| 摘要 |
A seismic source for crosshole testing comprises a hammer rod supported by axial bearings in the ends of a cylindrical housing. Fasteners attach a down-blow hammer to the hammer rod inside the housing. A helical spring inside the housing biases the hammer rod in a downward direction. A hammer cable, attached to the upper end of the hammer rod, raises the hammer rod against gravity and spring pressure until an up-blow hammer attached to the hammer rod below the cylindrical housing strikes the bottom end cap which serves as an anvil. Relaxation of the hammer cable tension results in the down-blow hammer striking the anvil. The device provides compression waves and highly repeatable and selectable-phase shear waves. The device is simple, light and operable by a single person.
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