UBC Theses and Dissertations
Sources and receivers with the seismic cone test Laing, Nancy Louise
Different types of sources and receivers used with the seismic cone penetration test were investigated. The sources investigated were mechanical shear and compression wave sources consisting of a hammer-and-weighted-plank source; an on-shore Buffalo gun source utilizing shotgun shells; an off-shore seismic cap source; and an off-shore embedded blade with seismic cap source. The receivers investigated were horizontal and vertical geophones and accelerometers. The hammer shear source used previously with the seismic cone (Rice, 1984), was used as a standard for comparison. The hammer P-wave source was not used successfully with the seismic cone, because the vertical receivers used in the cone do not represent the soil response and thus can not be used with any source, and because the amplitude of the P-waves produced by the source was not large enough to detect on the horizontal receivers. The Buffalo gun source did not give repeatable or accurate shear wave velocities for depths less than 12 meters, but did appear repeatable and accurate below 12 meters. The seismic cap sources including the embedded blade source were found to give reasonable shear wave velocities and reasonable compression wave velocities if the depth at which the seismic cap was fired was kept constant. Both horizontal geophones and accelerometers were found to give similar shear wave velocities for the hammer shear source, but for the Buffalo gun source the accelerometers give differing results from the geophones probably because of a variable phase shift associated with the filtering of the accelerometer. Vertical receivers were not successfully used with the seismic cone because they do not give a response representative of the soil response, because of the vertical stiffness of the cone and rods. The use of compression and shear wave velocities to determine Poisson' ratio gave reasonable results if the strain level and type of compression wave were taken into account. A preliminary determination of the material damping ratio gave results which were higher than expected, probably indicating the seismic wave receivers were responding to the cone-soil system, rather than to the soil alone.
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