Temperature monitoring of frozen ground during construction of Gascoigne Wood drifts, Selby Mine

The paper describes the development and operation of a detailed temperature monitoring programme used as a control on the excavation process through a complex zone of frozen ground during the drivage of the twin surface drifts at the Gascoigne Wood Mine, Selby, UK. To ensure a complete interlock between grouted and frozen zones at the base of the Lower Magnesian Limestone formation special temperature sensing probes were devised for the exploration of the ice-wall profile through holes drilled from the existing drift faces some 30m away from the ice. The results obtained from monitoring with both exploratory and resident probes had a significant impact on the overall programme of drift construction, by changing the sequence in which the drifts were advanced through the frozen strata. Once the drivage had been extended through and beyond the frozen zone further sets of temperature probes were installed in order to monitor the controlled ice thawing phase. As the ice-wall retreated so the backwall grouting in the Lower Magnesian Limestone and Basal Sands was carried out in stages to a timetable based on the temperature measurements. The design, construction, deployment and monitoring of the various systems of temperature probes are discussed together with the results obtained over a total period of some 14 months.