I-40 along the Cumberland Escarpment Highway Instability, Historic Reviews, and Remedial Concepts

摘要

The eastern Cumberland Plateau Escarpment, separating the Cumberland Plateau and the Valley and Ridge Physiographic Provinces, has a record of hampering highway construction in central East Tennessee, due to a combination of steep natural slopes, thick accumulations of colluvium, and the presence of swelling clay from the Pennington Formation. In that record is the 1968 construction failure of approximately 370 meters of eastbound Interstate Highway 40 embankment. Planned as an up to 43- meter high embankment across the Escarpment, the Tennessee Department of Transportation (TDOT) responded to the landslide and embankment failure through geometric modifications and slide mass drainage using dewatering wells and horizontal drains. Even with these mitigation measures and periodic installation of additional horizontal drains, movement of the slide mass has continued through the ensuing decades. Measurements in 2010 had shown displacement on the order of 25 millimeters per year, requiring annual resurfacing of the pavement. Interstate Highway 40 (I-40) is a heavily-traveled, east-west interstate through the mid-section of the United States. Traffic safety concerns with a traffic-disruption threat led TDOT to request a detailed review of the available project documentation by Golder Associates Inc. Since the initial slide, limited topographic, geologic, and geotechnical data have been gathered and assimilated for evaluation of the slide. As a result of Golder’s review, additional slope inclinometers and automated vibrating-wire piezometers were installed to better define the conditions and their variation with time. A limited laboratory testing program was conducted for evaluating potential remediation options. Installation of a system of dewatering wells and horizontal drainage was initiated in late 2011 in an effort to mitigate further displacement. Implementation of these drainage measures was still underway at the time of publication. This paper presents the historical background, results from the first year of slope and groundwater monitoring, dewatering program, and feasible remediation options available to TDOT in order to improve the margin of safety on this career-spanning slope failure.