THE USE OF A COUPLER IN THE CONVERSION OF IMPACT ENERGY INTO SEISMIC ENERGY

Abstract

The factors which influence the efficiency of generation of seismic energy by a falling weight‐coupler system have been investigated both theoretically and experimentally using model techniques. Two media, sand and clay‐silt‐sand, were used. Source conditions were changed by (1) varying the mass of the falling weight, (2) varying the drop‐height, and (3) embedding various bodies (couplers) at the impact point. The results showed that for compressional waves: 1. [Formula: see text] where A is the amplitude of the seismic signal, M the mass of the coupler, and [Formula: see text] the maximum speed of the coupler. 2. The seismic energy is not proportional to the source energy. 3. In general, for a given source energy the larger the falling mass the more efficient is the generation of seismic energy. 4. The coefficient of restitution between the falling mass and coupler can be determined from seismic‐wave amplitudes. 5. Complex waves can be generated when the mass of the falling weight is greater than that of the product of the mass of the coupler and the coefficient of restitution. 6. The wave shape depends on the coupler mass and the elastic properties, and the degree of compaction of the medium. 7. The stacking of suitable masses on the coupler can increase the seismic efficiency by a factor of nearly four. The results of this study have important implications in the practical application of the weight‐drop method used in seismic exploration and in other related energy coupling studies.