Performance analysis of utility tunneling data: A case study of pipe jacking in hard rock in Brittany, France

Abstract

The increasing demand for renewable energy is accompanied with an urgent need for new and improved infrastructures worldwide, which in turn will require a greater number of utility tunneling projects in rock. Mainly due to tighter safety regulations, hard rock pipe jacking is getting increasingly important in the utility tunneling industry. Based on the example of the 530 m long Landivisiau utility tunnel case study, we present the first comprehensive pipe jacking study in high strength metamorphic rocks. The procedures and associated challenges of data analysis of a small-diameter pipe jacking project are presented and discussed. The tunnel has an outer diameter of 2.2 m and was excavated in Variscan basement rocks of Brittany. The geotechnical conditions at Landivisiau were very heterogeneous and stronger than expected, comprising fresh to highly weathered, weak to very strong gneiss, granite and schist with an UCS of up to 185 MPa. The TBM achieved an average advance rate of 17.3 mm/min and an average penetration rate of 3.4 mm/rev. The advance and penetration rates of the TBM are compared with results obtained by recent force estimation and penetration models. This study was conducted to raise awareness about the importance of using geological and technical data, to cope with increasingly strict controls by local authorities and to provide a foundation for further analysis and use of data, especially with respect to future automated tunneling.