Performance Evaluation of Jacking Force Models for Tunnel Bore Conditions Characterisation

Since the ability of many available jacking force models to characterise the tunnel bore conditions is limited. A simple approach to characterise the tunnel bore conditions is proposed and applied to a case study where four sewer pipelines of the Shulin district sewer network in Taipei County, Taiwan were constructed to verify its validity. Four jacking force models are benchmarked in this study. Based upon the given soil properties and pipe dimensions as well as the pipe buried depth, the calculated normal contact pressure (σ′) from each model and the measured frictional stress (τ) in each baseline section are utilised for the back-analysis of the frictional coefficient (μavg). The μavg values outside the range of 0.1–0.3 recommended for lubricated drives can be ascribed to the increasing pipe friction resulting from the excessive pipe deviation or ground closure or the gravel formation not being long enough to establish lower face resistance. JMTA has indicated a further potential use in assessment of the interface performance during pipe-jacking works.