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A framework for preparation of an early warning system was developed for Maryland, using a GIS database and a collective overlay of maps that highlight highway slopes susceptible to soil slides or slope failures in advance through spatial and statistical analysis. Data for existing soil slope failures was collected from geotechnical reports and field visits. A total of 48 slope failures were recorded and analyzed. Six factors, including event precipitation, geological formation, land cover, slope history, slope angle, and elevation were considered to affect highway soil slope stability. The observed trends indicate that precipitation and poor surface or subsurface drainage conditions are principal factors causing slope failures. 96% of the failed slopes have an open drainage section. A majority of the failed slopes lie in regions with relatively high event precipitation (P > 200 mm). 90% of the existing failures are surficial erosion type failures, and only 1 out of the 42 slope failures is deep rotational type failure. More than half of the analyzed slope failures have occurred in regions having low density land cover. 46% of failures are on slopes with slope angles between 20°and 30°. Influx of more data relating to failed slopes should give rise to more trends, and thus the developed slope management system will aid the state highway engineers in prudential budget allocation and prioritizing different remediation projects based on the literature reviewed on the principles, concepts, techniques, and methodology for slope instability evaluation (Leshchinsky et al., 2015).

Karst cavities in fissured soluble rock represent serious geotechnical hazard for civil construction and urban development. The process of cavity formation, expansion, and propagation is difficult to predict because it is driven by a combination of diverse causes, such as the dissolution rate of rock; flow of groundwater; amount of fine material within rock layers; presence of loose, uncontrolled fill over the rock; and the leakage of underground utilities. Several factors can affect cavity stability, including cavity geometry and dimensions, cavity depth, overburden surface-layer lithology, and surface-loading conditions. This paper presents a case study for karst cavities stability in the Abu Dhabi Municipality (ADM) of the United Arab Emirates as part of a comprehensive study initiated by the ADM to address the geotechnical, geologic, and hydrogeological hazards encountered in the municipality. The purpose of this study is to develop a methodology for assessing karst cavities stability in the ADM, and thereby, quantify their potential hazard for civil construction and urban development in the municipality. A numerical study is performed, using a finite difference model that is based on site-specific ground conditions encountered in a localized area. Results from this numerical investigation are presented in the form of stability charts for different lithologic and surfaceloading conditions. These charts are used to develop a set of geographic information system cavity-collapse geohazard maps for the study area to factor solution cavity-collapse risk into an integrated geohazard map for the ADM. Based on available information and the case study presented herein, it is concluded that the collapse of solution cavities do not significantly contribute to the geotechnical hazard observed in the ADM.

The presence of solution cavities of different sizes poses major engineering problems in some areas of Abu Dhabi City Municipality (ADM) underlain by soluble rocks such as gypsum, calcarenite, or mudstone. This is especially critical if they are located at a relatively shallow level and are likely to cause settlement or sudden soil collapses. The Gachsaran Formation, which is composed of interlayered mudstone and gypsum, underlies all of the ADM and is known to be vulnerable to cavity formation in the area. Information associated with cavities was cataloged and reviewed based on available data from an existing geotechnical borehole database maintained by the ADM. Cavity data obtained from borehole information were analyzed to examine cavity distributions based on the following factors: lithology, geographic clusters, cavity density, cavity size, depth to cavity, and depth to bedrock. All cavities were grouped into geographic clusters and lithological clusters for point-pattern analysis. Most cavities (87 percent) occur in mudstone or gypsum, or at an interface between these two rock types, which compose part of the Gachsaran Formation. Geographically the majority of cavities occurred in the Shakhbout City area hence pattern analysis including average nearest neighbor analysis, Moran's I for measuring spatial autocorrelation, and G-statistics for measuring high/low clustering were conducted in this area using spatial statistics tools in ArcGIS. Average nearest neighbor analysis and Moran's-I show that cavities are strongly clustered in this area with a high confidence level (>99 percent). General G-statistics identified a high clustering (hot spot) of cavities with relatively high values of depth to cavity, depth to bedrock, and number of cavities per borehole. No highly clustered large cavities were detected by the General Gstatistics. Additionally, distances to the first through the nineth nearest neighbors were determined for cavities in different lithological materials and geographical clusters. Outcome of these spatial correlations and statistical analysis can be used to conduct risk assessment and the probability of occurrences of cavities in the future.

Cavity collapse and settlement due to the presence of shallow solution cavities cause significant geotechnical and other engineering problems in certain areas within the Abu Dhabi City Municipality (ADM). A cavity probability map helps to identify regions that are more susceptible to the formation of cavities by identifying and analyzing influential factors contributing to its formation. Information relating to cavities was cataloged and reviewed based on available data from the Geotechnical Information Management System (GIMS), which is a consolidated geotechnical database developed by the ADM. Geological and geotechnical subsurface conditions are obtained from previous site investigation campaigns performed in the ADM region. All geotechnical, geological, and cavity related datasets are stored in a GIS geodatabase system. Based on detailed literature review, primary factors influencing formations of cavities are identified: presence of soluble bedrock, depth to Gachsaran Formation, cavity density, cavity thickness and distance to nearest neighbor. A decision-tree model based on cavity distribution was developed for cavity hazard assessment. The primary controls on cavity development are lithostratigraphic position or bedrock geology and depth to the soluble Gachsaran Formation. Most cavities tend to form in highly concentrated zones. Implementation of the decision-tree model in ArcGIS resulted in a cavity probability map. This cavity probability map is mainly based on existing borehole data. Areas not fully mapped by boreholes must be re-evaluated for cavity risk when new borehole data is available. Low Probability, Low to Moderate Probability, Moderate to High Probability, High Probability, and Very High Probability areas were delineated in the probability map.