INVESTIGATION OF HURRICANE IRENE’S REACTIVATION OF A ROTATIONAL LANDSLIDE ALONG ROUTE 2, IN CHARLEMONT, MA

In late August 2011, a rotational slide destroyed highway route 2 in Charlemont, MA. The slide, which had previously slipped in 1938, was reactivated by extensive rainfall (~6”) from hurricane Irene. Hurricane conditions also caused the 1938 slide. We investigate the conditions causing the reactivation of the slide in 2011 using numerical models based on subsurface soil characterization. The MA Department of Transportation characterized borehole samples in the 1970’s and again in fall 2011. Along with these logs, we collected and analyzed soil samples for current properties, such as grain size, water content, density and Atterburg Limits. We develop a three-dimensional representative model of the landslide that incorporates local topography and the topology of subsurface layers, from borehole information. A composite two-dimensional cross-section will be constructed from the complete 3D model, and imported into ComSol to simulate sliding. The ComSol model will incorporate the properties of the subsurface soils and simulate the hurricane conditions. We will vary the unconstrained soil properties and layer configurations in order to best match the observed Hurricane Irene rotational landslide along Route 2 in Charlemont.