Application of AHP-GRA in safety evaluation of blasting flying stones

Blasting flying stone is one of the six hazards in rock and soil blasting construction. In order to determine the risk level of blasting flying stone, 3 first-grade indexes such as blasting design and construction are selected, and 11 second-grade indexes such as warning range are not set, so as to establish the blasting flying stone safety evaluation model of AHP-GRA. The analytic hierarchy process (AHP) was used to calculate the weight of the evaluation index. The grey correlation method was used to determine the correlation degree between the blasting flying stone and the safety level of an airport. The risk level of an airport was calculated based on the weight of the evaluation index, and the engineering verification was carried out. The results show that there is no warning signal, no notice before detonation and the warning range is too small, which are the main factors of the flying stone accident. The model presented in this paper is used to evaluate the blasting flying stones in an airport, and the evaluation results are basically consistent with the reality. It can be seen that the evaluation model can scientifically and reasonably evaluate the risk level of blasting flying stones, which has important practical significance.

Risk assessment of Ordovician limestone water inrush in No.9 coal seam of Yangdong coal mine and its prevention and control measures

With the increasing of mining depth, intensity, scale and speed, Ordovician limestone water has become the biggest threat to the safety production of the low group seam. Based on the existing geological data, the hydrogeological characteristics of Ordovician limestone water are analyzed; the risk of Ordovician limestone water inrush is evaluated by using the method of “five maps and double coefficients” and considering the importance of effective protective thickness of floor protective layer in the evaluation results. The results show that there are no non straight through relative safety area (Area I) and non straight type relative risk area (Area II), only non straight type water inrush risk area (Area III) and straight through water inrush risk area (Area IV). According to the evaluation results, the floor grouting reinforcement is directly adopted in Area IV, and the Ordovician limestone may need to be modified in the strong water rich area; in Area III, the grouting transformation of the floor is carried out after the area with water inrush is identified first, but the Ordovician limestone is not needed. Other prevention and control measures should be subsidiary.

Gravity defined precisely with quarks – squaring the circle to achieve fine description of black hole physics, and understanding the formation of key constellations

Gravity is redefined by drawing on the author’s works and inputting quark physics in a way consistent with it ; it allows to better understand black hole dynamics, black hole eruptions and some constellation patterns in the sky (the Scorpio, Ursa Minor and Ursa Major as well as Cassiopea for instance). The concept of gravitational lensing is rapidly differenciated from black hole eruptions. Some final remarks underline a possible threat for missions to the Moon.