Treatments of Highly Erodible Lands Considered as Geotechnical Hazards in Highway Construction: In Case of Adama ?��? Awash Expressway Road Project

Abstract

Highly erodible lands which contain dispersive soils are one of the main geotechnical hazards for highway construction. Dispersive soil is one of the problematic soils which erodes or dislodges easily in the presence of flowing water due to the presence of a high percentage of exchangeable sodium ions in the soil particles. This study aspires to investigate erosion related hazards and treatments of highly erodible lands considered as geotechnical hazards in highway construction by taking Adama ?�? Km 60 expressway project in case study. To achieve the objective of the study both field investigation and laboratory experiment approaches were utilized. Field investigation revealed that the project under study is suffering from serious erosion related problems. For this study totally 75 crumb tests were conducted together with engineering property tests for eight dispersive soil samples along with pumice and gypsum soil blend samples. All eight soil samples showed dispersive property with dispersive grade-4. One soil sample collected from cut section of the expressway proven to be dispersive and highly sodic soil by double hydrometer and chemical test with a value of 80% and 24.41 ESP respectively. The suitability of gypsum and pumice as a treatment options was checked by using crumb test. According to crumb test results specimen treated by gypsum and pumice with different proportions showed dispersive nature and it is proven that gypsum and pumice are out of the treatment options. According to crumb test and engineering property test results there is no relation between soil dispersiveness and engineering properties like atterberg limits and CBR value. From field investigation, scoria material blended with 30% of dispersive soil found to be suitable for soft shoulder and median earth ditch erosion prot