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Rock burst observations from hard rock mines: Failures, successes, lessons learned
Published in Charlie C. Li, Xing Li, Zong-Xian Zhang, Rock Dynamics – Experiments, Theories and Applications, 2018
The local joint dilation (example in Figure 14) created significant difficulties in rehabbing the area affected by the large magnitude events. Not knowing how much support capacity was lost during the seismic episodes, and the fact that the faults involved were not cut off from abutment stresses, the mine attempted to rehab the affected areas. Adding more bolts proved difficult, the dilated jointing offset bolt holes and allowed cartridge resin to flow into the cracks not filling up the bolt holes.
Movement of amphibious rifles fixed on the mount when shooting and operating underwater
Published in Waves in Random and Complex Media, 2022
Hung Nguyen Van, Doan Dao Van, A. M. Zenkour, Phung Van Minh, Do Van Thom
To validate the movement model of the amphibious rifle fixed on the mount when shooting underwater, the 5.56 mm amphibious rifle was used for analysis when firing 5.56 × 45 mm underwater ammo. The MATLAB software is used to solve the above-described problems. The calculation process is performed simultaneously with the solution of the internal ballistic, the thermodynamics in the gas chamber, and the movement of the bolt-carrier when shooting underwater [19]. The input parameters are collected by various methods. The parameters of the geometrical dimensions are determined by building a 3D CAD model. For the dimensions, material parameters are taken from design drawings of 5.56 mm amphibious rifles and 5.56 × 45 mm underwater ammo, while the stiffness of springs and the friction coefficient are determined by experiment on the JY-2 system and UMT system [20]. The calculation is applied to four cases of different water environment pressure, corresponding to shot depths of 0.05 , 5 , 10 , and 20 m. The main inputs for calculations are shown in Table 1.
Experimental study on impact damage of membrane-type LNG carrier cargo containment system due to dropped objects
Published in Ships and Offshore Structures, 2018
It is hard to drop an object onto a specific location from a height of 27 m. Thus a gun-type impact test machine was devised and used. This machine could deliver the impact velocity and adjust the impact location according to the impact scenarios in Table 5. Figure 10 shows the schematic of the gun-type impact test machine. A dropped object, for example a bolt and nut assembly, was put inside a barrel pipe and launched by compressed air from the air chamber by opening Valve 2. The impact velocity delivered by the impact test machine can be determined by the level of compressed air pressure in the air chamber. The air chamber was pressurised with the air compressor. After the air chamber was pressurised about 10% more than the desired pressure, the air compressor was disconnected from the air inlet, and by opening and closing Valve 1 the desired pressure was obtained. The impact location could be adjusted by adjusting the longitudinal direction of the barrel pipe, as the target structure was fixed vertically on the rigid wall in front of the barrel pipe. By moving the frame of the impact test machine from side to side and adjusting the column height, the impact location could be set to match the impact scenarios, as shown in Figure 11(a). Two barrel pipes of different internal diameter were prepared, and could be changed according to the size of the object, i.e. a barrel pipe with 35 mm internal diameter was prepared for the bolt and nut assembly and another barrel pipe with 100 mm internal diameter was prepared for the pipe support, as shown in Figure 11(b,c).
Instability Mechanism and Engineering Cases of the Surrounding Rock in Deep High Stress, Weak Strata Chambers
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Sijiang Wei, Peicheng Gao, Chongyang Wang, Sheng Zhang, Meng Wang
From January 2007, according to the deformation and failure of the chamber, the section was enlarged compared to the original support, and the high-strength bolt and anchor cable were used for combined support. The roof and walls of the chamber were strengthened by bolt-cable coordination. The floor failure zone was excavated. Then, concrete was used to strengthen the floor.