This article describes the application of using polymer stabilization to create a new hydrophobic (nanocomposite) material with swollen clay. A series of tests were performed with different polymer contents to study the effect of using polypropylene as a partial soil stabilizer and a shrinkage-swelling modifier for expansive soils. The effect of the obtained clay-polymer nanocomposites on the shear strength of swelling soils was also investigated. The tests showed that the resulting nanocomposites acted as nanofiller materials and decreased both the plasticity index and permeability. The optimum moisture content and dry density decreased relatively with increasing polymer content. The polymer inclusions significantly reduced the free swelling and swelling pressure values. In addition, the produced nanocomposites reduced the volumetric shrinkage of the expansive soils and created isotropic and compressible materials. The unconfined compressive strength of the soil increased significantly with increasing polymer content. The proposed stabilized technique increased the bearing capacity under the model footing and modified the stress settlement relationship. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 123: 299-306, 2012