DIAGNOSIS OF TUNNEL ROOF STABILITY WITH A ROBOTIC SENSOR TEST-BED

An integrated method of roof inspection is proposed that will assist r isk assessment in respect of the stability of an existing underground excavation. Inspection is undertaken by an automated system-the roboti c sensor test bed-that comprises sensors on a mechanized arm together with control and data-processing software. The system, which is curren tly undergoing development and testing, employs a sonic/ultrasonic wav e-response sensor, a laser surface profiler and a surface-temperature sensor for data acquisition. The sensors are mounted on an articulated robotic manipulator to enable a remote-controlled or a fully automate d diagnosis to be performed. A number of sonic/ultrasonic tests were c onducted in the laboratory and in the field. A high-energy ultrasonic transducer and an impact device were used in the laboratory to induce vibration in a range of materials in both the ultrasonic and the sonic frequency ranges. The depths to fractures in rock slabs were found to be inversely related to the resonance frequencies measured, with acce ptable agreement between estimated and actual dimensions. In undergrou nd field tests it was established that loose and solid rock on the sur face of an excavation could be clearly distinguished on the basis of t heir different wave responses. The automated laser profiler measures t he surface geometry of the tunnel. Different scanning methods are bein g developed to achieve the fastest and most precise measurement and to provide pertinent information on rock joints and major fractures.