Abstract: This study focuses on improving stress distribution and preventing crack formation during the tensioning process. To achieve this, we conducted full-scale model test and proposed a tension sequence and quality control indexes. Initially, we calculated the friction coefficient based on steel strand friction test. Subsequently, we applied the tension sequence and quality control indexes using an automated tension system. To monitor stress changes, we used elastomagnetic sensors for the steel strand, and strain gauges for the lining concrete. Field tensile tests yield the following key findings: 1) The steel strand experiences a prestress loss of approximately 16.3%. However, by utilizing double-layered steel strands, we ensure a highly effective prestress in practical applications. 2) Applying the proposed tension sequence in the anchorage slots results in the lining concrete achieving a relatively uniform annular compressive stress, with an average compressive stress of -10.9 MPa. 3) The three control indexes we recommend can be quantitatively managed, and when combined with automated tension technology, they effectively guarantee the quality of tension.

Key words: unbonded circular anchor, prestressed lining, sequential tensioning, quality control, full-scale model test