Characterizing the Index Properties, Free Swelling, Stress–Strain Relationship, Strength and Compacted Properties of Polymer Treated Expansive CH Clay Soil Using Vipulanandan Models

In this study, the effects of a water soluble acrylamide polymer solution (PS) treatment on the index properties, compacted properties, free swelling, stress–strain relationship and compressive strength of an expansive CH soil obtained from the field in Houston, Texas was investigated. In order to characterize the clay before and after polymer treatment X-ray diffraction analyses and Thermogravimetric analyses were used respectively. In addition to characterizing the behavior of expansive CH soil (free swelling of 15%), the effect of treating the soil with a acrylamide PS was investigated and the performance was compared to 6% lime treated soil cured for 7 days at 25 °C and 100% relative humidity before testing. In treating the soil, PS content was varied up to 20% (by dry soil weight) using three different mixes (polymer content) and the soil samples were cured for 1 day at 25 °C and 100% relative humidity before testing. When the CH soil was treated with 10% PS, the liquid limit (LL) and plasticity index (PI) (index properties) of the expansive soil decreased by 33% and 57% respectively. The free swelling of the expansive soil decreased by 60% and the compacted (ASTM 698 standard method) compressive strength increased from 126 to 496 kPa. Polymer treatment also increased the compacted maximum dry density and reduced the optimum moisture content of the treated CH soil. The behavior of the LL, PI and swelling of the expansive soil treated with different percentages of the PSs have been quantified using the Vipulanandan property correlation model. Compressive stress–strain relationships of the expansive soil treated separately with lime and PS have been modelled using the nonlinear Vipulanandan p–q stress–strain model. The stress–strain model parameters were sensitive to the polymer content and the type of treatment.