Pull out resistance of pressure grouted soil nails a cavity expansion approach

Abstract

Soil nailing is a well-proven technology for reinforcing natural and man-made slopes, newlineexcavations, retaining walls, and so on. Recently, pressure grouting in place of conventional gravity grouting has emerged as an effective method for improving the newlinepull-out shear resistance of soil nails. The pull-out shear resistance is influenced by newlineseveral factors; however due to the complex behaviour of soil and soil-grout interaction, newlinethe influence of all these parameters on the soil-nail pull-out behaviour was not well newlineunderstood. Studying the evolution of stress state and soil properties around the nail newlineduring the nail installation processes will aid to develop an appropriate method for newlinepredicting the final soil state (residual confining stress and soil properties) and thus to estimate unit skin resistance at the grout-soil interface. This may be possible with the aid of cavity expansion and contraction theories, as the installation stages and pull-out testing of pressure-grouted soil nails can be considered analogous to either a cylindrical cavity expansion or a contraction problem. newlineSince the existing cavity expansion and contraction solutions have some inherent newlinelimitations to apply for the analysis of pressure-grouted soil nails, the first objective of this research was to formulate a new cavity expansion and contraction solution newlineincorporating the non-linear soil response, applicable for both cavity creation and newlineexpansion problems in sand, which can predict the entire soil-state at any stage of newlineexpansion and subsequent contraction. These new analytical solutions developed for newlinesand were further extended to apply in unsaturated residual (cohesive-frictional) soils by integrating the effect of suction and different drainage conditions. The solution procedure was validated using well-documented pressuremeter test data in unsaturated residual soils. newline