21-09-2016, 03:33 PM
1455598633-Effectofgypsumoncompactionofsoil (3).docx (Size: 131.57 KB / Downloads: 8)
Abstract:
There are several places in the world particularly middle East Asia and Africa has problem of gypsum contaminated soil known as gypsiferous soil. Gypsiferous soils cover approximately 100 million hectors in the world. Gypsum not only dissolve in presence of water it also changes geotechnical properties of soil. In the current study effect of gypsum on Atterberg limits and compaction character tics of soil was studied. Different percentage of gypsum was added with a soil from Rourkela to simulate the conditions of Gypsiferous soil. Laboratory test were conducted to determine effect of gypsum content on liquid limit, plastic limit and compaction characteristics of soil. It was noted that with increase in gypsum content liquid limit and plastic limit of soil decreased. The Maximum Dry Density (MDD) was noted to decrease continuously on increasing gypsum content. Although, some deviation were noted, in general a trend of increasing Optimum Moisture Content (OMC) was noted with increase in gypsum content.
1. Introduction
There are several places in the world particularly middle East Asia and Africa has problem of gypsum contaminated soil known as gypsiferous soil.
The origin of sulphate ions in the soil solution is in some circumstances due to the presence of sulphur-rich minerals such as pyrite in the parent material. By weathering and oxidation, the sulphur in these minerals is transformed into sulphuric acid which in calcareous soils reacts with CaCO3 to form gypsum.
On irrigated land, leaching of saline soils containing sulphate and calcium in the soil solution leads in some circumstances to the precipitation and accumulation of gypsum in the subsurface horizon. The formation of gypsum may result from replacement of NaCl by CaSO4 when the irrigation water contains a substantial amount of calcium and sulphate. But it could be also a result of a partial leaching of salts from the soil because NaCl is much more soluble than CaSO4. It has been observed in the Euphrates Basin, that gypsum is recrystallized and redistributed in the soil profile after leaching of other, more soluble, salts.
Gypsiferous soils cover approximately 100 million hectors in the world (Verheye and Boyagiev, 1997). Gypsum not only dissolve in presence of water it also changes geotechnical properties of soil. Therefore detailed investigation is required to find out the change in geotechnical properties of gypsum contaminated soil. In soils with a recent accumulation of gypsum, the salt-affected horizon overlies the gypsic horizon. In the case of old or residual gypsum, the accumulation of soluble salts occurs either in the gypsic horizon or at lower depths.
2. MATERIAL AND METHODS
Low plastic soil from Rourkela was used to for this study. Liquid limit, plastic limit and specific gravity tests were carried out using distilled water following Indian Standard Method.
2.1 Specific Gravity Test
Specific gravity of soil solids was determined using a pycnometer. Specific gravity is the ratio of the mass of unit volume of soil at a stated temperature to the mass of the same volume of gas-free distilled water at a stated temperature. Indian Standard (IS) test procedure was followed to determine the Specific Gravity of Soil Solids by Water Pycnometer. The specific gravity of a soil is used in the phase relationship of air, water, and solids in a given volume of the soil.
3. RESULTS AND ANALYSIS
3.1 Variation of Liquid Limit and Plastic Limit
Liquid Limit and Plastic Limit tests are performed on Rourkela soil by successive increment of percentage of gypsum by weight. Gypsum was added to the soil by 0.5, 1, 2, 5 and 10% by weight. The change in liquid limit and plastic limit due to increase in gypsum content is presented in Table 3.1 and Figure 3.1. It was noted that with increase in gypsum content both liquid limit and plastic limit of soil decreased.