A cavity expansion theory-based hyperbolic model for the pull-out force of a compaction-grouted soil nail

Abstract

Compared with conventional soil nails, the soil nail with grout bulbs (compaction-grouted soil nail) exhibits better performance in soil. In this study, a hyperbolic relationship was used to describe the relationship between pull-out stress (pull-out force divided by the cross-sectional area of a grout bulb) and displacement, in which the initial compressive modulus and ultimate compressive strength are the key factors that need to be determined in advance. In this case, the stress-strain behaviour of the soil around the grout bulb was investigated based on cavity expansion theory during compaction grouting and pull-out processes, and the initial compressive modulus with a compaction effect and the ultimate compressive strength were then quantified. Therefore, a cavity expansion theory-based hyperbolic model for the pull-out force of a compaction-grouted soil nail was proposed, in which the contribution of compaction grouting to the pull-out force was theoretically quantified. The proposed pull-out force model that combines the hyperbolic relationship and cavity expansion theory is simple and has high accuracy and will be useful for the design of the new soil nail with grout bulbs.