<p><p><figure id='attachment_2575' style='max-width:1024px' class='caption aligncenter'><img class="wp-image-2575 size-large" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of the excavation of unsuitable material using an excavator in Columbus, Mississippi." width="1024" height="768" /><figcaption class='caption-text'> E
<p><p><strong>Reference(s):<br></strong><em>Brown (2001)<br>Christopher et al. (2008)<br>Holtz et al. (2008)<br>Trenter (2001)<br>WSDOT (2010)</em></p><p>In highway embankment and pavement construction, excavation and replacement is implemented either through planned mitigation of unstable soils based on the site investigation or through mitigation of unstable soils encountered during construction. Some typical uses for excavation and replacement are illustrated in Figure 1 on the following page.
<p><p><h2>Summary of Example Specifications</h2>The FHWA (2003) specification is included in this document as an example; however, all the specifications reviewed are suitable for excavation and replacement. The table below provides information on obtaining all the references included in the review. A brief comment regarding each specification starts on Page 3.</p><p><table class='tablepress' id='tablepress-182'><thead><th>Specification:</th><th>Where to Obtain:</th></thead><tbody><tr><td >American Association of State Highway and Transportation Officials (AASHTO) (2008)</td><td >Available for purchase at:
<a href="https://bookstore.transportation.org/item_details.aspx?ID=1197">https:/…;
</td></tr><tr><td >Federal Highway Administration (FHWA) (2003)</td><td >Available for download at:
<a href=http://flh.fhwa.dot.gov/resources/pse/specs/>http://flh.fhwa.dot.gov/re…;
</td></tr><tr><td >Forest Service (1996)</td><td >Available for download at:
<a href=http://www.fs.fed.us/database/acad/dev/roads/roadscon.htm>http://www.fs…;
</td></tr></tbody></table><br><h3>Table 1. Specification Identification Table</h3><table class='tablepress' id='tablepress-183'><thead><th>Specification type</th><th>Method approach</th><th>Performance approach</th><th>Combined performance/method approach</th><th>Performance level</th><th>Iowa DOT (2009a)</th><th>Iowa DOT (2009b)</th><th>AASHTO (2008)</th><th>FHWA (2003)</th><th>Forest Service (1996)</th></thead><tbody><tr><td >Section 2102. Roadway and Borrow Excavation</td><td ><center><img src="http://geotechtools.geoinstitute.org/app/uploads/2018/03/check-mark.png…; alt="" width="22" height="16" class="alignnone size-full wp-image-479" /></center></td><td ></td><td ></td><td ></td><td ><center><img src="http://geotechtools.geoinstitute.org/app/uploads/2018/03/check-mark.png…; alt="" width="22" height="16" class="alignnone size-full wp-image-479" /></center></td><td ></td><td ></td><td ></td><td ></td></tr><tr><td >Section 2107. Embankments</td><td ><center><img src="http://geotechtools.geoinstitute.org/app/uploads/2018/03/check-mark.png…; alt="" width="22" height="16" class="alignnone size-full wp-image-479" /></center></td><td ></td><td ></td><td ></td><td ></td><td ><center><img src="http://geotechtools.geoinstitute.org/app/uploads/2018/03/check-mark.png…; alt="" width="22" height="16" class="alignnone size-full wp-image-479" /></center></td><td ></td><td ></td><td ></td></tr><tr><td >Section 203. Excavation and Embankment</td><td ><center><img src="http://geotechtools.geoinstitute.org/app/uploads/2018/03/check-mark.png…; alt="" width="22" height="16" class="alignnone size-full wp-image-479" /></center></td><td ></td><td ></td><td ></td><td ></td><td ></td><td ><center><img src="http://geotechtools.geoinstitute.org/app/uploads/2018/03/check-mark.png…; alt="" width="22" height="16" class="alignnone size-full wp-image-479" /></center></td><td ></td><td ></td></tr><tr><td >Section 204.-Excavation and Embankment</td><td ><center><img src="http://geotechtools.geoinstitute.org/app/uploads/2018/03/check-mark.png…; alt="" width="22" height="16" class="alignnone size-full wp-image-479" /></center></td><td ></td><td ></td><td ></td><td ></td><td ></td><td ></td><td ><center><img src="http://geotechtools.geoinstitute.org/app/uploads/2018/03/check-mark.png…; alt="" width="22" height="16" class="alignnone size-full wp-image-479" /></center></td><td ></td></tr><tr><td >Section 203. Excavation, Embankment and Haul</td><td ><center><img src="http://geotechtools.geoinstitute.org/app/uploads/2018/03/check-mark.png…; alt="" width="22" height="16" class="alignnone size-full wp-image-479" /></center></td><td ></td><td ></td><td ></td><td ></td><td ></td><td ></td><td ></td><td ><center><img src="http://geotechtools.geoinstitute.org/app/uploads/2018/03/check-mark.png…; alt="" width="22" height="16" class="alignnone size-full wp-image-479" /></center></td></tr></tbody></table><br><p class="disclaimer"><strong>Performance level:<br></strong><strong>1 - </strong>Actual performance measured after construction (e.g., settlement at a specific time) and warranty provisions might be included<br><strong>2 - </strong>Performance-related properties measured at end of construction (e.g., CPT, vane shear, etc.)<br><strong>3 - </strong>Design properties measured during construction (e.g., modulus measured for each lift)<br><strong>4 - </strong>Design-related properties measured during construction (e.g., density and water content measured for each lift)</p></p><p><div class="grayed-title subsection"><strong>Specification Name/Number:</strong> Iowa DOT Section 2102. Roadway and Borrow Excavation<br>Iowa DOT Section 2107. Embankments</div><strong>Reference(s):<br></strong><em>Iowa DOT (2009a)<br>Iowa DOT (2009b)<br></em>The specifications found from the Iowa DOT are considered to be similar to specifications from state departments of transportation across the U.S. For this example, two specifications were identified from Iowa which are applicable to excavation and replacement.<br><div class="grayed-title subsection"><strong>Specification Name/Number:</strong> Section 203. Excavation and Embankment</div><strong>Reference(s):<br></strong><em>AASHTO (2008)</em>The AASHTO guide specification for excavation and embankment has a description of unsuitable material excavation and describes the process of placing fill material. The specification is applicable to the overall excavation and replacement process, but the specification does not address acceptable materials to be used during replacement.<br><div class="grayed-title subsection"><strong>Specification Name/Number:</strong> Section 204. Excavation and Embankment</div><strong>Reference(s):<br></strong><em>AASHTO (2003)</em>The FHWA guide specification for excavation and embankment generally describes the process of excavation and replacement. In this specification, excavation of unsuitable material is included in the “subexcavation” item. The Subexcavation paragraph describes excavation as directed by the Contracting Officer with subsequent surveying of the excavation followed by backfilling and compaction. The specification does not address acceptable materials to be used during replacement. The FHWA specification is included with this document as an example.<br><div class="grayed-title subsection"><strong>Specification Name/Number:</strong> Section 203. Section 203. Excavation, Embankment and Haul</div><strong>Reference(s):<br></strong><em>Forest Service (1996)</em>The Forest Service guide specification for excavation and embankment has a description of unsuitable material excavation and backfill. The specification is applicable to the overall excavation and replacement process, but the specification does not address acceptable materials to be used during replacement.</p></p>
<p><p><strong>Reference(s):</strong></p><p><em>Christopher et al. (2010)<br>Monahan (1994)<br>Trenter (2001)</em></p><p><strong>Method Summary</strong></p><p>Moisture and density testing of the fill materials should be completed as the fill is placed. Laboratory testing should include the determination of the optimum moisture and maximum dry density of the material, which provides the benchmark for comparison of field moisture and densities.
Excavation and replacement 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 excavation and replacement is used for support of embankments and structures 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>Reference(s):</strong></p><p><em>Trenter (2001)</em></p><p><strong>Method Summary</strong></p><p>Piezometers should be installed to monitor ground water levels during construction. Piezometers can be of any type, such as open pipes or vibrating wire sensors.</p><p><strong>Accuracy and Precision</strong></p><p>The monitoring of the ground water levels is required to determine if any required excavation will extend below the water table.
<p><p><strong>Reference(s):</strong></p><p><em>Christopher et al. (2010)</em></p><p><strong>Method Summary</strong></p><p>The objective of proof rolling is to locate areas with soft or yielding material. The technique can be implemented at any point during earthwork construction. Proof rolling observations can be made simultaneously as material is being excavated, hauled, placed, and compacted by observing the equipment used to perform each of these tasks.
<p><p><strong>Reference(s):</strong></p><p><em>Capachi (1991)<br>Christopher et al. (2010)<br>Monahan (1994)<br>Trenter (2001)</em></p><p><strong>Method Summary</strong></p><p>QC/QA daily logs are a fundamental part of documenting construction during excavation and replacement projects. The daily logs should include a record of the areas excavated, volume of the material excavated, and a description of soils exposed after excavation.
<p><p><strong>Reference(s):</strong></p><p><em>Capachi (1991)<br>Christopher et al. (2010)<br>Monahan (1994)<br>Trenter (2001)</em></p><p><strong>Method Summary</strong></p><p>The site should be surveyed in order to document excavated areas and record fill placement elevations.
![https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…](https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/ER2-1024x768.jpg"){kind=link}
![http://geotechtools.geoinstitute.org/app/uploads/2018/03/check-mark.png…](http://geotechtools.geoinstitute.org/app/uploads/2018/03/check-mark.png"){kind=link}