Time-dependent deformation of small tunnels—I. Experimental facilities

Abstract Several processes contribute to the time-dependent deformation of underground openings. Because of the importance of these deformations in the design of support systems and the evaluation of the stability of the opening, a research program has been initiated to investigate the relative importance of these time-dependent processes. For this purpose, an apparatus has been constructed to test small tunnels in the laboratory. This first part of a series of publications provides a general description of the project; it describes the test system, the data processing and presentation, the material (coal), which has been used to represent a rock mass with time-dependent strength and deformation properties, the sampling procedure, the sample preparation, and the instrumentation of this naturally discontinuous medium. A comparison of the applied loading history with the loading history actually encountered in tunnelling is presented. The load level during testing was selected to represent the conditions of a tunnel at large depth or in weak rock.