Diagnosis of utility pipelines' response to explosives using modal analysis

摘要

In recent years, the use of modal analysis has increased in include many different aspects of the construction industry. Computer modal analysis can be used in determining the dynamic properties of a structure by mathematical equations and knowledge of the structure's physical propertis. This technique can now be used to predict the level of vibration induced by blasting on adjacent structures. Ground vibration induced by buried explosives is a major concern for contractors when excavating near utility pipeliknes such as gas and water lines. The size limitations placed on easements causes the necessity of additional utilizity lines to be placed in close proximity to existing lines. Through the development of computer models of the pipe, stress analysis can be performed prior to blasting. Baed on the calculated dynamic properties (natural frequencies and modal shapes) and the maximum allowable displacements and stress levels (which are established by the pipe manufacturer) the allowable maximum charge weight per delay can be selected for the blast. The selected mximum charge weight per delay will ensure that the resulting pipe peak particle velocity level is within 95