A modified lift-off test for restressing anchors of a rehabilitated landslide slope

This study proposed a modified lift-off test that enables evaluation of the anchoring condition (anchored capacity or creep ratio) during the investigation of the residual anchor load and facilitates the restressing of anchors. To verify the applicability of the proposed measure in practice, a case study of the rehabilitated landslide slope of the T16 support tower of the Taipei Maokong Gondola System was conducted, a two-stage procedure that simultaneously facilitated the investigation and rehabilitation of an anchored slope with load loss. Results of an investigation of the residual load acting on 619 anchors indicated that the average load loss of the anchors was approximately 36% compared with the design load. In conventional design, approximately 223 extra anchors must be installed in the study area. However, the corresponding number in the proposed measure is about one-fifth the number of anchors required in the conventional approach. This paper emphasizes the merit of using the modified lift-off test in reducing construction time and construction costs in slope rehabilitation. Furthermore, the proposed rehabilitation measure adopted in this study did not involve adding many concrete structures to the original anchored slope. Thus, these measures are environmentally friendly and contribute to sustainable development.