Cavities Detection and Treatment at a Residential Area under Development in the State of Kuwait

A comprehensive geotechnical investigation was carried out at a residential area under development, 20 Kilometers North of Kuwait City, by M/S Public Authority for Housing Welfare (PAHW). The investigations resulted in significant information regarding the stratigraphy and engineering and geological properties of the sub-soil. Those investigations indicated that the top layer consisted of very loose to loose silty sand with groundwater occurring at about 1.3 meters below ground surface. During excavation, a network of small interconnected cavities were found to exist at depths ranging from 0.5 to 8 meters. Those cavities were found to extend horizontally starting with depths coinciding with that of the groundwater levels at the area. This could be an indication of the existence of collapsible soils that compact and collapse upon wetting. Groundwater movement towards the sea could have caused dissolution of cemented sediments and washed out fine soils as traces of organic and salt sediments were found to exist on the cavities walls. The cavities could have also been formed due to liquefaction as several earthquakes with magnitudes ranging from 3 to 4.5 on the Richter scale struck the area in the past. It was observed that cavities did not exist in the dense layers (2–8 meters below ground surface). To reduce the risk of cavity development in the area, several soil improvement techniques were suggested. Soil placement improvement technique was chosen by PAHW and used for the whole depth of cavities occurrence.