Investigation of Reinforced Sub-Base Layer on Saturated Expansive Subgrade Soil Under Cyclic Loading

Reinforced pavement layers have been gaining popularity in the field of civil engineering due to their highly versatile and flexible nature. With the advent of geosynthetics in civil engineering, reinforced earth technique has taken a new turn in its era. The practice of reinforced earth technique became easy and simple with geosynthetics. This research required providing the materials and manufacturing of the loading machine (loading test apparatus). Materials include soil (bentonite), granular subbase, sand, and geogrid. The testing program consists of preparing of nine models that represent layers beneath flexible pavement layers subgrade and subbase layers), the model dimensions are 800×800×800 mm, subgrade layer is 400 mm thick and subbase layer 300 mm thick. The model tests include using geogrid reinforcement at the interface of the subgrade and subbase layer and in the centre of subbase layer. The tests were conducted under cyclic load, in saturation tests and tests carried out after 24 hours of saturation period. It was concluded that the load carrying capacity of the pavement system significantly increases for geogrid reinforced subbase stretch compared to unreinforced subbase layer on expansive subgrade soil. This is reflected in the values of failure load which is greater in reinforced subbase layer model than in unreinforced model. The model with geogrid reinforced saturated subbase at the interface with subgrade layer subjected to cyclic load reveals the lowest displacement and transfers the maximum load. There is a reduction in displacement of this model by about 4.5-5.0% compared with unreinforced model while the third model showed a reduction in displacement of about 3-3.5% only.