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i � u <br /> EAG Gregg In Situ <br /> '• Environmental and Geotechnical Site Investigation Contractors <br /> Gregg In Situ CPT Interpretations as of January 7, 1999 (Release 1.00.19) <br /> r Gregg In Situ's interpretation routine should be considered a calculator of current published CPT <br /> correlations and is subject to change to reflect the current state of practice. The interpreted values are not <br /> considered valid for all soil types. The interpretations are presented only as a guide for geotechnical use <br /> and should be carefully!scrutinized for consideration in any geotechnical design. Reference to current <br />' literature is strongly recommended. <br /> The CPT interpretations are based on values of tip, sleeve friction and pore pressure averaged over a <br /> user specified interval(typically 0.25m). Note that Qt is the recorded tip value, Qc, corrected for pore <br /> pressure effects. Since all Gregg In Situ cones have equal end area friction sleeves, pore pressure <br /> corrections to sleeve friction, Fs, are not required. <br /> s' <br /> j The tip correction is: Qt= Qc+(1-a) •Ud <br /> where: Qt is the corrected tip load <br /> Qdis the recorded tip load <br /> i Ud'is the recorded dynamic pore pressure <br /> i <br /> a is the Net Area Ratio for the cone(typically 0.85 for Gregg In Situ cones) <br /> i Effective vertical overburden stresses are calculated based on a hydrostatic distribution of equilibrium <br /> pore pressures below the water table or from a user defined equilibrium pore pressure profile(this can be <br /> C obtained from CPT dissipation tests). The stress calculations use unit weights assigned to the Soil <br /> Behavior Type zones or,from a user defined unit weight profile. <br /> r Details regarding the interpretation methods for all of the interpreted parameters is given in table 1. The <br /> appropriate references,referred to in table 1 are listed in table 2. <br /> The estimated Soil Behavior Type is based on the charts developed by Robertson and Campanella shown <br /> in figure 1. <br /> Table 1 CPT Interpretation Methods <br /> Interpreted Description Equation Ref <br /> i Parameter <br /> Depth mid layer depth <br /> - ed corrected Av Qt Avera ti <br /> 9 I 9 P(Qt) AvgQt=-7—Qt, <br /> 1 <br /> AvgFs Averaged sleeve friction(Fs) 1 <br /> l <br /> AvgFs=— Fs, <br /> AvgRf Averaged friction ratio(Rf) AvgFs <br /> AvgRf=100%• <br /> 4vgQt <br /> AvgUd I Averaged dynamic pore pressure(Ud) 1 <br /> AvgUd Ud, <br />` SBT Soil Behavior Type as defined by Robertson and Campanella <br /> �I <br /> H <br /> 1 <br /> 9 <br /> i <br />