Application Technology Of Layout And Correction Control Of Universal Segments For Shield Tunnels In Soft Soil And Construction Monitoring Research

The universal segments can adopt a certain amount of wedge ring lining,which can rotate and assemble,to the whole tunnel construction.The segments formation is suitable for a straight line,turn left curve,turn right curve,space curve,and various conditions.Only a set of mould can achieve any type of tunnel using this form of tunneling lining that can be lower cost and more suitable for curved segments of designed tunnel axis.However,as more assembly point of the universal segments and more complex system,inappropriate point selection cannot meet to fit designed tunnel axis,meanwhile,it will lead to adverse consequence,such as deviation of shield machine,and segments broken.It is impossible for the shield machine to completely fit the designed axis during the shield construction.According to the actual site conditions,it need dynamically adjust the shield machine of posture and segments composition to control the deviation of the segments axis and designed tunnel axis in a certain range.Shield machine propulsion process will directly affect the segment assemble.If the shield machine promote is unreasonable,it will lead to the segments cannot be successfully assembled.Hence,it is important to research the segments composition,correction and propulsion process.As a coastal city,Ningbo area is the characteristic of a unique soft soil formulation,with soil moisture,high sensitivity,low intensity,it will lead the shield tunneling and shield machine to be floating in the shield construction.Hence,it put forward higher requirements to the universal segments correction and propulsion control.At present,shield construction management and monitoring method of the universal segments is imperfect,engineering application is not sufficient,the research of construction management and monitoring of shield tunnel in soft ground is little,hence,it is more important to research on the above problems in the application of soft soil technology and shield construction management.Combined with the needs of construction technology and management of Ningbo subway tunnel shield and the characteristics of Ningbo formations,according to Ningbo Rail Transit Line 1 and Line 2 as the project engineering background,this paper explore comprehensively the shield tunnel construction in soft soil formations from correction control theory of shield segments,point selection,jack stroke based on the gap of the shield as the control indicator with known point of universal segments,respectively.The main contents are as follows:(1)Through analyzing the relationship of designed tunnel axis,shield machine axis and tunnel axis,and the solution of special coordinates,this paper put forward to corrective curves according to different designed axis and different initial positions of shield machines,then it provide the foundation for the shield machine to correct the deviation control.(2)Through the comparative analysis of domestic composition model of universal segments,the core algorithm for the integrated method of gap of shield tail,stroke difference and segments softness is established.Then,intelligence of point selection can be achieved.(3)In order to guarantee the segments whose point has already been calculated can be successfully installed,based on the spacial relations of shield machine and segments during the process of advancing,the calculation model of the gap change of shield tail is established.By calculating the gap change of the shield tail caused by Jack stroke difference of the shield machine as well as the position of the segment point,an estimation method for Jack stroke travelled range is proposed under the allowed gap of the shield tail.Then,according to the estimation results,the shield excavation process is well controlled.The excavation process can be controlled based on the result of calculation,then,intelligence of process control can be achieved.(4)This paper provides the key parameters of shield tunneling construction and management monitoring,such as the shield-tail gap,the deviation between the segment and the designed axis,the angle between the tube-plane normal and the axis of the shield machine.Meanwhile,it summes up the key parameters of the classification index,and laies the foundation to achieve fine management of the shield construction.(5)The applicability of automatic layout correction system in the soft formation is studied.The effective method of automatic layout correction system in the soft soil formation is established.The result shows that the calculate results are reliable,if it calculates and composites every ring of promotion.However,automatic composition correction system cannot consider the influence of formation conditions on the shield construction.Through comparing the results of automatic ring selection system and self-developed automatic selection program,the scientific calculation principle of automatic selection program is verified.As a coastal city,Ningbo area is the characteristic of a unique soft soil formulation,with soil moisture,high sensitivity,low intensity,and give the great challenges to the error correction control.Hence,it will improve the efficiency of shield construction,reduce the work intensity of engineering and technical personnel,and reduce blindness of dependence on past experience by using computer technology to achieve the section composition,correction and propulsion control of shield tunneling construction.