This technique is based on the recording of ground movement on the surface produced by anthropogenic sources, such as blasting, traffic, sheet pile driving, etc. The vibrations produced by these sources are characterized by their high amplitude and high frequency content. These characteristics mean that the vibrations cannot be recorded with conventional seismometers and, therefore, specific instrumentation is required.

Methodology

The ground movement records are analyzed to check whether the peak and frequency of the seismic vibrations produced by blasting, traffic, etc. meet the threshold that has been established for the study area. The regulation that is commonly used is UNE 22.381. This regulation defines three different thresholds depending on the construction type and use of the building affected by the vibrations: industrial buildings, residential buildings and structures of architectural value.

Example of measurement and control of vibrations produced by a blasting operation.
Left: time record of the three components of the ground movement (blue: longitudinal, green: vertical, red: transverse).
Right: comparison between the speed peaks and the UNE 22381 prevention criterion.

Vibration measurement equipment installed during blasting control.

Applications

The applications of vibration measurement are basically extended to the fields of civil engineering and mining, but they can also be used in the field of the environment. The ICGC uses this technique in mining, to control vibrations produced by blasting (quarries and public works such as tunnels). This technique has also been used in urban areas to control vibrations produced by traffic, metro, railway, etc.

An example of an application is the work carried out to evaluate the effects of vibrations produced by blasting on the surface of a slope or embankment applying the Newmark method (1965), a theory developed for the study of earthquakes as triggers for landslides. The Geophysical Prospecting Unit of the ICGC establishes a new methodology with very satisfactory results where criteria are described based on which the blocks of the slope or slope receive damage, since they are affected by the displacements induced by the pulsation. In addition, the Newmark method takes into account the damage that accumulates in the blocks due to successive blasting. This damage can be quantified, thus providing a zoning of the risk of landslides in the study area that allows identifying critical points where the probability of the slope being affected increases.

References

Newmark, N. M. (1965). “Effects of Earthquake on Dams and Embankments”. Geotechnique, Vol. 15 (2): 139-159.