Research On The Key Technology And Experience Of Shallow Tunneling Method Crossing Under The Existing Subway Tunnel

This thesis is based on extensive research on scientific and technical literature both in China and abroad. According to former engineering experience and my effort, technical measures and management methods for tunnel passing from the bottom of the existing subway was set up to form the core technique for such problem. Combined with the project of subway line 5 passing from the bottom of existing subway line 2 in Beijing, this kind of new line passing through bottom the existing line was mainly studied in this paper. From the view of design and construct using shallow tunnel construction method, the dynamic response of the existing subway, the optimal distance between the new subway and existing subway, settlement control of the existing line and the recover of the existing line after new line construction were also studied in detail.According to the research above, a series of useful achievement both for theories and practice are shown below.(1) Based on former study, the key problem: interaction and control target: engineering safety for new subway passing from the bottom of the existing line is studied. According to different aims in different construction stages, 5 main technical points are summarized and technical system for such passing project is formed. In this thesis studies are carried out respectively for each different technical points.(2) The relationship between strata deformation, existing structure and rail track as well as probable failure types for them are studied to build failure modes for such passing project. In this passing project control standards can be made by the different construction step of the new line as well as the settlement control standard for the existing line. During new line construction it is necessary to adopt whole process inspects to make sure the safety of the project. The safety of the existing structure can be ensured by new line build.(3) Track vibration mechanics and vehicles-track coupling dynamic mechanics are used to study the influence of the existing line vehicle to the new line and the influence of the new line to the existing line in the way of existing line speed and safety. Optimal distance between the existing line and the new line are studied also. These can be of great meanings to such passing projects.(4) The magnitude of displacement in each construction step is analyzed using energy method. Settlement control standards of each construction step for the existing line is made. According to the characters of the new line and operation requirements for the existing line, monitoring measures are formed. These analyses and feed back measures are made to ensure the safety of existing structure.(5) Grouting used in subway for existing line life up is studied. The research of grouting parameter and grouting method can offer guidance to this kind of project.(6) The conclusion put forward in this thesis is proved right in the project of subwayline 5 Chong Wenmen station passing from the bottom of the existing line.