The 4.7m diameter Lovat EPBM working on the sewer upgrade project in Belfast was more than 156m into its second, 2.2km long drive by late last month, buildings 12 rings on average per shift.

JV contractor of Morgan Est/ Farrans (Construction) is installing the pit bottom crossing that will enable advance rates to increase to 18-19 rings per shift, said Lovat.

Best daily and weekly production rates for the mixed face EPBM have been 19 rings and 138 rings, respectively. The rings are 1.2m long and on the second drive so far the average mining time has been 20 minutes and the build time is 15 minutes.

Geology along the second drive comprises boulder clay in the early part and then a mix of clay, sandstone and malone sand. It is expected that dolerite intrusions may also be met, which would require a tool change from rippers to disc cutters.