STUDY OF REASONABLE SUPPORT PARAMETER FOR LARGE-SCALE SHIELD SHAFT IN SOFT SOIL AREA

It is a technical difficulty to control the deformation and the stress condition of the structure of large-scale shield shaft in over-river shield tunnel project.This case study how to deal with the excavation of Jiangbei shield shaft of Weisan Road over-river tunnel at Nanjing City.Use four-factor at three-level orthogonal array experimental design method to proceed multifactor system analysis,studying the effect rule of deformation and stress of the whole support structure caused by the change of the thickness of ring beams,retaining wall,lining wall and bracings.The interaction relationships between each support component are obtained and analyzed;and through the quantification analysis of the total cost,a design scheme of the minimum total material cost is proposed which has been conditional on the security of the whole structure.This study indicates that:using orthogonal experimental design method to decide the reasonable support parameters of the shield shaft can minimize the calculation,obtain the optimal combination of the support parameters with the confirmation of stability,and achieve the best technical and economical result.