Study On Some Problems Of Maintenance And Repair In Undersea Tunnel

Xiamen undersea tunnel is the first undersea tunnel built up in domestic. Geological environment, load model and design theory of the undersea tunnel have different key technologies to general mountain tunnels. The specificity of the undersea tunnel brings some new problems on the tunnel maintenance to us, but in usual maintenance and repair of tunnel, they will not be considered as specialized problems. Forasmuch, considering the design and construction experience of the Xiamen XiangAn undersea tunnel engineering, intensive studies and systematic analysis are made on the inspection method, the inspection frequency and the detection technology of the undersea tunnel, and the undersea tunnel diseases classification index, and the clearance displacement management reference of the undersea tunnel, and the long-term monitoring system of the undersea tunnel. Some studies are rare in domestic in this dissertation, and these achievements in research can be used directly on the maintenance of Xianmen XiangAn undersea tunnel, and they can also give references on the other subsea tunnel in domestic. The major work of this research is summarized as follows:1. The inspection system of the undersea tunnel was established and the inspection Contents was ascertained, with references general road tunnels inspection system. This paper investigates all kinds of inspection methods, inspection frequency and the detection technologies on domestic and international tunnel, analogy analysis shows that the suitable detection techniques are in the order of ground penetrating radar, infrared thermography, multispectral analysis, ultrasonic method.2. 3D FEM is applied to study abnormal characteristic of undersea tunnel when there are cavities behind the lining and lining deficiencies of thickness. A quantized decision standard was given according to effects on the structure inner force and fracture distribution of the subsea tunnel due to the abnormal. So, this study puts forward specific index for the disease classification of the undersea tunnel.3. Based on the state equation of generalized Kelvin constitutive model, a tunnel displacement analysis expression with the variable of time was derived, considering the time effect of rock mass rheology and space effect of construction excavation. This paper gives a prediction analysis on the displacement due to rock mass rheology of Xianmen undersea tunnel second lining according to the displacement data of 120 monitoring sections.4. Some sections of abnormal displacement were found according to prediction analysis in the undersea tunnel. Hereby, this paper puts forward proposal monitoring sections and monitoring contents. With the finite difference program and viscoelasto-plastic constitutive model of rock mass, rheological numerical analysis on these sections of the subsea tunnel were made, and their time—displacement curves of lining were gained also. A clearance displacement management reference value was given according to the results of the numerical simulation and theoretical analysis, and this offers a theory basis for the clearance displacement management of long-term monitoring.5. Depend on the statistical analysis result of lining crack in more than 50 tunnels at home and abroad, this paper puts forward that the major crack area of lining in the undersea tunnel is arch crown, and the secondary crack area is hance and side wall. 2D finite element method and fracture mechanics are applied to calculate the stress intensity factors of different location, different width and depth lining cracks. Stabilization crack depth ratios have been obtained according to crack stability, and then quantized index were given for safety evaluations of the undersea tunnel crack lining.6. A perfect monitoring system have been built on the undersea tunnel, and vibrating-spring sensors and fibre-optical grating sensors are built to network separately in this system, the monitoring data will be transformed to the centre control room of the undersea tunnel, and then all data can be gained automatically in long-distance. Artificial neural network theory and theory of probability are applied to build up a long-term monitoring safety evaluation model of the undersea tunnel base on BP network according the character of long-term monitoring data, this model can make safety evaluations on the undersea tunnel according to long-term monitoring data.