| Concrete-filled thin-walled steel tube is a kind of composite structure consisted of thin-walled steel tube filled with high-performance concrete. It is of high bearing capacity, better ductility and fire resistance. The concrete-filled thin-walled steel tube can be installed easily and work under harsh environment. Now they are mainly used in high buildings, arch bridges and other towering structure or construction under dynamic loading, but less used underground, such as all kinds of tunnels. The existing support in a tunnel, such as bolting, is wet, time-consuming and severely pollutionaL Steel support, taking U-section steel as example, can’t combine closely or work well with surrounding rocks, and is easy to occur lateral instability. Considering the mechanical properties, concrete-filled steel tube is thought to be helpful to make surrounding rocks more stable by itself, and meanwhile, it needs less steel and welding job. The construction speed can also be increased when it is used as tunnel support. Major achievements of the dissertation are as follows:1、Based on the existing theory, check formulas for bearing capacity of concrete-filled thin-walled steel tube support in a round tunnel is proposed in this paper.2、Five concrete-filled thin-walled steel tube supports are designed to be tested in a cable tunnel in Jinan. They are different in concrete-filled or not, thickness of tube and style of node, and they are also compared with grid steel frame in this tunnel. The testing results showed that, the concrete-filled thin-walled steel tube support can ensure the tunnel to be stable in a relatively short time. During testing period, all the concrete-filled thin-walled steel tubes performed elastic. The node structured by steel sleeve filled with cement performed flexible, and when the support is connected by this type of node, it is easier to deform. The maximum strain distributions were also obtained in experiment. The cost of support will be lower when using thinner steel tube.3、FBG(Fiber Bragg Grating) monitoring system has higher anti-interference capacity and is more accurate than old monitoring method. It can be used in testing work of underground structure. 4、FEA model of concrete-filled thin-walled steel tube support using ABAQUS was established, and the calculation result coincided well with experiment result. Coulomb-Friction model was adopted to imitate the interaction between concrete and steel tube, and the result was conservative followed by more close to testing result. So this FEA model can be promoted in similar work in the future. Error between FEA and experiment ranges less than15%. This model can be used in similar project in the future. |
PDF Full Text Request