Mechanical properties and analytic solutions of prestressed linings with unbonded annular anchors under internal water loading

摘要

Concrete linings actively prestressed by posttensioning un-bonded annular anchors provide a sound solution to problems of pressure tunnels such as an inadequate overburden depth or adverse surrounding rock conditions. To further explore the mechanism of mutual action among the annular anchor, concrete lining and surrounding rock, a new large-scale in-situ loading test is proposed and carried out at a 6.8-metre diameter water conveyance tunnel in Jilin, China, in which case the internal water pressure is applied by an annular flat jack. Variation in the tension of the annular anchor and the characteristics of prestress redistribution in the lining during posttensioning the tendon and application of the internal water load are revealed. Furthermore, analytic solutions to the lining stress and bending moment induced by annular anchors and internal water pressure are proposed, which are verified by the field test results.