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From page 164... ... 164 C H A P T E R 9 Evaluation of Soil Properties Introduction The mechanical behavior of soils under loading is represented by a suite of parameters that have been established within the context of theoretical backgrounds, primarily via elasticity, plasticity, and cavity expansion, but also using Winkler spring analogies and subgrade reaction models. The assigned values of these parameters can then be used in a variety of engineering analyses, such as stability, foundation bearing capacity, settlement, and time rate of consolidation. Read the entire page →
From page 165... ... 165 and, thus, is not intended to be exhaustive. Geotechnical aspects of highway projects are often concerned with pilings, shallow foundations, slopes, earth-retaining structures, roadways, and embankments. Read the entire page →
From page 166... ... 166 Source: Ilmar Weemees, Vancouver, BC Figure 9-1. Example subsurface profile developed from a 2D MASW survey 9.2.2 In Situ Tests Direct-push, in situ tests, such as CPT and DMT, offer improved resolution of the stratigraphy because the measurements are taken at higher vertical frequencies and multiple readings are obtained from each sounding. Read the entire page →
From page 167... ... 167 9.2.3 Soil Borings A traditional means of defining subsurface stratigraphy is to conduct a series of soil borings and interpolate or extrapolate the interfaces between the various soil zones or strata (Figure 9-3) Read the entire page →
From page 168... ... 168 Soil Classification Traditionally, soil is classified based on recovered soil samples (both drive type and undisturbed tube samples) based on the USCS and AASHTO classification systems as described in Chapter 8. Read the entire page →
From page 169... ... 169 Source: adapted from Robertson (2009a) Figure 9-4. Read the entire page →
From page 170... ... 170 Source: Paul Mayne Figure 9-5. Use of CPT material index Ic and algorithms for nine-zone soil behavioral chart Initially the value of Ic is calculated using n = 1.0 (i.e., the original definition of Q) Read the entire page →
From page 171... ... 171 • Zone 3 (clays: 2.95 ≤ Ic < 3.60) • Zone 4 (silt mixtures: 2.60 ≤ Ic < 2.95) Read the entire page →
From page 172... ... 172 9.4.1 Unit Weight from Shear Wave Velocity Total unit weight is correlated to shear wave velocity (Vs) , as illustrated by Figure 9-6 using data reported in Mayne et al. Read the entire page →
From page 173... ... 173 Source: after Mayne (2014) Note: 1 atm = 1.058 tsf = 1.013 bars = 101.3 kPa = 14.7 psi Figure 9-7. Read the entire page →
From page 174... ... 174 Source: Mayne et al. Read the entire page →
From page 175... ... 175 Source: after Mayne et al. Read the entire page →
From page 176... ... 176 Source: Mayne (2017) Figure 9-10. Read the entire page →
From page 177... ... 177 Source: after Mayne et al. Read the entire page →
From page 178... ... 178 Source: Mayne (2007a) Figure 9-12. Read the entire page →
From page 179... ... 179 Source: after Mayne (2007b) Figure 9-13. Read the entire page →
From page 180... ... 180 For CPT soundings in sands, the standard penetration rate of 0.787 in./s (20 mm/s) is essentially a drained condition (∆ = 0) Read the entire page →
From page 181... ... 181 Source: Paul Mayne Figure 9-15. Effective stress friction angle of clays from CPTu via NTH solution The rigorous NTH solution for = 0 and = 0° (i.e., constant volume) Read the entire page →
From page 182... ... 182 Source: Ouyang and Mayne (2018a) Figure 9-16. Read the entire page →
From page 183... ... 183 Source: Paul Mayne Figure 9-17. Effective friction angle of sands from DMT horizontal stress index For DMT in clays, a nexus has been established between the CPTu and DMT via spherical cavity expansion (SCE) Read the entire page →
From page 184... ... 184 Source: Ouyang and Mayne (2018b) Figure 9-18. Read the entire page →
From page 185... ... 185 Source: Paul Mayne Figure 9-19. Empirical relationship for effective friction angle of sands from stress-normalized SPT N60 value using data from undisturbed sampling techniques Total Stress Strength Parameters The undrained shear strength of fine-grained soils can be estimated via (i) Read the entire page →
From page 186... ... 186 Because the ratio of 0.1 < ⁄ < 0.2 for many soils, the value of Λ is within the range: 0.8 ≤ Λ ≤ 0.9. Figure 9-20 shows a summary of normalized undrained shear strengths with OCR from several clays tested via DSS tests. Read the entire page →
From page 187... ... 187 As shown in Figure 9-21, the cone factor decreases with according to the following: = 10.5 − 4.6 + 0.1 Source: Mayne and Peuchen (2018) Figure 9-21. Read the entire page →
From page 188... ... 188 = where f1 = an empirical parameter that depends upon the geologic setting, plasticity, origin, and other aspects of the clay formation While f1 has been correlated with PI (in percent) , results reported by Sowers (1979) Read the entire page →
From page 189... ... 189 • Paired sets of directional shear waves In lieu of direct measurement of , the value may be estimated from the relationship shown in Figure 9-23 and given by the following expression, which applies to soils that have been loaded-unloaded: = (1 − ʹ) ∙ ʹ ≤ where = (1 + ) Read the entire page →
From page 191... ... 191 = ∙ = 2 (1 + ) The values of or can be obtained from undisturbed soil samples in the laboratory using resonant column tests (Section 8.9.1) Read the entire page →
From page 192... ... 192 Source: Mayne (2007b) Figure 9-25. Read the entire page →
From page 193... ... 193 This relationship is corroborated by an independent CPT-DMT study by Robertson (2009b) shown in Figure 9-26 and approximated by the following: ≈ 5 ∙ ( − ) Read the entire page →
From page 195... ... 195 sources, such as (i) back-calculated values of E' from field performance of foundations, (ii) Read the entire page →
From page 196... ... 196 Source: Paul Mayne Figure 9-29. Rigidity index from spherical cavity expansion (SCE-CSSM) Read the entire page →
From page 197... ... 197 slug tests as described in Chapter 7, or using push-in piezometers or piezocone penetration tests with dissipation measurements (Mayne et al. Read the entire page →
From page 198... ... 198 t = measured time to reach the selected U The respective radii for 10-cm2 and 15-cm2 cone penetrometers are ac = 1.78 cm and ac = 2.20 cm. For a monotonic response, the various time factors ( ) Read the entire page →
From page 199... ... 199 Source: Paul Mayne Figure 9-32. Definitions of monotonic vs. Read the entire page →
From page 200... ... 200 An example of the dissipation of DMT A-readings is shown in Figure 9-34 (Marchetti and Totani 1989) , illustrating the selection of the = at the inflection point of the curve. Read the entire page →
From page 201... ... 201 Source: relationship from Parez and Fauriel (1988) Figure 9-35. Read the entire page →
From page 202... ... 202 Special Considerations Under certain circumstances, the interpretation of laboratory and field tests will require special attention, especially for soils with complex behavior and constituency, including organic clays, sensitive fine-grained soils, collapsible geomaterials, lateritic and residual soils, loess, and other types of problematic soils. For fissured clays that have experienced landsliding and undergone slope failure, the use of residual strength parameters (ϕr' and cr' = 0) Read the entire page →
From page 203... ... 203 Chapter 9 References Amoroso, S Read the entire page →
From page 204... ... 204 Mayne, P.W. Read the entire page →
From page 205... ... 205 Sowers, G.F. Read the entire page →

From page 164...

... 164 C H A P T E R 9 Evaluation of Soil Properties Introduction The mechanical behavior of soils under loading is represented by a suite of parameters that have been established within the context of theoretical backgrounds, primarily via elasticity, plasticity, and cavity expansion, but also using Winkler spring analogies and subgrade reaction models. The assigned values of these parameters can then be used in a variety of engineering analyses, such as stability, foundation bearing capacity, settlement, and time rate of consolidation.