Experimental and Analytical Study of Jacking Load during Microtunneling Gongbei Tunnel Pipe Roof

Abstract

This paper presents a case study on the jacking load during the installation of Gongbei tunnel pipe roof using microtunneling. The pipe roof, consisting of 36 pieces of 1,620-mm-diameter steel pipes along a curved alignment, provides the preexcavation support for the Gongbei tunnel, which has a cross-sectional area of 338 m2 and a length of 255 m. The design jacking load was compared with the field measurement, and the difference was investigated. The equation for estimating the face penetration thrust during the slurry type microtunneling was recommended, and a formulation for predicting the total jacking load of the segmented steel pipe along the curved alignment was developed on the basis of the force equilibrium analysis. The unit side frictional resistance and the frictional coefficient of the steel pipes were derived on the basis of the statistical analysis of the field data. The findings from this paper can provide guidance for the design of the jacking load during microtunneling operations for the installation of steel utility pipelines and pipe roofs.