Use of Portable Seismic Property Analyzer to Assess Colorado's Hanging Lake Tunnel Liner

A survey of the condition of the tunnel liner in Hanging Lake Tunnel, near Glenwood Springs, Colorado, was performed with a handheld device, the portable seismic property analyzer (PSPA), within the framework of SHRP 2 Project R06G. The PSPA simultaneously applies two stress wave–based nondestructive testing (NDT) methods: the ultrasonic surface wave (USW) and the impact–echo (IE). The USW method can provide the average modulus as an indication of the quality of the concrete. The IE method can provide the thickness of the concrete liner or the depth of any reflector within the liner. The objective of this study was to evaluate the applicability of the PSPA to tunnel work and the performance of the IE and USW methods in estimating the thickness and evaluating the quality of the tunnel liner. For this purpose, several sections of the plenum of Hanging Lake Tunnel were tested. The selection of the testing areas was based on a visual inspection, infrared thermography, and the surface dielectric constant measured by other NDT methods. The results from this study demonstrated that the combination of the IE and USW results provided by the PSPA enhanced the effectiveness of the two methods in detecting and locating the defective areas within the tunnel liner. No additional time was needed to collect the data.