Evaluation of Collapse Potential of Risalpur Soil

Abstract

Collapsible soils have known to cause major damage to structures and facilities all over the world. These soils which have excellent strength and stiffness properties in dry conditions undergo a sudden reduction in volume when exposed to water. Buildings in Risalpur cantonment show severe signs of distresses in form of extensive cracking, settlement and at times tilting. Geological evidence show that soil deposits in Risalpur are mostly alluvial and loess deposits which together with hot and humid climate favors formation of collapsible soils. A study has been conducted to investigate the possibility of collapsing soils as a probable cause of cracking and settlement of buildings. Soil was characterized up to a depth of 20 feet, i.e., zone of influence of shallow foundations. Existing criterion for identification of collapsible soils indicated the presence of collapsible soils up to the depth of investigation. Detailed investigations were carried out to using single oedometer tests, standard penetration tests, unconfined compression tests and plate load tests. All these tests indicated severe collapse potential especially at 4 feet depth. For example, single oedometer test at 4 feet depth indicated a collapse potential of seventeen percent when the specimen was flooded under a load of 200kPa. A preliminary study was also conducted to ascertain the feasibility of use of stone columns to mitigate collapse of Risalpur soil. The stone column improved the load carrying capacity and reduced the settlement under flooded conditions; however, more detailed study is required to determine the optimum area ratio for most economical and efficient stone columns