The Kielder water scheme, currently under construction in north-east England, will consist of 32 km of tunnel to direct water from the Tyne to the wear and tees river valleys. The project, which is promoted by the Northumbrian water authority, involves excavation through sedimentary strata using 3.5 m-diameter tunnel boring machines. The tunnels division of the transport and road research laboratory (now the tunnels and underground pipes division) planned and implemented an observation programme during tunnel construction for the north wear drive, a portion of the Kielder tunnel system linking the river wear with a companion tunnel drive from the Derwent valley. The observations were performed with the assistance of Babtie, Shaw and Morton, the general engineering consultants for the Kielder water scheme. Detailed observations and measurements were taken in the first 1600 m of the north wear drive, where the tunnel was driven through approximately equal lengths of sandstone, limestone and mudstone. This paper summarises the structure and material properties of the in-situ rock in each of the principal lithologies and compares the observed ground conditions with the machine advance rates and rock support adopted during tunnelling. Attention is directed to the performance of the tunnel boring machine in light of the geological conditions, and improvements are suggested as an expedient to future machine excavation. In addition, the results of seismic scans, taken along the tunnel, are summarised and compared with detailed observations of the rock conditions. (Author/publisher)
Samenvatting