Improving The Engineering Properties of The Gypseous Soil Using Dynamic Compaction Method

The aim of this study is to improve the engineering properties of gypseous soils, located in Bajii city (160 km South of Mosul city) using the Field Dynamic Compaction (FDC) techniques.  This technique consist of dropping a reinforced concrete block (1x1x1 m) weighing (2.4 Tons) from different heights on a gypseous soil of thickness varaing from (0.5-2.4 m) and underlain by sub-base material. The effect of FDC on the gypseous soil was investigated using SPT in the field and using the conventional laboratory apparatus in the laboratory tests. The results showed that the unit weight increased (14-32%) for one drop of the weight. The effective angle of internal friction (ϕˉ ) increased from (32 o ) to about (36 o ) while the compression index (Cc) decreased from (0.24) to about (0.07-0.1). The results of this study indicated that about (60-80 %) of the improvement was achieved from the first blow in loose to meduime soils. However about (25 %) of the improvement was reached in dense soils. The FDC is a promising technique for improving the engineering properties of gypseous soil and overcome most of the gypseous soil problems. Key words: Dynamic compaction ,  Gypseous soil, Soil Improving and SPT-Test