Creep behavior of soil nails in the high-PI clay

Creep behavior in soils is closely related to the stress level. In contrast, geotechnical engineering circular no. 7—soil nail walls (GEC#7) associate the creep behavior of soil nail systems with the presence of high-plasticity (PI) clays solely, regardless of the load level. Soil nail pullout tests are performed at the National Geotechnical Experimentation Site (NGES) of Texas A&M University to study the creep behavior of soil nails in high-PI clays. The data fits very well with a power-law model. The creep failure criterion from GEC#7 could be readily converted to the residual movement criterion in the model, which corresponds to the load level slightly higher than 80% of the ultimate load in this study. It verifies that the design practice by the Texas Department of Transportation (TxDOT) is working to control the long-term deformation by creep in high-PI clays by restricting the service load to one-third of the ultimate load. Besides, results from this research come with other recommendations to reduce long-term deformation by creep in high-PI clays during the lifetime of soil nails by applying the cycle and the preloading in the construction.