Study On Safety Evaluation And On-line Monitoring Of Un-bonded Circumferential Tendon Of Prestressed Tunnel Liner

Hydraulic tunnel is the most common type of diversion structures in hydraulicand hydroelectric engineering, mainly used for flood discharge, diversion and power,conveyance of water irrigation, excretion reserrvoir sediment, diversion etc. Thetunnel liner pre-stressed with circumferential un-bonded tendons as a new structurewas gradually applied to hydraulic tunnels recently. It is a new type of structure whichcan full play to the characteristics of prestressed. Which is suitable for the hydraulictunnel engineering with high water head, thin surrounding rock, and poor geologicalconditions. If the leakage took place, it may cause fatal accidents such as the damageof adjacent buildings or the failure of side slope. Up to now, prestressed concrete linerhas been used in a number of large hydraulic engineering in China, for instance, thehydropower tunnel of Ge Heyan hydroelectric power plant, Tian Shengqiaohydropower tunnel, Yellow River crossing tunnel of south-to-north water transferproject, as well as Xiao Langdi sediment tunnels and Liaoning Da Huofang reservoirwater conveyance tunnels. Compared with other structures, the tunnel linerpre-stressed with circumferential un-bonded tendons has many outstandingadvantages, but as a new structure the security and reliability restrict its generalapplication.Based on the first hydraulic tunnel of the liner pre-stressed with circumferentialun-bonded tendons Xiao Langdi sediment tunnels, analysis a lot monitoring data sinceJune1999in operation. Obtained the layout of monitoring sections, the analysismethod of monitoring data and the influencing factors of monitoring instrumentsaccording to this kind of structure. Also determined the running state, the structuresafety evaluation and the safety warning value of the tunnel liner pre-stressed withcircumferential un-bonded tendons during operation period. By the above analysisalso showed that: after operation more than ten years, on various environment, thetunnel liner pre-stressed with circumferential un-bonded tendons in Xiao Langdi didnot crack, leakage, the strand not fracture or relaxation, lining concrete most inpressured state. The structure of liner pre-stressed with circumferential un-bondedtendons is safe and reliable. Study on the safety evaluation of Xiao Langdiengineering, not only could verification the safety evaluation method, but also could provide guidance for the layout of monitoring instrument in similar projects. Providdefinite reference and data information to implementation safety evaluation in thestructure of liner pre-stressed with circumferential un-bonded tendons.