Title: Location of Sub-Asphalt Voids Under US-34 After Severe Flooding using Nondestructive Evaluation Techniques

摘要

In September of 2013, the Front Range area of Colorado experienced a series of extreme rain events, which resulted in severe flooding in a number of mountain canyons. These flooded canyons included the section of US-34 west of Loveland known as "The Narrows". The section of US-34 in The Narrows was previously washed out by a major flood in 1976, and rebuilt using an anchored retaining wall system protected by riprap/boulders on the river side. During the flooding of 2013, the riprap and boulders were washed away and portions of the retaining wall were undermined by the water, resulting in washing away of the wall backfill from underneath and collapsing the asphalt pavement. This paper presents the results of an investigation conducted on the visually intact sections of the roadway to determine if there were any areas of undermining that did NOT result in visible pavement collapses. The investigation was carried out primarily with the Ground Penetrating Radar (GPR) test method, with additional information from other Nondestructive Evaluation (NDE) methods. The roadway was scanned from the surface, with no drilling or other intrusive sampling required. The results of the investigation showed one significant area of apparently intact pavement that had a major void underneath. The paper will present the typical testing done, and overview of the test methods, sample data showing both sound and voided areas, and photographs of the roadway and voided area after excavation.