27-08-2014, 12:34 PM
Soil which is composed of very fine particles, usually silicates of aluminum and/or iron and magnesium. Clay soil impedes the flow of water, meaning it absorbs water slowly and then retains it for a long time. Wet clay soil is heavy and sticky, and tends to swell from the added moisture. When dry, clay soil shrinks and settles. The top layer can bake into a hard, concrete-like crust which cracks. Some plants have difficulty growing in clay soil because their seedlings or roots are unable to penetrate through hard, dry soil, or can be waterlogged in wet soil. Adding organic material to clay soil is an effective method of improving growing conditions. ISO 14688 grades clay particles as being smaller than 2 μ mm Individual clay particles are always smaller than 0.004 mm. Clays often form colloidal suspensions when immersed in water, but the clay particles flocculate (clump) and settle quickly in saline water. Clays are easily molded into a form that they retain when dry, and they become hard and lose their plasticity when subjected to heat.
STANDARD PROCTOR TEST
MATERIALS AND EQUIPMENT:
Cylindrical metal mould of capacity 1000cc, with an internal diameter of 1000.1mm and an internal effective height of 127.30.1mm, mould fitted a detachable base and a removal extension approximately 60mm high, metal rammer, 50mm dia circular face, weighing 2.6kg and having drop of 310mm, steel straight edge, balances, oven, water content containers, mixing equipment, such as mixing pan, spoon, trowel etc, measuring cylinder of glass, 100ml capacity
THEORY:
Compaction is the process of increasing the bulk density of a soil or aggregate by driving out air. For any soil, for a given amount of compactive effort, the density obtained depends on the moisture content. At very high moisture contents, the maximum dry density is achieved when the soil is compacted to nearly saturation, where (almost) all the air is driven out. At low moisture contents, the soil particles interfere with each other; addition of some moisture will allow greater bulk densities, with a peak density where this effect begins to be counteracted by the saturation of the soil
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PROCEDURE:
• Take a representative sample weighing approximately 1.5 kg of thoroughly mixed air dried material passing 4.75mm sieve.Add enough water to bring its water content to about 7% less than estimated optimum moisture content
• Clean the mould and fix it to the base. Take the empty mass of the mould and the base, nearest to1g.
• Attach the collar to the mould .the inside of the mould may be greased thoroughly.
• Mix the matured soil thoroughly. Take out about 2.5kg of the soil and compact it in the mould in three equal layers, each layer being given 25 blows from the rammer weighing 2.6kg dropping from a height of 310mm, if 1000ml mould is used. If, however, the 2250ml mould is used about 5kg of soil should be taken, and should be compacted in three equal layers each layer being given 25 blows from the rammer weighing 2.6kg dropping from height of 310mm. The blows should be uniformly distributed over the surface of each layer.
• Remove the collar and cut the excess soil with the help of straight edge. Clean the mo0uld from outside, and weigh it to the nearest gram. Eject out the soil from the mould, cut it in the middle and keep a representative soil specimen for water content determination.
• Repeat the experiment five or six time, using a fresh part of the soil specimen and after adding higher water content than preceding specimen.
A geogrid is geosynthetic material used to reinforce soils and similar materials. Geogrids are commonly used to reinforce retaining walls as well as subbases or subsoils below roads or structures. Soils pull apart under tension. Compared to soil, geogrids are strong in tension. This fact allows them to transfer forces to a larger area of soil than would otherwise be the case.
Geogrids are commonly made polymer materials, such as polyester, polyethylene or polyproylene. They may be wovern or knitted from yarns, heat-welded from strips of material, or produced by punching a regular pattern of holes in sheets of material, then stretched into a grid.