A Study on the Effects of Waste Rubber Tire Dimensions on Fine-Grained Soil Behavior

Mashhad city is located on alluvial deposits where the expanded area of this city, especially the central and eastern areas surrounding Imam Reza holy shrine, are built on weak and fine-grained deposits. Therefore, the soil improvement would be inevitable due to construction of highrise buildings such as hotels and commercial complexes in these areas, as well as restructuring old buildings. Today, the use of waste rubber tire to stabilize the soil is not only efficient to secure human health and clean the environment but also as an inexpensive additive to improve the behavior of problematic soils. In this research, waste rubber tires in three different dimensions (<1 mm, 1-2 mm and 2-4 mm) and six weight ratios (0%, 0.5%, 1%, 2.5%, 5%, 7.5%, and 10%) were investigated in a laboratory scale to examine the behavior of fine-grained soils reinforced with granular rubber tires as a suitable replacement for reinforced concrete piles in old buildings. The results showed that adding these rubber tires could reduce the density, optimum moisture content, and settlement, and increase the shear strength parameters and bearing capacity of the soil. The best weight ratio to increase the strength and reduce the settlement of this soil contained five percentage of rubber tire smaller than 1 mm in size leading to a 46% increase in bearing capacity and a 70% decrease in the settlement of the soil around the Razavi holy shrine.