Wave propagation effects from blast induced vibrations

Övrigt konferensbidrag, 2020

Blasting in rock may cause structural damages to nearby buildings. In order to minimize the risk for such damages, restrictions are imposed on the speed of rock excavation, e.g. on the choice of method or on charging levels. There is a wide variation among different countries regarding standards and legislations with respect to blast induced vibrations [1]. Criticism has been raised against this confused situation, for example concerning this non-uniformity within EU or among states in the US. Moreover, as regulations by their nature are conservative limits, tolerable vibration levels are often considered too restricted [2]. It is thus of importance to continue develop more reliable predictions on ground and structural vibrations from blasting in rock, as this enables a more efficient rock excavation process that may lead to both economic and environmental savings.
The aim of this work is to study some effects from the most important differences among the blasting regulations in European countries. This covers phenomena from different vibrational regions, such as ground and surface wave propagation effects and above-ground structure responses. There are of course many parameters that are of importance, where only a few will be covered here. Of particular interest is to study various sorts of frequency based norms, used in most European countries, in comparison to norms based on distance and overburden, used in Nordic countries [3]. Moreover the set of peak particle velocity (PPV) data that are used varies among the countries (vertical, horizontal, resultant), as well as sensor monitoring positions [1]. These PPV directions relate to the wave content (compressional, shear and Rayleigh waves) and each component/wave affects the structural response differently.
To this end numerical results are presented using 2D FEM. Structural responses are calculated on different detail levels; using response spectra (SDOF), simple MDOF structures as well as continuum theories for schematic buildings. These results are compared to results presented in the literature. The goal is to develop better understanding how the strain picture in a set of buildings couple to some of the aforementioned important parameters (PPV levels and directions, frequency content, wave types) for a few different blasting situations (varying charging level and location as well as underground material parameters rock/soil)[4].