Contribution to the behavior study and collapse risk of underground cavities in highly saline geological formations

Abstract

The problem of saline soils reserved from occupation at Oran, North Algeria remained relatively unexplored or little known until recent years. Consequently, some studies were conducted, especially to characterize the real impact of an airport on these soils. The characterization of the real problems of saline soils, as well as the study of the behavior of their collapse under the coupled effect of thermal, mechanical and hydraulic, remains poorly known specially under an airport, where the instabilities and the risks of sudden collapses is an unknown problem for the authorities and citizens and the impact on the environment is not mastered. Under the action of water charged with carbon dioxide which dissolves the limestone, chalk or gypsum, many natural cavities are created. There are also pockets of dissolution filled with silt in the chalk, due to the irregularity of the contact chalk/silt. The flow of water can also enlarge the fractures at depth causing the silt that fills them and thus creating a surface subsidence due to infiltration. This phenomenon is found mainly in the dry valleys. To account for the effect of the hydro-thermomechanical coupling in predicting the collapse of saline soils, solutions were proposed for improvement of saline soil with a geosynthetic reinforcement, drainage, etc. These solutions are necessary for the proper design of airfield runways to avoid a disaster.