引力场建模和球面谐波级数表面建模的基础上,对表面开采和掠飞捕获两种小行星采矿方案和所涉及的动力学问题进行研究。针对表面开采问题,提出了一种高效的小行星表面开采方案,并选取小行星Bennu为目标,结合表面开采需求,分析了其表面动力学特性。针对掠飞捕获问题,采用集中质量非线性弹簧阻尼模型仿真模拟了柔性绳网捕获小行星的动力学过程,并分析了部分节点的位移、速度与加速度,为未来小行星采矿任务提供理论指导。

Aspects of surface and environment protection in German mining areas

Hard coal mining in the German Ruhr district has a tradition of more than 200 years. Starting in the south near the river Ruhr with mining of seams near to the surface, mining wandered to the north with coal seams deeper and deeper. In the same way all environmental effects of mining wandered from south to north, as there are abandoned mining sites, contaminated areas, burning mining dumps, subsided areas and gas accesses at day ground. This all happened in a very high populated area with more than four million inhabitants. Therefore Germany has a long tradition in solving environmental problems of mining activities. The very good interaction of mine authority, mining companies and the mine workers’ union is the main reason why the problems of decreasing mining activities in Germany were solved without economic, environmental or social hazards.

Numerical simulation of overburden and surface movements for Wongawilli strip pillar mining

The Wongawilli strip pillar mining technique,which combines the strip pillar mining layout and Wongawilli mining technology,is a new high efficient mining technology for mining under surface structures. The Wongawilli strip pillar mining technique was studied in this paper using theoretical analysis and numerical simulation. As an example,the geological and mining conditions of a coal mine were used to design the Wongawilli strip pillar plans,including the support parameters of the entries and the mining technology. In order to control the surrounding rocks and manage the roof effectively during coal mining,the stress fields,displacement fields and plastic zones were studied by numerical simulation. The stress fields,displacement fields,and plastic zones generated by Wongawilli strip pillar mining were obtained. And the surface movement and deformation were also determined after mining was completed and its effects on surface structures were analyzed and evaluated. The results demonstrate that it is feasible to mine under surface structures with the Wongawilli strip pillar mining technique. This mining method can protect the surface structures from damages.

Preparation and properties of a new cutting pick of coal shearers

Reliability and wear resistance of cutting picks play a significant role in coal mine exploitation with coal shearers.Tool bit separation,blade breaking,severe erosion of the cutting body and fatigue fractures are the main reasons for failure of cutting picks.We carried out carburization on a 30CrMnMo alloy to synthesize a new cutting pick material with improved mechanical properties and high wear resistance.The results indicated that carburization can effectively strengthen the surface of the 30CrMnMo alloy by forming a thick carburized layer and thus significantly improve the surface hardness and wear resistance.In addition,the excellent toughness of 30CrMnMo alloy as a substrate of cutting picks can prevent brittle ruptures and fatigue fractures under high impact stress conditions.The significant decrease in both frictional coefficient and rate of erosion of this carburized 30CrMnMo alloy suggests that this alloy is a potential material for cutting picks of coal shearers after rational carburization.

Unsteady heat-moisture transfer of wet airway in deep mining

To study the mechanism of unsteady heat-moisture transfer of wet surrounding rock in deep mining, a series of experiments with different initial and boundary conditions were carried out. Test results show that rock temperature decreases quickly at the initial stage, and reduces slowly to be a constant value finally for transient heat-moisture transfer. The quasi-steady surface temperature of wet airway is lower than that of dry airway due to the moisture transfer. The diffusion radius is less than the cooling radius owing to the large diffusion resistance. The outlet airflow enthalpy of wet airway is much larger than that of dry airway. Latent heat caused by the moisture transfer plays a significant role in a deep thermal environment. For periodic heat-moisture transfer, temperature, humidity and enthalpy of outlet airflow and rock temperature also change periodically. The wave amplitude of rock temperature decreases gradually with increasing distance away from the airway surface, and the wave phase of rock temperature is also behind that of airflow. Moreover, direction of the heat-moisture transfer between airway and airflow is bidirectional, which is different from results of transient transfer.

德国维特根集团铁路及水利工程施工装备技术交流会在京举行

德国维特根集团是公路、铁路及水利工程施工装备的著名制造商，在全球拥有广大的工程承建商用户，其中，销往中国的压路机、沥青摊铺机等已达数百台。随着中国在铁路、公路及水利工程方面日益增加的建设需要，维特根集团愿意与中国广大的工程承建商携手合作，共同为中国的基础设施建设贡献力量。