Cone Penetrating Testing (2007) / Chapter Skim
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29 Soils are very complex materials because they can be comprised of a wide and diverse assemblage of different particle sizes, mineralogies, packing arrangements, and fabric. Moreover, they can be created from various geologic origins (marine, lacustrine, glacial, residual, aeolian, deltaic, alluvial, estuarine, fluvial, biochemical, etc.)
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direct methods such as the downhole geophysics test and SCPT. However, in some instances, it may be necessary to estimate the Vs profile by means of an empirical correlation if a seismic penetrometer is not available.
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31 should be used with caution in sands and that mineralogy and cementation can be important facets of geomaterials. For saturated soils, the correlation in Figure 30 is based on a large data set of soils, including soft to stiff clays and silts, loose to dense sands and gravels, as well as mixed geomaterials (n 727; r2 0.808)
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In lieu of shear modulus, the stiffness can be expressed in terms of an equivalent Young's modulus of soil through elastic theory: Emax 2Gmax (1 )
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33 An equivalent stiffness of soils is also afforded by means of the constrained modulus (D) obtained from one-dimensional consolidation tests.
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with assigned values of G ranging from 0.02 for the organic plastic clays up to 2 for overconsolidated quartz sands. In the future, additional studies with multiple regression, artificial neural networks, and numerical modeling may help guide the development of more universally applied global relationships.
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35 Midface Filter Element: σp′ = 0.75 (qt − u1)
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An example of the procedure for evaluating stress history from cone tip stress measurements in clean sands is afforded from a quarry site near Stockholm investigated by Dahlberg (1974)
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37 all soil types may be considered in a consistent manner, whereas the separation of soil layers into "clay-like" and "sand-like" often result in mismatched profiles of preconsolidation stress with depth. EFFECTIVE STRESS STRENGTH Sands The strength of soils is controlled by the effective stress frictional envelope, often represented in terms of the Mohr– Coulomb parameters: effective friction angle and c effective cohesion intercept.
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of an inverted bearing capacity (BC) theory supplemented with CPT calibration chamber data from five sands (Robertson and Campanella 1983)
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39 An approximate form for a deterministic line-by-line evaluation of f for the NTNU method is given by (Mayne and Campanella 2005) : (degrees)
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footings, and excavations, it has been shown that the mobilized undrained shear strength may be taken simply as (Trak et al. 1980; Terzaghi et al.
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41 SENSITIVITY In soft clays and silts, the sensitivity (St) is considered as an index to problematic construction and field performance difficulties.
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42 FIGURE 47 Relative density of undisturbed (frozen) quartz sands versus normalized cone tip resistance.
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43 The Kp limit is shown in Figures 49 and 50 for the K0 − OCR relationships for clays and sands, respectively. Illustration of the approach for K0 profiling in sands by CPT is afforded from the previous case study of quarried glacial sand near Stockholm (Dahlberg 1974)
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may be assessed from the stress history (Mayne and Stewart 1988; Mesri and Abdel-Ghaffar 1993)
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45 horizontal to vertical permeability to address possible issues of anisotropy during interpretation. The study compared laboratory-determined results with the SPM solution (Teh and Houlsby 1991)
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46 For sands, the operational rigidity index can be evaluated from the Vs measurement using calibrations based on undisturbed frozen sand specimens (Mayne 2006b)
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47 For this approach, results from piezo-dissipation testing are used together with an appropriate rigidity index to evaluate cvh, and an estimate of D is obtained from either of the relationships with net cone resistance or small-strain shear modulus (or both) , as discussed previously.
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(e.g., Vreugdenhil et al.
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