Assessment of the collapse mechanisms of tufa deposits

This research assesses the collapse mechanisms of tufa deposits. The city of Antalya, located on the Mediterranean coast of Turkey, has been settled on tufa deposits. By the end of 1980s, the area behind the tufa cliffs became the site of high-rise residential buildings. Some of these buildings have suffered from foundation instabilities, which have given rise to cracking and fissuring of the walls, and overall tilting. The collapsible behaviour upon loading and/or wetting of some tufa deposits has caused foundation settlement. bonding of grains and grain properties of the collapsible tufa were investigated using optical and scanning electron microscopes. Our studies indicate that the collapse behaviour of tufa is affected mainly by depositional environment and microfabric. Laboratory tests have been performed in order to determine the index properties and the collapse potential of tufa samples. Young tufa deposits near the surface are weakly bonded with thin films of carbonate cement, giving rise to high void ratios. Analysis of geotechnical parameters has shown that the collapse potential of tufa is closely related to the natural void ratio and the amount of cement binding the grains.