Underground Research Laboratory room 209 instrument array. Vol. 1,2

An in situ excavation response test was conducted at the 240 Level of the Underground Research Laboratory (URL). The test was carried out in conjunction with the drill-and-blast excavation of a near-circular tunnel (Room 209), about 3.5 m in diameter. The tunnel was excavated through a tunnel axis. Three modelling groups made predictions of the response of the rock mass and hydraulic behaviour of the water-bearing fracture to excavation. The tunnel was excavated in two stages, a pilot tunnel followed by a slash, providing two complete sets of response measurements. Careful excavation was carried out to ensure the excavation shape after each blast round agreed closely with the planned shape incorporated in the numerical models. Instrumentation installed before the tunnel was extended monitored the complete strain tensor at eight locations around the tunnel, radial displacements and piezometric pressures at nine locations in the fracture. As well, tunnel convergence, water flows from the fracture, and hydraulic conductivity of the fracture at nine locations, were measured after each excavation step. The final tunnel profiles were accurately surveyed, and the geology was mapped in detail. The results are presented in this report for comparison with the modellers' predictions (reported in AECL--9566-2). Some preliminary conclusions and recommendations regarding the field testing are presented