Vibration
Geotec offers various measurement services of ground vibrations and air blast, caused by blasts, heavy duty construction equipment and other sources. The purpose of the measurements is to prevent damage to structures and discomfort to people. Additionally, vibration measurements enable contractors to plan their activities on the basis of accurate scientific information and maximize the efficiency of their work under given conditions.
- Measurement of the air blast caused by the detonation of charges
- Measurement of ground vibrations caused by blasts
- Measurement of ground vibrations caused by transportation and heavy duty construction equipment
- Determination of the “Site Law” (Scaling Law) for blasts, heavy duty construction equipment, transportation, piles driving, dynamic compaction, etc.
- Maximal vibrations level as a function of the distance and the released energy
- Calculation of the maximal charge per delay as a function of the distance for a given vibration level
- Calculation of the safe operating distances of heavy duty construction equipment
- Calculation of the "Site Law" for air blast
During a blast, or when operating heavy construction equipment, energy is released. This energy is dispersed in all directions; some of it, in the form of seismic waves (elastic waves). The propagation velocity of the seismic waves ranges from hundreds of meters per second in the ground to thousands of meters per second in rocks. Seismic waves disperse in a spherical manner in all directions, where the center of the sphere is the point of energy excitation at the energy source.
As the seismic waves propagate, they cause vibrations that are measured in four ways: frequency, displacement, velocity and acceleration. In order to determine risk level to structures, one usually refers to the particle velocity of the vibration that is created at the structure`s foundations or on the ground, near its base. The order of magnitude of this velocity is millimeters per second to centimeters per second.
Apart from the level of energy produced by the energy source, the ground properties significantly influence the level of potential damage to a structure. Vibration measurement involves the positioning of seismographs, including a sensor called a "geophone". Geophones are tri-axial sensors; i.e., they are sensitive to vibrations in three directions in an orthogonal coordinates system.