REP10784

• Permit No: M1988112
• IBM Index Class Name: Report
• Doc Date: 7/14/1995
• Doc Name: APPENDIX B.2 CPT PROBES
• Media Type: D
• Archive: No

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CPT-4A 1 75.5 5/ 1/95
CPT-4A2 80.2 5/1/95
CPT-4B 72,5 5/1/95
CPT-4C 57.9 5/1/95
The stnttigraphic interpretation is based on relationships between tip resistance (Qc), sleeve friction
(Fs), and dynamic pore pressure (IJt). The friction ratio, (Ri) (sleeve friction divided by cone
bearing), is a calculated parameter which is used to infer soil behavior type. Differential pore pressure
ratio (excess pore pressure divided by cone bearing) is also calculated. It assists in fine tuning the soil
irrterpretatioa Generally, cohesive soils have high friction ratios, low cone bearing and generate large
excess pore water pressures. Cohesioriless soils have lower fiiction ratios, high cone bearing and
generate little in the way of excess pore water pressures.
The interpretation of the CPT data collected on this project was carried out using the correlations
in Figure 2, developed by Campanella and Robertson, 1988. It should be noted that it is not always
possible to clearly identify a soil type based on Qc, Fs and Ut. Occasionally soils will fall within
differertt soil categories on the classification charts. In these situations, experience and judgement and
an assessment of the pore pressure dissipation data should be used to infer the soil behavior type.
Computer tabulations of the interpreted soil types along with certain other geotechnical pazameters
for each cone hole are presented in Appendix B.
3.2 Pore Pressure Dissipation Data
Two' pore pressure dissipation tests were performed during CPT-4A2. The dissipations were
performed in thin silt lenses which had elevated dynamic pore pressures. The tests were performed
at 64 ft (19.5 m) and 70.5 ft (21.5 m). The test at 64 ft started with a pore pressure of 18.1 psi and
dissipated to 3.4 psi after 10 minutes. The test at 70.5 ft started with a pore pressure of 11.2 psi and
dissipated to 2.4 psi after 5 minutes. Plots of the two tests are in Appendix C.
The dynamic pore pressures from the CPT soundings indicate that the tailings became saturated at
depths of 20 to 30 feet. However, there is no clear hydrostatic water level in tailings. There were
only thin zones with elevated dynamic pore pressure, between sandier zones with little or no dynamic
pore pressure.
3.3 Seismic Data
The pertinent data for each of the seismic profiles are presented in tabular form in Appendix D. The
shear wave velocity profiles for each CPT location can be found in Appendix E. The velocity profiles
display the shear wave velocity plotted at a depth midway between the one meter test intervals. The
measured shear wave velocities were generally between about 400 ft/s and 800 ft/s.
CoNC7EC, INC. 3 Dmvc, Colorado
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