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R <br /> I <br /> r� <br /> 3.0 CPT DATA INTERPRETATION <br /> i� Inte retation of cone <br /> rp penetration test (CPT) data can yield inflarrradan on site <br /> stratigraphy, hydrogeology, and geotechnical pe-rameters. The following sections briefly <br /> describe data interpretation methodolagi3s for each of these three general data <br /> categories. More detailed Information on this subject is available from the references <br /> cited in the text throughout this section. <br /> - 3.1 S T RA nGRAPHY <br /> i <br /> _ The most common method of obtaining CPT-derived stratigraphic Information is by means of <br /> established correlations between soil type and the measured cone tip and sleeve friction <br /> resistances. The soil stratigraphy interpretations, if provided for this project, were <br /> conducted using the correlation iliustrated in Figure 3. The sleeve friction value is <br /> normalized with respect to the conn tip resistance to create the "friction ratio" <br /> parameter, which expresses the sleeve friction as a percentage of the measured cone tip <br /> resistance. The cone tip resistance measurement is overburden-normalized to an effective <br /> overburden pressure of 1 ton/ft2, as follows: <br /> qct = ac CN (3) <br /> Where qct = overburden-normalized cone tip resistance in tons/ftz, <br /> r» qc = measured cone tip resistance in tons/ft2, <br /> CN = 1 -log av' (minimum value of 0.4),and <br /> av' = effective vertical overburden stress in tons/ft2. <br /> The CPT-sail type correlation shown in Figure 3 was developed through comparison of c <br /> side-by-side CPT and conventional borehole sample laboratory tests, and is based on Earth <br /> Technology's experience thrc ghout much of the Western United States, <br /> These correlations have proved to be applicable to most natural soil deposits. When <br /> applied to a given natural site, the level of uncertainty in the soil type predictions is <br /> often limited to the range of soil classification occupying each band of the correlation <br /> chart. If necessary. CPT-derived soil type information can be verified by conducting a ` <br /> single CPT adjacent to a conventionally logged borehole, thereby creating a site-specific <br /> correlation which can then be extrapolated to all of the remaining CPT locations on the ! <br /> i site. i <br /> 9 <br /> - i <br /> x <br />