Abstract
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 (36o) 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
Highlights
It is a fact that soils are extremely complicated engineering materials whose constitutive response depends on many factors, including soil type, density, water content, structure, particles size, drainage conditions, duration of loading, stress history, confining pressure, and stress path [1,14].The gypseous soil forms approximately (27-36) percentage of Iraqi soils and this type of soil is the source of many problems in the engineering structures which are built on it.Soil improvement techniques fall under several categories, the improvement can takes place by densification, reinforcement, removal and replacement and physico-chemical alterations
The dynamic compaction method was used to save cost and time relative to the other methods [4]. By this method the soil densification can be achieved to significant depths by applying high energy impacts at the surface of the soils to ensure that the required characteristics are obtained
This study as stated before, was conducted on gypseous soil found in Bajii city (160 km South of Mosul city)
Summary
It is a fact that soils are extremely complicated engineering materials whose constitutive response depends on many factors, including soil type, density, water content, structure, particles size, drainage conditions, duration of loading, stress history, confining pressure, and stress path [1,14].The gypseous soil forms approximately (27-36) percentage of Iraqi soils and this type of soil is the source of many problems in the engineering structures which are built on it.Soil improvement techniques fall under several categories, the improvement can takes place by densification, reinforcement, removal and replacement and physico-chemical alterations. The dynamic compaction method was used to save cost and time relative to the other methods [4] By this method the soil densification can be achieved to significant depths by applying high energy impacts at the surface of the soils to ensure that the required characteristics are obtained. These impacts generate improvement from vertical and lateral displacement in the soil surrounding the impact point as well as from powerful shock waves occure in short duration which promote the re-arrangement of the soil particles into the denser configuration [9]
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