Field investigation for comprehensive assessments of four selected stabilization methods for soft subgrade soils

The long term performance of the pavements constructed on subgrade soils of poor properties such as low strength and high swell characteristics is highly affected by the poor soil properties. The pavement distress due to swell movements of the subgrade soil leads to pavement ponding problems, riding discomforts and future traffic delays due to repair jobs and partial closure of the roads. The failure to improve soil properties will result in high annual costs for repairs and maintenance. This research applies four stabilization methods to enhance strength and swell properties of pavement base course. A great deal of laboratory tests had already been performed and some more were performed by the author to obtain properties of the natural soil from south Arlington and treated soils. The laboratory tests include unconfined compressive strength test, resilient modulus test, linear shrinkage, atterberg limits and dynamic cone penetration test. In order to assess the performance the these four stabilization methods dynamic cone penetration tests were performed in the field and then the results from field testing along with laboratory results were studied to come up with a useful and cost effective stabilization method. The road sections studied in this research are parts of a low volume of traffic road and that AASHTO manual (1993) was used to obtain modulus of subgrade reaction. In order to examine the usefulness of utilizing DCP equipment in the field, DCP was used in the laboratory condition on two treated soils. These were lime and cement treated soils. The DCP results obtained in the laboratory condition agreed closely with the unconfined compressive strength test results performed in the laboratory. This proved the effectiveness of application of DCP as a means for obtaining the strength properties of the treated soil of pavement subgrad.