<p><p><strong>Reference(s):</strong></p><p><em>Bjerrum et al. (1967)<br>Glendinning et al. (2005)<br>Lo et al. (2001b)</em></p><p><strong>Method Summary</strong></p><p>The references above documented the use of Vane Shear Test (VST) to measure undrained shear strength of cohesive soils before, during, and after treatment. VST is widely used in geotechnical engineering practice (ASTM D2573-08) to evaluate rapid loading strength of saturated fine-grained clays and silts with undrained shear strength less than 200 kPa. This method is not applicable for sands, gravels or other coarse-grained soils. The test equipment consists of four thin, equally sized plates welded to a torque rod. The vanes are normally built of steel. The ends of the vane may be flat or tapered. The test is often performed in drilled boreholes or with self-push or self-drilling or pushed (vane shoe) methods. Hand-held vane devices can also be used for shallow depths, but they are less accurate, as it is more difficult to maintain vane/rod stability and verticality. The test procedure involves inserting the vane to the desired depth and then applying torque (T) at the top of the torque rod to rotate the vane at a uniform speed. A cylinder of soil height (H) and diameter (D) will resist the torque until the soil fails. The peak undrained shear strength is calculated using the T_max, D, and H measurements. Remolded shear strength can also be determined by obtaining torque values after rotating the vane rapidly for a minimum of five to ten revolutions. The ratio of peak and residual shear strengths gives a measure of the sensitivity of the soil. ASTM D2573-08 recommends selecting the size of the vane depending on the soil being tested – softer soil requires larger vane diameter. Rate of rotation affects the results. The vane shear strength values are influenced by the plasticity of the soil especially for soils with Plasticity Index (PI) &gt; 5%. ASTM D2573-08 provides guidelines to correct the values if the PI is known.</p><p><strong>Accuracy and Precision</strong></p><p>ASTM D2573-08 standard indicates that precision of this test procedure cannot be determined due to the nature of the test method. The standard also indicates that the accuracy of the VST results cannot be determined as no accepted reference value is available.</p><p><strong>Adequacy of Coverage</strong></p><p>It represents soil properties only at the test location depth. In relatively uniform soil deposits, the number of tests required can be limited. Number of tests should be increased with increasing heterogeneity in the subsurface layers.</p><p><strong> </strong><strong>Implementation Requirements </strong></p><p>These tests are easy and rapid to perform. If tests are needed at greater depths, a drill rig will be needed to drill a hole to the desired depth. Soils at shallow depths can be tested by pushing the vane rod directly into the soil.</p><p><strong>General Comments </strong></p><p>This method can be effective for QA. Tests performed prior to and after treatment can be useful in assessing the relative improvement in soil properties due to treatment. It is important to note that the test method is applicable to fine-grained soils with undrained shear strengths less than 200 kPa.</p></p>