<p><p><strong>References:<br></strong><em>Bruce et al. (1993)<br>Gibler et al. (2005)<br>Gomez et al. (2008a, 2008b)<br>Sabatini et al. (2005)</em></p><p><strong>Method Summary</strong></p><p>A micropile can be partitioned into two zones: the cased or free length in the upper part of the micropile and the bond length in the lower. A portion of the bond length is referred to as the effective bond length wherein the load applied to the micropile is transferred to the surrounding ground.

Current FHWA Reference(s):
Bruce and Juran (1997)
Sabatini et al. (2005)Supporting Reference(s):
Bruce (1997b)
Juran et al. (1999)
Lizzi (1982)
Mason and Bruce (2001)

<p><p><strong>References:<br></strong><em>Bruce (1997b)<br>Bruce and Juran (1997)<br>Gomez et al. (2008a, 2008b)<br>Sabatini et al. (2005)</em></p><p><strong>Method Summary</strong></p><p>A creep test is performed by measuring the movement of the micropile at a constant load over a specified period of time. Creep tests are conducted as part of ultimate, verification, and proof tests at specified load increments.

<p><p><strong>References:<br></strong><em>Bruce (2003b)<br>Bruce and Juran (1997)<br>Cadden et al. (2004)<br>DFI-ADSC (2002)<br>Gibler et al. (2005)<br>Gomez et al. (2008a, 2008b, 2004)<br>Sabatini et al.

<p><p><h2>Project Summary/Scope:</h2>Hollow-core bar micropiles (Type E) were used to retrofit four existing bridges. Underpinning of the foundations was necessary due to deterioration of the exposed section of the existing concrete precast piles. Limited headroom and difficult access provided challenges to retrofitting the bridge foundations. Hollow-core bars were selected to retrofit the bridge because they have faster installation rates.</p><p>Subsurface Conditions: Soft organic silt extended anywhere from 10 to 17 feet.

<p><p><strong>References:<br></strong><em>Bruce (1997b)<br>Bruce and Juran (1997)<br>Cadden et al. (2004)<br>DFI-ADSC (2002)<br>Gibler et al. (2005)<br>Gomez et al. (2008a, 2008b)<br>Sabatini et al. (2005)</em></p><p><strong>Method Summary</strong></p><p>Sabatini et al. (2005) lists what must be observed and recorded as part of grout inspection.

<p><p><strong>References:<br></strong><em>Bruce and Juran (1997)<br>Gibler et al. (2005)<br>Gomez et al. (2008a, 2008b)<br>Sabatini et al. (2005)</em></p><p><strong>Method Summary</strong></p><p>Cube testing is traditionally performed as part of grout inspection and is used to verify the unconfined compressive strength of the grout. Cube testing can take place to confirm acceptability of the grout mix as part of verification, ultimate, and proof load tests.

<p><p><strong>References:<br></strong><em>Bruce (1997b)<br>Bruce and Juran (1997)<br>Cadden et al. (2004)<br>Gomez et al. (2008a, 2008b)<br>Sabatini et al. (2005)</em></p><p><strong>Method Summary</strong></p><p>A specific gravity test is performed as part of grout inspection and is used to confirm the water content (i.e. water-cement ratio) of the grout.

<p><p><strong>References:<br></strong><em>Bruce (1997b)<br>Bruce and Juran (1997)<br>Sabatini et al.