<p><p><h2>QC/QA Guidelines</h2>The quality control and assurance of micropile projects is basic and reliable. In general, a comprehensive QC/QA program verifies that system components adhere to material specifications, installation methods follow execution specifications, and short-term performance specifications have been satisfied which confirm design values. A large component of quality assurance is reviewing inspection documents for completeness and consistency in construction methods and expected site conditions. Bruce and Juran (1997) and Sabatini et al. (2005) are considered to be the guidance documents for a typical QC/QA program for a micropile project. Sample testing program specifications, inspection logs, and suggested test frequencies are described in Sabatini et al. (2005).</p><p>Adherence to material specifications is verified through visual inspection logs and material tests. The installation process for every micropile must be meticulously observed with all necessary information recorded in drilling logs. The drilling logs can be used later to reveal any deviation in the installation process that may affect pile performance. “Although micropile load testing is relatively quick and inexpensive, it is not practical or economic to test every element installed. It is therefore essential that close attention is paid to the quality of the materials and the construction at all stages of the work” (Bruce and Juran 1997). During drilling inspection, the joints in micropiles should be inspected to ensure the pile materials are tight and the thread bar couplers are centered on the bar. If the thread bar couples are not centered on each bar they could slip off upon loading resulting in failure. An evaluation of the grout quality is of paramount importance because the grout serves to transfer the load from the reinforcement to the ground amongst other actions. Compressive strength testing has been traditionally conducted to confirm the strength of the grout. A detraction of this test is that it is a retrospective test. Compressive strength value from cube testing can only be established at a minimum of 48 hours after sampling and normally at 28 days. Specific gravity tests provide the benefit of rapidly assessing the conformance of the grout to design specifications prior to grouting and are preferred. It is recommended to conduct “classification” cube tests during the early stages of construction and then progress to relying wholly on specific gravity tests.</p><p>Short-term performance measures of Case 1 micropiles include static load proof and creep tests, which are conducted during construction. Production micropiles are subject to proof tests. The information gained from proof tests is used to verify acceptable micropile capacity and consistent installation procedures. Typically, proof tests load the micropile to 150% of the design load. Ultimate and verification tests are static load tests performed prior to production pile installation and are used to verify or develop design values. Should ultimate and verification tests disclose unanticipated behavior, the design of production micropiles can be modified. Ultimate tests are run to geotechnical failure and verification tests load the micropile to 200 to 250% of the design load. Ultimate, verification, and proof tests may consist of compression, tension, or lateral loads. Tension tests are usually less expensive because the ground may be used in place of reaction piles or tie-down anchors. Tension load tests can often be used with similar results as compression load tests. Creep tests are performed as part of ultimate, verification, and proof tests. The effective bond length and apparent elastic length of the micropile can be estimated using static load test results. Although not commonly used, telltales can be installed at discrete depths on the micropile to provide information about micropile axial displacement with depth during a static load test. Strain gauges can also be mounted along the micropile to provide information about the axial load distribution with depth. Sabatini et al. (2005) recommend load testing be performed on Case 1 micropiles used for slope stabilization; however, “required micropile side resistance has relied exclusively on contractor experience in similar ground.”</p><p>Hammer-based integrity tests, for example PDA and Statnamic tests, are significantly cheaper to perform and have been used to determine micropile capacity. In an effort to reduce project cost, PDA and Statnamic tests can be incorporated into the testing program in place of static load tests. However, the use of hammer-based integrity tests are less common than static load tests, require considerable interpretation, and may not always be appropriate because of the damage which can be sustained by the micropile as a result of the test.</p><p>Inclinometers can also be used as part of short term monitoring of slope stabilization projects. Inclinometers are especially important for monitoring Case 2 micropiles where it is less meaningful to test each individual micropile because the micropiles and the soil act together as a composite soil-pile mass. Long-term monitoring is typically reserved for slope stabilization projects.</p></p>