Research On The Mechanism And Construction Techniques Of Interaction For Adjacent Tunneling Preformed By Shield

For adjacent tunneling driven by shield, compared to ordinary shield tunneling in intact soil strata, more difficulties and complexities are encountered in the process of construction. Based on the project of Pudian Road-Zhangyang Road tunnel section in Metro Line 4 (crossing Metro Line 2) and the project of tunnel between Qibao and Jiuting in Metro line 9, this dissertation deals with the discussion on the mechanism of interaction for adjacent tunneling preformed by shield, together with temporal and space effect, and further analyzes the displacement of the strata and existing tunnel caused by adjacent excavation to achieve the variation law, based on which the sensitivity study of influence parameters is performed. During the research, the method of a combination of analytical solution, elastic or elasto-plastic numerical simulation and field measurement is adopted.On the basis of the research and engineering practice mentioned above, the author puts forward technical measures for reducing the disturbance due to adjacent excavation such as tunneling method of area division and control, optimized control of sensitive parameters in overlapping zone, feedback construction based on monitoring of electronic level bar and advanced strengthening of the soil and stiffening of the existing tunnel. These measures are to ensure a successful excavation and the normal operation of existing tunnels. This dissertation is of reference value and practical significance for utilization of intensive deep underground space as well as similar projects.Main achievements from the research are as follows:1. Interaction pattern of shield machine, soil and existing tunnel during adjacent tunneling is analyzed. Space effect characterized by below-above relationship and distance and angle between shield machine and existing tunnel is introduced. The adjacence of shield tunneling is modified. Temporal effect based on different stages of shield tunneling is put forward.2. Major influence parameters for adjacent shield tunneling are listed. Taking existing tunnels into consideration, calculation formula of the face pressure is illustrated and calculation formula of side friction is modified. Calculation method of ground loss due to deviation rectification and curvature tunneling is discussed.3. Employing both Mindlin Solution and Bobet Method at one time to analyze the disturbed displacement field for shield tunneling, a superposition rule of conjoint analysis of additional stress and ground loss is put forward. Affects of spatial parameters on adjacent shield tunneling are discussed.4. Patterns and magnitude of influence on the existing tunnel caused by side friction, face pressure and rectification load are compared. Range of plastic ring due to side friction is analyzed. Deformation of existing tunnel above the excavation in main working status is calculated.5. Based on field simulation tunneling and real cross engineering (above or below), sensitivity of major influence parameters are analyzed, thus achieving the ratio of head, side and subsequent influence on the deformation of existing tunnel.6. Techniques for disturbance control such as tunneling method of area division and control, feedback construction based on monitoring of electronic level bar and advanced strengthening of the soil and stiffening of the existing tunnel are introduced. These measures should be prudently compared and optimized according to actual condition encountered in different project to make adjacent tunnel engineering economic, safe and fast.