Design Characteristics of Near-Surface Rock Formations: Fid-Bau Portal

Design Characteristics of Near-Surface Rock Formations

D. H. Yardley

The project site, the main campus of the University of Minnesota, is underlain by a flat-lying competent limestone and under that lies easily excavated sandstone. The accessibility of the limestone provides a unique opportunity to obtain important fundamental and engineering information on the structural behavior of a jointed and bedded rock mass as excavation of a chamber proceeds beneath it. An excavation size of 50' wide x 100' long x 8' high is planned, and instrumentation is installed from the surface and from underground pilot drifts along the test room centerlines. Some other important aspects of the project are: (1) the development of a spray-grouting technique for in-place hardening of friable sandstone walls in rooms or tunnels; (2) the preparation of a design approach for cavern roofs in jointed and laminated rocks; and (3) encouraging the utilization of research results in general practice and demonstrating the potential of underground construction in an urban environment.