Karst Limestone Geohazards in Egypt and Saudi Arabia

Abstract

Three areas in Egypt and Saudi Arabia were selected as pilot sites for studying karst foundation problems. Globally, the dissolution of carbonate rocks results in extensive karst landforms that can pose significant challenges to civil engineering projects. Most karst caves and sinkholes are structurally controlled by major faults and joints. Detection of karst limestone foundation bedrock (caves, sinkholes and open fractures) in the three studied sites has been conducted using geological and geophysical studies. The geological studies are based on review of published geologic maps for the three sites. The geophysical studies included a 2D electrical resistivity survey and ground-penetrating radar (GPR). Karst limestone foundation bedrock treatments have been performed in several projects worldwide and include engineering fill, engineering fill with geosynthetics, concrete filling and cement grout low pressure injection. Upper Egypt’s El Minia- Maghagha caves, underlying newly constructed settlement areas have been treated using high-slump concrete filling. Engineers treated foundations in northwestern Riyadh City and in eastern Al Hofuf City, Saudi Arabia, using engineering fill, high slump concrete filling and low pressure cement grout injection. This article summarizes the classification of encountered karst foundation bedrock according to Ford and Williams (1989) engineering classification, introduces the optimum methods for detecting karst features and presents engineering treatments of karst limestone landforms.