Underground excavations in rock salt.

An historical review of the geotechnical behaviour of the Northwich Rock Salt is presented as a forerunner to a numerical modelling analysis of the current stability of the Winsford salt mine, Cheshire. Extensive laboratory and in situ tests have been historically undertaken by the mine to characterise the strength and stiffness behaviour of the rock salt. Recent proposals to store waste within the Bostock No. 5 panel of the mine have lead to increasing concerns as to the current stability of the workings, as well as to the long term stability of the mine. This present study uses the wealth of geotechnical data to assess the current mine stability using numerical modelling techniques and validates the results against in situ roof to floor convergence data. The results indicate that the mine structures are stable. Convergence simulation using the numerical model compare favourably with the in situ monitoring data allowing greater con.dence to be placed in future predictions