Convergence measurements in a 300 m deep borehole in rock salt

An evaluation is presented of convergence measurements in a 300 m deep borehole in rock salt. The measured convergence is compared to the normalized convergence based on an analytical solution. Measurements endorse the assumptions on which the analytical solution has been based. With the aid of this analytical solution the ambient rock pressure at the locations of the measurements is determined. The derived pressures and the corresponding depth below the 750 m level are 20.3 MPa at -300 m, 15.4 MPa at -200 m and 13.3 MPa at -100 m. The measurements, normalized in order to account for the influence of the diameter and for the difference in depth, show good correspondence with former measurements on selected cavities in rock salt. (author). 6 refs.; 17 figs.; 3 tabs