Abstract: Apparatus for generating a pressure pulse in a fluid comprising a pipe, an opening into said pipe for filling said pipe with fluid, a piston mounted in the pipe, and coupled to a vibrator output. An air bleeder is mounted through said pipe at a location to remove all the air in the pipe as it is filled with fluid and vibrator control apparatus for controlling the frequency and phase of the vibrator and any additional vibrators coupled to a common fluid path.

Abstract: Method for unplugging a pipeline filled with fluid and solid material by blocking the pipeline below the plugged portion, injecting pressure pulses into the pipeline on both sides of the plugged portion until the plugged portion becomes fluidized and then forcing water into and through the plugged portion to remove the plug. The method further contemplates controlling the frequency and the phase of the injected pressure pulses to best match the length of the pipeline between the injected pulses so that the pulse applied to each side of the plug is out of phase.

Abstract: A method and apparatus for maintaining a second elongated hole axis substantially parallel to a previously bored horizontal hole axis which entails inserting a seismic signal generating apparatus into one hole and a seismic signal receiving apparatus into the other hole. The seismic receiver includes apparatus for moving it along the axis, for maintaining the receiver substantially parallel to the gravitational bottom of the hole, and for moving the receiver a predetermined distance from the borehole wall which is adjacent the borehole containing the seismic signal generating apparatus. Apparatus for observing the detected signal is located outside the borehole.

Abstract: A ground probing radar method and apparatus which is effective to view the earth in advance of coal mining activity provides visual display of a coal seam and particular discontinuities that may lie therein. The system operates in the frequency range of 10 Megahertz to 5 Gigahertz. The received electromagnetic energy is amplified, sampled and band pass filtered with subsequent time gain amplification. A time analog return signal may be viewed directly and/or the return signal may be digitally processed to enable further signal refinement. A control microprocessor is utilized for both tape record control and digital signal processing, and the processor includes the capability for compositing and/or stacking of common source point data for output record and display.

Abstract: A method for boring a hole so that its axis is substantially parallel to the axis of a previously bored hole for positioning an acoustical transmitter and receiver against the hole of the hole being bored so that their position on the wall lies on a horizontal plane through the axis of the bore hole being bored. Then transmitting an acoustical frequency acoustical signal into the wall of the hole. The reflected signal is then received from the adjacent wall along with other unwanted additional reflections. The phase shift is then determined between the transmitted and received signal and the changes in the distance between the wall of the bore hole is then determined.

Abstract: A method for measuring the velocity of earth surface motion utilizing coherent light energy which comprises steps of generating and directing a coherent light beam toward a selected earth surface position, reflecting said beam from a stationary reflector located at the earth surface position, and simultaneously reflecting said beam from a reflector at said earth surface position which moves with earth surface motion; and, detecting the reflected beam, including both the reflection path components, to derive an instantaneous difference frequency that is proportional to the velocity of the earth surface motion.