Driven-grouted micropile (DGM) are known for their simple installation method that enhances shaft resistance and develops significant end-bearing capacity. Despite their effective performance and simple installation, limited research has focused on their behavior, particularly in determining bearing capacity, developing failure criteria, and interpreting load test results. In this study, 114 DGMs were installed across 23 different coastal sites with various lengths and full-scale tensile and compressive load tests were performed on them. To analyze their behavior, eight common failure criteria for deep foundations were used to interpret their bearing capacity. The results revealed that the existing criteria often require engineering judgment and cannot consider the induced shaft resistance as well as the end-bearing during DGM installation, so they are inadequate for interpreting DGM load tests. To overcome these limitations, a new failure criterion was proposed based on the framework of the Davisson method. This new criterion calculates the ultimate load displacement as the sum of elastic shortening and displacement related to the full mobilization of shaft and tip resistance. The elastic shortening term was refined using a reduction factor of 0.4, determined through statistical analysis. Additionally, based on the statistical analysis of ultimate load displacements, the displacement corresponding to failure in DGM was proposed as 15% of its diameter. Regarding the installation method of DGM, the load transfer mechanism shows that the share of end-bearing in the induced total bearing capacity is 25%.
Fakharnia et al. (Sun,) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: