Soil Slope Failure Investigation Management System

Abstract

Highway slopes are exposed to environmental and climatic conditions, such as deforestation, cycles of freezing and thawing weather, and heavy storms. Over time, these climatic conditions can influence slope stability in combination with other factors such as geological formations, slope angle and groundwater conditions. These factors contribute towards causing slope failures that are hazards to highway structures and the traveling public. Consequently, it is crucial to have a soil slope failure investigation management system to track, record, evaluate, analyze and review the soil slope failure data and soil slope remediation data so that cost effective remedial plans may be developed. This paper presents the framework for developing such a system for The State of Maryland, using a database and a collective overlay of maps to indicate potentially unstable highway slopes through spatial and statistical analysis. Data for existing soil slope failures was collected from geotechnical reports and field visits. A total of 42 slope failures were recorded and analyzed. In this study, 6 factors were considered to affect highway soil slope stability: event precipitation, geological formation, land cover, slope history, ground slope and elevation. Overlaying statewide geographic information system (GIS) data for these factors reveals that precipitation and poor surface or sub-surface drainage conditions are principal factors causing slope failures. All of the failed slopes lie along roads with open drainage section. Majority of the failed slopes lie in regions with relatively high event precipitation values. Overwhelming majority (~98%) of the existing failures are surficial erosion type failures, only 2 out of the 42 slope failures are deep rotational type failures. Nearly 58% of the existing slope failures have occurred in regions having low density land cover, and about 50% of the failures have occurred in sand and 39% have occurred in gravel formations. The influx of more data relating to failed slopes should give rise to more trends, and thus this system will aid the State Highway Administration (SHA) of Maryland in prudential budget allocation and prioritizing different remediation projects.