<p><p><strong>Reference(s):</strong></p><p><em>Haramay et al. (2009)</em></p><p><strong>Method Summary</strong></p><p>This is a newly developed non-destructive method known as High Definition Imaging (HDI). It involves collecting and analyzing seismic data pre- and post-grouting. It is relatively inexpensive, but requires some experience with geophysics and specialized equipment. 2-D and 3-D seismic refraction surveys are performed and processed into a volumetric 3-D assessment of the site. Geophones are used to collect the data on the surface, and a source, such as a sledge hammer, is used to generate a surface wave. The travel time to each geophone from the source is recorded. Tomographic analysis software was developed for this application to generate more accurate images. Travel times must be picked from the data recorded. HDI allows for time, frequency, and velocity filters to be used with advanced algorithms to automatically pick consistent travel times. A tomographic inversion is performed after the travel times are chosen by the software. Waves are propagated from each source and receiver to find regions having a significant effect on travel time. Images of the velocity contours are developed for analysis by the engineer. A change in velocity typically indicates an increase in strength and modulus of the soil.</p><p>Note: The HDI software developed is available from Summit Peak Technologies (<a href="http://www.summitpeak.net">www.summitpeak.net</a&gt;)</p><p><strong>Accuracy and Precision</strong></p><p>This method is very accurate with the right equipment.</p><p><strong>Adequacy of Coverage</strong></p><p>This method is an excellent method to determine the areas improved, as a full 3-D image of the improved zones can be developed.</p><p><strong>Implementation Requirements </strong></p><p>The equipment for this procedure can be expensive, but if it is available this method is relatively economical to implement.</p><p><strong>General Comments</strong></p><p>This method is very useful, but requires knowledge of geophysics. It is not widely accepted in practice, but may provide the best way of determining the extents of the improved zones</p></p>