Uplift behavior of shaft anchors in silty sand in Taipei Basin

Abstract

Shaft anchors are commonly used in geotechnical engineering. They can be categorized into several types; however, the anchorage behaviors of the anchors are not well known. To determine the comprehensive behavior of straight shaft anchors, a series of triaxial tests were performed on silty sand to determine the parameters for a numerical model. The model was employed in the FLAC^2D numerical program to elucidate the uplift behavior of various frictional anchors in silty soil in Taipei Basin. To enhance the applicability of the numerical analyses, the field test results were compared with those of the numerical analyses. The analysis results indicate that the friction stress along the fixed end of the anchor with a long fixed length exhibits progressive yielding not only for a tension anchor but also for a compression anchor. The progressive yielding behavior can be eliminated using a compound anchor because of the upward and downward transfer of load within the anchor body from the anchorage point. Therefore, a compound anchor can generate a higher anchorage capacity than others. Because the calculated load–displacement curves of the numerical anchors were close to those measured in the field tests, the results of the numerical study and field anchor tests were used to establish the relationship between the total length and the anchorage capacity of frictional anchors in silty sand.

Keywords:

• anchors
• numerical analyses
• progressive yielding
• silty sand

Acknowledgments

The authors would like to thank the National Science Council of the Republic of China, Taiwan, for financially supporting this research under Contract No. NSC 99-2628-E-324-005. The authors also appreciate the Pao-Li Foundation Company for its assistance in the construction and testing of field anchors.