<p><p><strong>References:<br></strong><em>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. PressureMeter Tests (PMTs) may be used to verify soil improvement as indicated by the horizontal earth pressure and resistance before and after stone column installation. 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 for increasing the strength of cohesive soils and function primarily as reinforcing elements. PMTs are not typically performed when stone columns are installed in cohesive soils.</p><p><strong>Accuracy and Precision</strong></p><p>When combined with local experience and judgment, the PMT can provide accurate and precise information about soil stiffness. Quality of test results is dependent on disturbance of the PMT borehole sidewalls.</p><p><strong>Adequacy of Coverage</strong></p><p>The PMT only allows interval, rather than continuous, testing.</p><p><strong>Implementation Requirements </strong></p><p>The PMT is not as readily available as other in-situ testing methods such as the SPT or the CPT. It is also more time-consuming and costly.</p><p><strong>General Comments</strong></p><p>The PMT provides a measure of soil stiffness, making it useful for verifying quality for slope stabilization, support of structures, support of embankments, settlement reduction, liquefaction mitigation, and prevention of lateral spreading.</p></p>