Study On Influence Of DOT Shield Excavation On Overlapping Tunnel

In recent years, overlapping tunnels have emerged in facilitating the underground space utilization. In the construction of double-track tunnel through overlapping tunnel, the traditional single-tube shield construction has some limitations in the narrow and shallow buried underground space line. DOT shield can complete the double-track tunnel excavation without the underground construction of connecting passage. It has the advantage of saving underground space and construction costs and shortening the construction time. It will be widely used in the constructions of double-track tunnel. However, disturbance to the ground by DOT shield is different from the ordinary single-tube shield construction because of the special structure and construction technology. Therefore, the study on the DOT shield effect of the near formation of overlapping tunnels also the tunnels has the vital significance. In this paper, based on a construction of a double-track tunnel through overlapping tunnel, the difference between the effect to the near formation of overlapping tunnels and the tunnels of DOT shield and the traditional single-tube shield construction are analyzed comparatively by numerical simulation method. Also the influencing factors in the process of DOT shield overlapping construction are analyzed. It provide the basis reference for related projects in future.Firstly, the impacting mechanism and finite element theory of DOT shield are described. Based on a construction of a double-track tunnel through overlapping tunnel, the dynamic model of construction of single-tube single-truck tunnel, single-tube double-truck tunnel and DOT shield are established with ADINA finite element software. Soil deformation, surface displacement, overlapping tunnel stress and deformation characteristics caused by these three shield construction method are retrospective analyzed. The theoretical results of ingle-tube single-truck shield construction method are close to the measurement data which proves the validity of the model. The calculation results of these three shield construction method were compared, which showed that the effectiveness of the DOT shield construction method is the best. DOT shield has certain advantages on the reinforcement scope and control of shield construction.Secondly, discuss the influence law of surface subsidence and overlapping tunnel deformation due to the affecting factors of DOT shield such as construction speed, soil pressure, stratum loss caused by construction, clear distance and buried depth of the new and old tunnel, overlapping tunnel diameter and so on. The research can offer the reference for the design optimization and construction of the overlapping tunnel of DOT shield.Finally, based on the measures from the following four aspects: DOT shield technical control, reinforcing measures of tunnels and middle soil layers. DOT shield tunnel is proposed for designing construction and optimization the same project.