Presented are the results of measuring variations of water level in an observation well during a ripple-fired explosion in a mine.
Measurements were held in a well at the territory of one of the mining enterprises in the Belgorod district, Russia. The well is 141m deep. It penetrates to the Archean- Proterozoic complex of complicatedly dislocated rock, in which mining operations take place.
The water level at the moment when the measurements started was 83.41m from the free surface. The measurements were held with sensors of two types - a sensor of water level and a 3-component seismometer, which was installed at the surface near the well head. An explosion at the mine was chosen for measurements, when one of the chambers was located extremely close to the observation well. The distance from the water level sensor, which was sunk into the well to the depth of 85.5m, to the ceiling of the chamber, in which about 10 tons of explosive was blasted, was only about 240m.
The results of measurements showed that the maximal amplitude of dynamic oscillations of water level was 12mm. The main frequency of oscillations was in the range of 15-20Hz, which coincided with the frequency of the signal recorded by the seismometer. No residual changes of the water level accompanying the passage of seismic waves produced by the explosion were observed.
Observations over variations of underground water level in wells had started long ago. They are used for various purposes. Bredehoeft (1967) dates first publications concerning the effect of Earth tides on variations of underground water level to 1880. In the abovementioned paper as well as in the papers by Hsieh et al. (1987; 1988) the characteristics of water level variations in an open well under cyclic loads, such as Earth tides and atmospheric pressure, had been obtained analytically. Cooper et al. (1965) and Liu et al. (1989) had obtained an analytical solution for oscillations of water level in an open well under the action of seismic waves.