<p><p><strong>References:<br></strong><em>Briaud and Seo (2003)<br>Mooney et al. (2010)<br>Peterson et al. (2006)<br>Rahman et al. (2008)<br>Ryden and Mooney (2007)<br>White et al. (2007a, 2008d, 2010)</em></p><p><strong>Method Summary </strong></p><p>Soil Stiffness Gauge (SSG), Briaud Compaction Device (BCD), and seismic methods fall under this category. These tests typically involve calculating modulus at relatively low strains.</p><p>BCD test is performed by placing a 150-mm diameter plate on the ground, applying the load (a minimum load of 223 N), and measuring the applied load and the bending strain in the plate to determine the modulus. SSG device weights about 10 kg, is 28 cm in diameter, and 25.4 cm in height and rests on a ring-shaped foot on the soil surface. The SSG produces high frequency vibrations (100 to 200 Hz) that produce small changes in vertical force and deflections used to determine stiffness and modulus values. Seismic methods involve estimating Young’s or shear moduli using different wave propagation methods: (1) impact echo, (2) impulse response, (3) spectral analysis of surface waves, (4) ultrasonic surface wave, or (5) ultrasonic body wave velocity. Very limited studies documented correlations between SSG, BCD, and seismic test results and CCC measurements (e.g., Ryden and Mooney 2007, Mooney et al. 2010, White et al. 2007a, 2008d).</p><p><strong> </strong><strong>Accuracy and Precision</strong></p><p>Accuracy and precision of these devices is not quantified in the literature. Correlation results between these test methods and conventionally used modulus test methods (e.g., static plate load test) are limited in the literature.</p><p><strong> </strong><strong>Adequacy of Coverage</strong></p><p>Number of tests depends on the variability observed, but generally it requires many tests to adequately characterize the spatial variability of soils. These tests are relatively fast to perform (approximately &lt; 5 min per test).</p><p><strong> </strong><strong>Implementation Requirements </strong></p><p>Special equipment and setup and trained personnel are necessary to conduct the test and analyze the results. SSG and BCD require less specialized training, but seismic methods generally require more training.</p><p><strong> </strong><strong>General Comments</strong></p><p>This test method provides a direct measure of elastic modulus and can serve as a good QA tool if correlations between small-strain modulus and conventionally used modulus measurements can be developed.</p></p>