Spatial Modeling of Tsunami Vortices in the Coastal Ocean

It is important to plan for potential tsunamis during the marine spatial planning process so that land uses may be modified or defensive infrastructure may be erected. Tsunami vortices had been observed during the occurrence and propagation of tsunami waves. Actual observations during the March 2011 Japan tsunami and the Indian Ocean tsunami of December 2004 showed the formation of vortices which lasted for several hours. The Palu tsunami of September 2018 in Indonesia also showed the formation of a tsunami vortex whose centre was photographed by a pilot and appeared as a deep hole in the ocean. Several vortices with various sizes lasted for several hours after the quake and they also generated a loud roar as the giant waves inundated low-lying coastal areas. This essay attempts to describe the development of a model that can explain the formation of tsunami vortices.

FINITE ELEMENT ANALYSIS OF TOOLS FOR DEEP DRILLING TECHNOLOGY

Using the ANSYS software package, the issues of strength of the drill head and temperature distribution were considered, the design of a modern tool for deep hole drilling was analyzed, and modal analysis was carried out to exclude possible resonance phenomena.

Optimization and Practice for Partition Pressure Relief of Deep Mining Roadway Using Empty-Hole and Deep-Hole Blasting to Weaken Coal

Rockbursts are among the most harmful dynamic disasters, threatening the personnel safety and mine operation. In order to alleviate stress concentration of roadsides and prevent rockbursts, the large-diameter boreholes and deep-hole blasting are employed for partition pressure relief in the deep mining roadway. Combined with failure behavior and stress distribution of the coal, the multilevel division of risk degree for roadsides stress is determined. Based on the orthogonal test of borehole pressure relief in the general danger partition, the response degree of quantitative indexes to main factors influencing the pressure relief effect is considered. The optimal drilling parameters of 120.0 mm diameter, 20.0 m depth, 1.0 m hole spacing, and 5° elevation angle are obtained, determining the stress boundary of safe pressure relief with boreholes. At higher dangerous stress divisions, the optimized blasting parameters through numerical simulation could be obtained as follows: 15.0 m depth, 1.3 decoupling coefficient, and 2.0 m hole spacing, and meanwhile, a stress relief partition of crisscross cracks with 0.61 m height is formed. The roadsides stress could be well controlled within the safe level. Then, an optimal combination of pressure relief is applied to different stress partition of roadsides, and the effectiveness is validated by field test, which proves remarkably applicable for engineering.

Experimental Study of Gangue Layer Weakening with Deep-Hole Presplitting Blasting

Advances in coal mining technology and an increase in coal output are resulting in increasingly challenging conditions being encountered at coal seams. This is particularly so at thin coal seams, where a large number of hard rock layers known as gangue are often present, which seriously affect the normal operation of the shearer and reduce coal output. Therefore, the effective weakening of hard gangue layers in a coal seam is crucial to ensure that the shearer operates effectively and that coal output is maximized. In this paper, the weakening effect of deep-hole presplitting blasting technology on the hard gangue layer in a coal seam is studied via a similar simulation. Four test schemes are designed: (1) A blasting hole spacing of 200 mm with the holes offset vertically. (2) A blast hole spacing of 300 mm with the holes offset vertically. (3) A blast hole spacing of 200 mm with the holes parallel to the gangue layer. (4) A blasting hole spacing of 200 mm with the holes offset vertically and initiation of interval blasting. The effect of the different blasting hole spacings and arrangements and different detonation methods on the weakening of coal seam clamping by gangue is studied, and the best configuration is identified. This improves the effect of weakening the coal gangue layer by deep-hole presplitting blasting.

Analysis and Test of Conductive Shaft of Large Horizontal NC ECM Machine Tool

In order to solve the problems of serious heating and easy ablation of conductive shaft in electrochemical machining of special-shaped deep hole with large aspect ratio, the two schemes of single side copper bar and symmetrical copper bar of conductive shaft were studied by ANSYS software. And the conductive shaft scheme based on symmetrical copper bar scheme was determined. The thermoelectric coupling model of the conductive shaft was established to analyze the distribution law of temperature field and thermal deformation of conductive shaft under different working conditions. Through the machining test of special-shaped inner spiral deep hole parts with large aspect ratio, the results show that under the conditions of working current of 15 000 A, feed rate of 5 mm/min and continuous machining for 14 hours, the forming accuracy of the workpiece is ±0.15 mm and the surface roughness is better than Ra0.8 µm. The performance of the conductive shaft is stable and meets the actual processing requirements. The heat dissipation performance of the conductive shaft can be optimized by providing air flow on the upper surface and side at the same time.