Variation of shear wave energy with coupling stress in the SCPT method

摘要

The modern downhole seismic cone penetration test (SCPT), which has been integrated into the standard cone penetration test (CPT), is used in geotechnical engineering studies to determine shear wave velocity and dynamic modulus profiles in soils. Although recommended test procedures exist for the SCPT method, no standard specification is available for the seismic source. Tests have been performed on four types of steel beams to investigate the effects of shape, stiffness and coupling stress on horizontal shear (SH) wave energy. The beams were weighted down by weights, which were coupled to the beams to produce various soil-beam-coupling stresses. The results confirm an increase in SH signal energy with increasing coupling stress as previously known. However, the maximum signal amplitude is reached at relatively low coupling stresses between 10 kN/m~2 and 30 kN/m~2, irrespective of size and type of source, for similar hammer impact energy. One of the sources constructed with anchor blades to improve soil interaction performed better than the others that had smooth coupling surfaces.