CHANGES IN CLAY SWELLING AND SHEAR STRENGTH PROPERTIES WITH DIFFERENT SAMPLE PREPARATION TECHNIQUES

Laboratory evaluation of soil characteristics is affected by, among other things, method of preparation, disturbance of the sample, initial conditions, and remolding. The main objective of this paper is to study the influence of different compaction methods on soil swell pressure, unconfined compressive strength, and swell potential of three types of soils in Jordan. Undisturbed and disturbed soil samples were collected from the field and used for this study. Compacted soil specimens were prepared using dynamic compaction, static compaction, and kneading compaction. Swell potential tests, swelling pressure tests, and unconfined compression tests were conducted on identical soil samples compacted by different methods, and having similar initial conditions to the undisturbed samples. Other sets of experiments were also conducted to examine the influence of initial water content on swell pressure and unconfined compressive strength under different compaction techniques. Results indicated that the undisturbed samples have the highest swelling pressure and swell potential values followed by dynamic compaction, while kneading compaction gave the lowest values for the three soils. For the same soil, it has been found that the swelling pressures of the undisturbed samples were 1.5, 1.96, and 3.07 times that of the dynamic, static, and kneading compaction samples, respectively. Similar trends were obtained with regard to unconfined compressive strength and swell potential. The unconfined compressive strengths of the undisturbed samples were 1.35, 1.6, and 2.53 times higher than that of the soil specimens compacted according to the dynamic, static, and kneading procedures, respectively.