68th Canadian Geotechnical Conference and 7th Canadian Permafrost Conference

EVALUATION OF PREDICTION ACCURACY OF ULTIMATE BOND STRENGTH OF SOIL NAILS BY THE EFFECTIVE STRESS METHOD

Session: Foundations III / Fondations III

Peiyuan Lin, Ryerson University (Canada)
Richard Bathurst, Royal Military College of Canada (Canada)
Jinyuan Liu, Ryerson University (Canada)

This paper presents a statistical evaluation of the accuracy in predicting the ultimate bond strength of soil nails using the effective stress method (ESM). A total of 113 data points from field nail pullout tests taken to failure in Hong Kong were collected from the literature. After removing outliers, the data were used to estimate the accuracy of the current ESM. Based on the available data, the current ESM pullout model is found to be excessively conservative (on average) by a factor of three or more and the spread in prediction accuracy is large. In addition, the accuracy of the current model for prediction of nail bond strength is shown to be dependent on the magnitude of predicted ultimate bond strength. This undesirable dependency is traced to a strong correlation between model accuracy and vertical effective stress computed at the elevation of the soil nail anchor embedment length.