Numerical Study for Compaction-Grouted Soil Nails with Multiple Grout Bulbs

A finite-element model was adopted to numerically simulate compaction-grouted soil nails with multiple grout bulbs. The numerical model was first verified by the corresponding experimental results. Then a series of numerical simulations were carried out to investigate the pull-out behavior of compaction-grouted soil nails with multiple grout bulbs. Numerical results show that the pull-out force increases with the increasing diameter of the grout bulb and the spacing between the grout bulbs. Furthermore, the pull-out displacement at failure of the soil nail decreases for the bigger grout bulb. Soil nails with larger back-end and smaller front-end grout bulbs experience the higher peak pull-out force and larger pull-out displacement at failure. Two types of failure surfaces were found for the soil nails with a double-grouted bulb, and those with a curved failure surface gave the largest pull-out displacement at failure. It indicates that the grouting point placed at the end of the nail rod is more preferable in field application. An equal spacing and grout bulb diameter can help to maximize the performance of a compaction-grouted soil nail with multiple grout bulbs.