Research On Key Technology Of Shield Method In Constructing Thermal Power Tunnel

With the rapid development of China’s urbanization construction and national economy, central heating system, which has advantages in energy saving, hygiene and environmental protection, isfully developed in Beijing. To solve safety and disorder problems of underground pipelines, it’s necessary to construct thermal power tunnels. Shield method has been widely applied in the construction of subway tunnels and municipal pipelines at home and abroad, but is rarely applied in the construction of thermal power tunnels.The thesisrelies on the project "Research on key technologies of thermal shield construction methods applied in thermal power tunnels" andpractical No. 11, No.18, No.24 and No.26 shaft construction projects of thermal power pipelines, which are installed in interval from Power Plant to Qingnian Road (from Zhongba Central Road to the second channel of Beijing Capital Airport) and interval from Beijing Capital Airport to Wenyuhe Road of Northeast Thermoelectric CenterMatching NetworkNorth Line. On the basis of field monitoring data and characteristics of shield tunnel construction, as well as adopting stratum structure analytic model, the thesis uses program FLAC 3D, which solves underground engineering problems professionally, to mainly do research on following contents:(1)Research on stress and deformation characteristics of different parts of tunnel based on shaft construction ahead of tunnel excavation (Shaft-Tunnel) method under two construction conditions, as well as analyze the influence scope of shield tunnel excavation.(2)Analyze stress and deformation characteristics of different parts of tunnel based on tunnel excavation followed by shaft construction (Tunnel-Shaft) method under two construction conditions.(3)Analyze deformation and stress characteristics of different construction conditions based on field monitoring data and numerical simulation results.(4)Analyze stress and deformation characteristics of surrounding rocks, shotcrete and shield tunnel segments under four different reinforcing schemesduring removinginner segments of shafts.The main results are as follows:(1)For Shaft-Tunnel scheme, the stress and deformation characteristics of tunnel by constructing the second lining early are better than the deformation of tunnel by constructing the second lining late, and the influence scope of shield tunnel excavation is also smaller than that by constructing the second lining late.(2)For two different construction methods in Tunnel-Shaft scheme, the stress and deformation characteristics are better for constructing fender piles early.(3)Considering construction difficulties of Shaft-Tunnel and Tunnel-Shaft methods, and numerical simulation results, a rational construction scheme is proposedin order to provide guidance for similar projects. Shaft-Tunnel, constructing the second lining early is suggested when the construction period is long. As for the condition when the construction period is short, the rational combination of Shaft-Tunnel, constructing the second lining early, Shaft-Tunnel, constructing the second lining late and Tunnel-Shaft, constructing fender piles early is suggested, and Tunnel-Shaft, constructing fender piles late should be avoided.(4)When the removal of shield tunnel segments. The scheme of consolidating at a length of 8 ring segments is suggested.