<p><p><strong>References:<br></strong><em>Al-Homoud and Degen (2006)<br>Kumar (2001)<br>Schaefer et al. (2016)</em></p><p><strong>Method Summary</strong></p><p>Installation of stone columns in clean to silty sands (less than 15% fines) can densify the surrounding soil, resulting in higher strengths and densities. Standard Penetration Tests (SPTs) can be conducted on the soil between stone column locations before and after treatment to validate soil improvement through an increase in blow counts. It is important that locations be identical before and after treatment to provide an accurate depiction of the level of improvement. Though stone columns may increase the strength of some cohesive soils, several months or more may be required before the beneficial effect is observed (Barksdale and Bachus 1983a). Therefore, stone columns are not considered an effective means of increasing the strength of cohesive soils and function primarily as reinforcing elements. SPTs are not typically performed when stone columns are installed in cohesive soils.</p><p><strong>Accuracy and Precision</strong></p><p>Accuracy and precision are limited by the procedure and mechanics of standard penetration testing.</p><p><strong>Adequacy of Coverage</strong></p><p>The SPT is a relatively costly QC/QA technique and does not provide continuous profiling. So, the number of locations evaluated is limited.</p><p><strong>Implementation Requirements </strong></p><p>The SPT is widely used and the equipment is typically readily available.</p><p><strong>General Comments</strong></p><p>The SPT provides correlations to soil strength and density, making it useful for evaluating soil improvement for slope stabilization, support of structures, support of embankments, settlement reduction, liquefaction mitigation, and prevention of lateral spreading. This method is not suitable for assessing properties of saturated cohesive soils between columns.</p></p>