<p><p><strong>References:<br></strong><em>Hansbo and Pramborg (1980)<br>Hossain et al. (2006)<br>NCHRP 21-09 (2010)<br>Newman and White (2008)<br>Peterson et al. (2006)<br>Rahman et al. (2008)<br>Thompson and White (2007)<br>Thompson and White (2008)<br>Vennapusa et al. (2009)<br>Vennapusa et al. (2010)<br>White and Thompson (2008)<br>White et al. (2005, 2006, 2007a, 2007b, 2008a, 2008b, 2008c, 2009a, 2009b, 2009c, 2009d)</em></p><p><strong>Method Summary</strong></p><p>Static cone penetration tests (CPT) and dynamic cone penetration (DCP) fall under this category. These tests have been used to assess soil shear strength properties or stiffness/modulus in compacted earth fill in comparison with roller-integrated compaction measurements. CPT is widely used for many geotechnical applications and can measure soil properties up to deeper depths (&gt;30 m), while DCP is generally used in pavement foundation layer construction QA process and can measure soil properties up to 2m. These procedures may have difficulties with penetration when large particles or boulders are encountered in the subsurface (see White et al. 2007a).</p><p>CPT is described in ASTM D3441. CPT involves pushing an instrumented cone trip into the ground at a controlled rate and recording the sleeve friction and tip resistance of the cone almost continuously (about every 2 cm). Some modern electronic CPT cones now employ a pressure transducer to record pore water pressure data and is commonly referred to as CPTU method. The sleeve friction and tip resistance values have been correlated to soil classification and elastic modulus in the literature. One disadvantage of CPT is that it requires specialized equipment and personnel, and is relatively more time consuming than DCP.</p><p>DCP test method is described in ASTM D6951. DCP test method involves driving a cone trip into the soil by lifting an 8 kg sliding hammer to 575 mm drop height and then releasing it. The total penetration for a given number of blows is then measured and recorded as mm/blow. ASTM D6951 provides correlations between California bearing ratio (CBR) and mm/blow for different soil types. Correlations between DCP and undrained shear strength and modulus are documented in the literature.</p><p>Many case studies documented correlations between CBR determined from DCP (for the compaction layer thickness) and roller-integrated compaction measurements. The correlations sometimes were relatively strong and sometimes were relatively weak (as assessed by coefficient of determination R2 value). Of the many other factors that can contribute to scatter in correlation analysis, heterogeneity in the underlying layers is identified as a major factor that contribute to weak correlations (see NCHRP 21-09 2010). However, penetration tests are effective in detecting deeper “weak” areas (at depths &gt; 300 mm).</p><p><strong>Accuracy and Precision</strong></p><p>Accuracy of these test methods is hard to determine. ASTM D6951 indicate that the repeatability standard deviation of the DCP test is less than 2 mm/blow. For CPT tests conducted by different laboratories on same soil a variation of about ±10% has been reported in the literature [see Renzi, R., Corte, J. F., Rault, G., Bagge, G., Gui, M. &amp;Laue, J. (1994). “Cone penetration tests in the centrifuge: experience of five laboratories.” Proceedings of the international conference on the centrifuge, Singapore, pp. 77- 82].</p><p><strong>Adequacy of Coverage</strong></p><p>Sufficient evaluation requires many tests. The number of tests depends on the observed variability. Penetration tests are advantageous in assessing improvement in soil properties to greater depths than other tests at surface (e.g., density and static and dynamic plate load tests). DCP tests are comparatively economical than CPT, but can only measure soil properties to a depth of about 1 m and up to 2 m with extension rods. Penetration tests capture better vertical variability in a single test compared to other test methods, but coverage spatially is low.</p><p><strong>Implementation Requirements</strong></p><p>Some experience and special equipment is necessary. DCP test can be run by one or two persons and requires some training. CPT requires specialized equipment and personnel with adequate training.</p><p><strong>General Comments</strong></p><p>Empirical correlations can be used to relate results from the penetration tests to soil engineering properties (e.g., soil strength, bearing capacity, stiffness/modulus, liquefaction susceptibility, etc.). Results from DCP have been correlated to roller-integrated compaction measurements. These test methods can serve as good QA tools. Its applicability to each of the potential application is rated below.</p></p>