Prestress Model And Prototype Test On The Ultra-diameter PCCP In Mid-route Of South-to-North Water Diversion Project

Under the background of the Mid-route of South-to-North Water Diversion (MSNWD) project in China, some research works are done for the consideration of the stiffness and behavior of the wire of a PCCP. A new finite element model, called wire-wrapping model, is proposed to simulate the prestressing of a PCCP. Some prototype tests on the embedded PCCP with an ultra-diameter of 4m used in the MSNWD project are conducted. On the basis of the response patterns of the PCCP found in the prototype tests mention above, a new model, called wire-breaking model, is proposed to simulate the process of breaking wire. The analysis of the pipe structure and the evaluation of the load-bearing capacity of the embedded PCCP are performed. The main contents and the innovative points are summarized as follows.1. A wire-wrapping model is proposed to simulate the process of wrapping wire for the prestressing of an embedded PCCP with an ultra-diameter. The wire-concrete core interaction and the contribution of the wire stiffness are taken into account in this model. The stress and deformation of the wire could be calculated correctly. The wire-wrapping model is applied to simulate the prestressing of an ultra-diameter embedded PCCP used in the MSNWD project. The results obtained using the wire-wrapping model are analyzed and compared with those obtained using current methods for its verification.2. Some prototype tests on the ultra-diameter embedded PCCP used in the MSNWD project are conducted for the first time. The load-bearing response patterns of the PCCP under loads are obtained. The new wire-breaking response patterns are also found, which exhibite the effects of breaking wire on the stress states of the unbroken wire and broken wire itself. A new concept called bonding-lost length is presented, which describes a certain length to develop again the bonding effect with the mortar when a wire breaks.3. On the basis of the response patterns of the PCCP found in the prototype tests mention above, a wire-breaking model is proposed to simulate the process of breaking wire for the un-prestressing of an embedded PCCP with an ultra-diameter. The bonding-lost length could be determined quantitatively in this model. The distribution of wire stress and gripping power are obtained. The mechanism the response when a wire breaks can be reflected by the wire-breaking model. The wire-breaking model is applied to simulate the process of breaking wire of an ultra-diameter embedded PCCP used in the MSNWD project. The results obtained using the wire-breaking model are analyzed and compared with those obtained from prototype tests for its verification.4. The wire-wrapping model and the wire-breaking model proposed in this dissertation are applied to simulate and analyze the processes of three-edge bearing tests and hydrostatic pressure tests of the ultra-diameter embedded PCCP used in the MSNWD project. Here, two kinds of PCCP are considered: the PCCP with and without broken wires. The load-bearing resoponses of PCCP are analyzed and the load-bearing capacity of PCCP is evaluated in this part. Finally, some significant engineering conclusions about the mechanism of pipe rupture are presented.