Explosively-induced ground vibration in civil engineering construction
Research has been undertaken to improve techniques used in the prediction of ground vibration caused by civil engineering construction works. In particular, the effects of explosive excavation of rock for subsurface structures is considered. Factors affecting the input and propagation of explosive energy in the rock mass are investigated, and recommendations made on procedures for trial blasting and the most effective data processing and presentation for the derived predictive equations. These developments are supported by blasting trials at two major road construction sites, where vibration measurements were taken during conventional and innovative blasting operations. A critical review of contemporary dynamic structural damage and intrusion criteria is provided. It is concluded that vibration prediction and control techniques, together with workable damage/intrusion criteria, can be applied which substantially mitigate vibration hazard. The distribution of vibration associated risk between employer and contractor is discussed and contractual options presented. Techniques to determine the engineering properties of rock masses by analysis of stress waves from explosive and hammer impact sources have been developed and successfully tested. The advantages and limitations of the most promising seismic methods are discussed and field seismic classifications are compared with known rock mass properties and established geotechnical classification systems. The research shows that both rock mass properties and 'site specific' laws of vibration decay may be obtained during the trial blasting sequence of a site investigation programme.