<p><p><strong>References:<br></strong><em> Schaefer et al. (2016)<br>Mitchell (1981)<br>SHRP 2-Phase I Technology Assessment (2008)</em></p><p><strong>Method Summary</strong></p><p>The backfill gradation can be verified using a grain size analysis in the lab and using the resulting grain sizes to determine its suitability number (S_N).

<p><p><strong>References:<br></strong><em> Schaefer et al. (2016)<br>Massarsch and Fellenius (2001)<br>Massarsch and Fellenius (2005)<br>Massarsch and Heppel (1991)<br>Mitchell (1981)<br>SHRP 2-Phase I Technology Assessment (2008)</em></p><p><strong>Method Summary</strong></p><p>The Cone Penetration Test (CPT) is a field method to directly measure the soil resistance. In this test a small diameter cone is pushed into the ground at a constant rate.

<p><p><strong>Current FHWA Reference(s):<br></strong><em>Schaefer et al. (2016)</em>.<br><strong>Supporting Reference(s):<br></strong><em>Massarch and Fellenius (2001)<br>Massarch and Fellenius (2005)<br>Massarch and Heppel (1991)<br>Schaefer et al. (1997)</em></p><p>Table 4-8 in Schaefer et al. (2016) provides relationships between CPT cone resistance values and design‑related soil properties (relative density, dry unit weight, CSR and shear wave velocity).

<p><p><strong>References:<br></strong><em> Schaefer et al. (2016)<br>Massarsch and Heppel (1991)<br>Mitchell (1981)</em></p><p><strong>Method Summary</strong></p><p>The cross-hole test is an in-situ measurement of the wave propagation velocity at small strains between bore holes. Typically, two holes are drilled, cased, and a source is placed in one hole and a receiver in the other hole. The wave is generated from the source and the time for the wave to reach the receivers is evaluated.

<p><p><strong>References:<br></strong><em> Schaefer et al.

<p><p><figure id='attachment_3606' style='max-width:6876px' class='caption aligncenter'><img class="wp-image-3606 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Schematic diagram of the generic vibrocompaction process." width="6876" height="4012" /><figcaption class='caption-text'> Generic vibrocompaction process.

Liquefaction Potential Assessment

Vibrocompaction may be used at sites with in-situ soils that may be susceptible to liquefaction during earthquakes. Saturated sands, silty sands, sandy silts, and silts are likely to be in this category. When vibrocompaction is used for support of embankments and structures or to reduce settlements, it is also necessary to confirm that there will not be a risk of liquefaction or other ground disturbance that could lead to loss of support and lateral spreading.

<p><p><strong>References:<br></strong><em> Schaefer et al.

<p><p><strong>References:<br></strong><em> Sheu et al. (1986)<br>SHRP 2-Phase I Technology Assessment (2008)</em></p><p><strong>Method Summary</strong></p><p>Spectral analysis of surface wave (SASW) method is a non-destructive, in-situ measurement of the shear wave velocity. Geophones and a wave propagation source are placed on the site’s surface. The time is evaluated for the direct, reflected, and refracted surface waves to arrive to the geophone from the source.

<p><p><strong>Current FHWA Reference(s):<br></strong><em>Schaefer et al. (2016)</em>.<br><strong>Supporting Reference(s):<br></strong><em>Mitchell (1981)<br>Schaefer et al. (1997)</em></p><p>Table 4-8 in Schaefer et al. (2016) provides relationships between (N₁)₆₀ values and design‑related soil properties (relative density, dry unit weight, CSR and shear wave velocity).

<p><p><strong>References:<br></strong><em> Schaefer et al. (2016)<br>Massarsch And Fellenius (2001)<br>Mitchell (1981)<br>SHRP 2-Phase I Technology Assessment (2008)</em></p><p><strong>Method Summary</strong></p><p>The Standard Penetration Test (SPT) is a field method to directly measure the soil resistance to penetration and obtain disturbed samples. The test is performed by hammering a standard “split-spoon” sampler into the ground in three six-inch increments.

<p><p><strong>References:<br></strong><em> Schaefer et al.

<p><p><h2>Commentary</h2>The cost of vibrocompaction is typically captured in a contract bid item which is measured by the lineal foot.

<p><p><figure id='attachment_2637' style='max-width:740px' class='caption aligncenter'><img class="wp-image-2637 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Schematic diagram showing the mail elements of vibratory compaction equipment." width="740" height="520" /><figcaption class='caption-text'> Main elements of vibratory compa