The Effect of Mastic Polyurethane B on the Mechanical Properties of Collapsible Soils

One of the most important geotechnical issues is problematic soils (dispersive soils, expansive soils, collapsing soils, liquefying soils, soluble soils …) which may affect the constructing projects on these soils and may even cancel them [1]. In this research collapsing soils are studied. A sudden collapse of the land is called collapsing. It is because the strength of the bonding among soil particles no longer exists. Studies have shown the of these soils structure need to be improved before constructing any structures on them [2]. Improvement of these soils with various substances leads to different results. The effect of Polyurethane B with different combination percentages (0.5, 1, 1.5, 2, 3 and 5 weight percentage) on improving the structure of these soils were examined. Polyurethane B is one of the most common elastomerics in engineering which has numerous uses. It has unique characteristics such as high mechanical and wear resistance, flexibility in low temperature, high cutting potential and elasticity and resistance to absorbing water, oils and solvents. The most significant feature of these polymers is that a fixed structure is obtained after reaction. In this research, direct shear test was used with stress control. Vertical pressures of 54.5, 109 and 218 Kilopascals were applied out on specimens. In order to determine the collapsing rate, ASTM D 5333-03 standard criteria were used [3]. The sample was collected from Hamidiyeh Region near Ahvaz city. Atterberg limits, simple shear test and collapsible index experiments were carried out on the specimen to determine some of the physical and geotechnical features of the soil. The results are shown in Table 1. Collapsing tests revealed that by increasing the percentage of additive substance, collapsing index decreases. The value of collapsing index for 0.5, 1, 1.5, 2, 3 and 5 combination percentages were 45%, 58%, 75%, 86% and 92%. After conducting the direct shear test on the soil which was combined with Polyurethane B, it was concluded that the most shear strength can be obtained in 1% combination percentage. In this combination, the value of adhesion and angle of internal friction were increased 27% and 3%, respectively.