dgillette
Geotechnical
- May 5, 2005
- 1,027
I'm dealing with an old (~100 years) hydraulic fill dam in a seismically active area. Among my difficulties is interpreting SPTs with very low recovery (mostly 30-50 percent, some much lower and almost none above 70 percent). The low recovery is concerning because the fines and PIs in the recovered material suggest that the stuff might not be so bad in medium-size earthquakes, but I'm not convinced that the recovered material is representative. Seems to me that the clayiest stuff is the least likely to be lost out of the sampler. Unfortunately, the data are all "past tense," with no potential to get more or to talk with the drillers. Not completely sure about drilling methods. They were done with hollow-stem augers, and I THINK the hole was advanced ahead of the augers with a rotary bit and clear water. I don't know how careful they were about keeping the augers full, not tripping out too quickly, etc. Pretty sure they did not use catchers in the sampler. The raw blow counts, N, are generally very low (many in single digits at depths over 50 feet).
I have a few CPTs, but none the full depth of the hydraulic fill. qc is quite low in much of the embankment. However, Ic is very high there, mostly 2.5 - 3.5 (implying that it's clayey), but if the layering is thin, Ic might not mean a whole lot. The qc trace suggests layering with thickness 1/2 to 1 foot thick.
Have any experience with SPTs or CPTs in hydraulic fill?
I have very limited information about the construction practices, but that's a different headache.
Cheers!
DRG
I have a few CPTs, but none the full depth of the hydraulic fill. qc is quite low in much of the embankment. However, Ic is very high there, mostly 2.5 - 3.5 (implying that it's clayey), but if the layering is thin, Ic might not mean a whole lot. The qc trace suggests layering with thickness 1/2 to 1 foot thick.
Have any experience with SPTs or CPTs in hydraulic fill?
I have very limited information about the construction practices, but that's a different headache.
Cheers!
DRG