A CASE STUDY ON THE CONSTRUCTION AND FIELD LOADING TEST OF WAVEFORM MICROPILE-Paper

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The study evaluates the field construction and loading performance of a waveform micropile, which uses jet grouting to form enlarged “shear keys” along the pile shaft. This shape is intended to improve ground contact and increase shaft resistance compared with conventional micropiles.<br /><br />A total of 96 piles were installed as foundations for a highway bridge abutment in South Korea, where limited working space prompted a change from the originally planned steel pipe piles. The piles had a 300 mm shaft and 500 mm shear keys, with steel casing in the upper 2 m. Design calculations indicated allowable capacities of approximately 800 kN and 733 kN per pile for the two site groups, exceeding the project’s 400 kN vertical load; analysis also predicted adequate lateral resistance.<br /><br />Installation involved waterjet drilling, jet grouting to create the waveform profile, and placement of steel reinforcement. Grouting pressure was approximately 400 bar. Vertical pull-out and lateral loading tests were conducted to verify performance. At the 400 kN design load, measured vertical displacements were 4.3 mm and 2.2 mm, well below the applicable 40–50 mm tolerances. At a lateral load of 60 kN, displacements were 7.9 mm and 0.5 mm, also below the 25–38 mm criteria. Tests reached about 640 kN vertically and 76 kN laterally, but were intended as verification tests and did not establish ultimate capacity.<br /><br />The results indicate that waveform micropiles could be installed efficiently in the field and provided adequate vertical and lateral performance for the abutment application.

Keywords

waveform micropile

jet grouting

shear keys

micropile loading test

field construction

shaft resistance

highway bridge abutment

vertical load performance

lateral load resistance

South Korea