tailieunhanh - Vibration Control Part 16

Tham khảo tài liệu 'vibration control part 16', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 364 Vibration Control Particle Velocity Damage in sec in sec in sec in sec No damage Plaster cracking Minor damage Major damage to structures Table 4. USBM 1971 . Type of structure Type of damage Particle velocity at which damage starts Rigidity mounted mercury switches Trip out in sec Houses Plaster cracking 2 in sec Concrete blocks in a new home Cracks in block 8 in sec Cased drill holes Horizontal offset 15 in sec Mechanical equipment pumps compressors Shafts misaligned 40 in sec Prefabricated metal building on concrete pads Cracked pads building twisted and distorted 60 in sec Table 5. Equipment and Structure Damage Criteria Canmet Bauer and Calder 1977 . Method 1- Limiting particle velocity criterion requires that each blast be monitored by a seismograph capable of monitoring peak particle velocity. Providing the maximum particle velocity stays below the levels specified in table 6 . Method 2- Scaled distance equation criterion requires the operator to design shots in accordance with table 6 which specifies a scaled distance design factor for use at various distances between a dwelling and blast site. No seismic recording is necessary. Providing that scaled distance in table 6 is observed. Method 3- Blast level chart criterion This method allows an operator to use particle velocity limits that vary with frequency as illustrated in Figure 6. This method requires frequency analysis of the blast-generated ground vibration wave as well as particle velocity measurements for each blast. This method may represent the best means evaluating potential damage to residential structures as well as human annoyance from blasting. Any seismic recordings for any component longitudinal transverse or vertical for the particle velocity at a particular predominant frequency that fall below any part of the solid line graph in Figure 6 are considered safe. And any values that fall above any part of the solid line graph will increase the likelihood of .