Perennial Infiltration-Induced Instability of Interstate 70 Embankment West of the Eisenhower/Johnson Memorial Tunnels

Abstract

Snow-melt and rainfall induced landslides are major geologic hazards worldwide causing thousands of fatalities in several countries. Many failures occur along important highways, where it is particularly important to keep the roads open and in working conditions. This paper presents an analysis of an active landslide on Interstate-70 west of the Eisenhower/Johnson Memorial Tunnels where records indicate that the hillslope has moved episodically during the past 40 years with an average of over 0.6 m of displacement in two decades. A two-dimensional coupled hydro-mechanical numerical model was set up to analyze the landslide for three different infiltration rates. The framework used in the model accounts for the major physical processes in the slope: stress, deformation, and variably-saturated flow. When water infiltrates into the slope, the saturation of the soil and the water table level vary accordingly. Changes in water content of the soil suction, effective stress affect the slope stability. The model calculates total stresses, pore water pressure, suction stress, and effective stress distributions in the slope at different times. Global factor of safety as a function of time is calculated using a finite element method. The results obtained with the model are consistent with the borehole displacement data obtained by Colorado Department of Transportation (CDOT) during the years of 2007 – 2009.