Bulletin of the Geological Society of Malaysia, Volume 40, July 1997, pp. 71 – 76
1Jabatan Geologi, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor
2Jabatan Kejuruteraan Awam dan Struktur, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor
Abstract: A seismic shear wave refraction survey was carried out to examine subsurface profile of the shear wave velocities. The information of the shear wave velocities were required to investigate the dynamic shear wave characteristic of the ground for foundation design of a vibrating machine. A 24-channel Abem Mark III signal enhancement seismograph and shear wave geophones were used in the survey. The field setup for the survey was similar to the conventional P-wave seismic refraction with close geophone spacing of 1 metre. The seismic source was a weighted timber plank spike to the ground and hammered from opposite direction in order to record two sets of traces having opposite shear wave polarity. A computer programme was used to analyse the reverse polarity records and pick the first shear wave arrival times.
A maximum of three layers were recognised from all the spread lines interpreted. The result shows that with the exception of seismic line 1, the range of shear wave velocity for the first layer was found to be in the range of 102 to 379 m/s. Second layer velocity ranges from 182 to 556 m/s and the third layer was found to be in the range of 330 to 774 m/s. The result indicates that the shear wave velocity of the layers are high and this can be attributed to the presence of a fill material (crusher run) that was common for most of the profiles except for spread lines 2, 7 and 8. The range of shear wave velocity layers for these three spreads were as follows:
Layer Velocity (mls) Thickness (m)
1 114-255 0.1 to 5.9
2 186-281 0.4 to 6.9
The shear wave velocities for these spread lines appear to be low and correlate well with SPT values from adjacent bore holes and agreed well to empirical correlations established by previous researchers. These velocity values were therefore recommended to be adopted for design purposes of the foundation and could be used to determine the critical soil deformation below the proposed vibrating machine in the study area.