Cross-Hole BALLARD Source
The Ballard Borehole Seismic Source is a tool designed to enable engineering geophysicists and geotechnical engineers to conduct high quality P- and S-wave crosshole tests in accordance with ASTM standards.
Unlike P-wave energy which appears first on a seismic record, S-wave energy must be enhanced to be positively recognized within existing wave trains. This can be best accomplished by a reverse polarity seismic source rich in S-wave energy. Since the polarity of an S-wave can be controlled (unlike the P-wave) the seismic source can provide a positive identification if it is capable of S-wave phase reversal.
The Ballard Borehole Seismic Source is designed to offer S-wave enhancement, S-wave phase reversal, suppressed (but adequate) P-wave energy, light weight, signal repeatability, high frequency (fast rise time), maximum reliability, and low cost. An inflatable sidewall anchor system provides positive borehole clamping. A single three-in-one, 0.5 inch diameter cable houses the controls for reversible spring loaded hammer activation, zero-time geophone and air for the clamping mechanism.
Dimensions : Basic Tool Length – 24 in. Body – Diameter – 2.75 in. Body – Length – 15 in. – Cable – 0.5 in. dia. (length to suit).
Approx. Wt : Basic Tool 2.75 in. dia. – 12 lbs. Cable – 0.25lbs. per foot.
Center Frequency : Approx. 400 Hz.
Trigger : Miniature, 5,000g shock-rated geophone 120 db dynamic range Waterproof (fully encapsulated in stainless steel housing) Bolted to upper anvil.
Sidewall Anchor System : Inflatable double-walled bladder, field replaceable Normal locking pressure, in an air-filled borehole-30 psi. Manual air pump & gauge.
Manufacturer : RT Clark (USA).