Based on the research that will be carried out, graph of shear strength versus percentage of water content will be plotted. From this graph, the suitable percentage of water content to perform a high shear strength soil can be determined. This information helps engineers in estimating the load that can be transferred to the clay soil. However, the achieving results are limited for clay soil in RECESS KUiTTHO because the properties, behaviour and structures of clays are different base on area.
Study Area
This research is focusing on clay soil. It includes of soil investigation for the purpose of ground improvement. Clay soil will be investigated from the aspect of shear strength. There are many factor influences the level of shear strength. One of them is the percentage of moisture content. That is why the moisture content in clay soil will be investigated to find out their capability in changing the shear strength of clay soil.
Literature Review
The term soil conveys varying shades of meaning when it is used in different contexts. To a geologist it describes those layers of loose unconsolidated material extending from the surface to solid rock, which have been formed by the weathering and disintegration of the rocks themselves. An engineer, on the other hand, thinks of soil in terms of the work he may have to do on it, in it or with it. In an engineering context soil means material that can be worked without drilling or blasting. Pedologists, agriculturalists, horticulturalists and others will also prefer their own definitions [2].
For engineering purposes soil is best considered as a naturally (mostly) occurring particulate material of variable composition having properties of compressibility, permeability and strength. All soils originate, directly or indirectly, from solid rocks and these are classified [2]. According to McCarthy, in nature, soils are made up of particles of varying size and shape. To distinguish between soil where size cannot be visually discerned (the particles are too small), an additional property, plasticity is used as criterion. Study has proved that a soil's important behavioural properties are not always controlled by particle size and plasticity. Soil structure and mineralogical composition and their effect with water, may also have significant influence on the properties and behaviour deemed important for design and construction [8].
Clay Soil
The most significant properties of clay are its cohesion and plasticity. If when pressed together in the hands at a suitable moisture content the particles stick together in a relatively firm mass, the soil shows cohesion. If it can be deformed without rupture (i.e. without losing its cohesion), it shows plasticity. Clay dries more slowly than silt and slicks to the fingers; it cannot be brushed off dry. It has a smooth feel, and shows a greasy appearance when cut with a blade. Softer consistencies behave rather like butter, and harder consistencies like cheese. Dry lumps can be broken, sometimes with difficulty, between the fingers, but cannot be powdered. A lump placed in water remains intact.
Clay does not exhibit dilatancy. Lumps shrink appreciably on drying, and show cracks which are the more pronounced the higher the plasticity of the clay. At a moisture content within the plastic range, clay can easily be rolled into threads 3mm diameter which for a time can support their own weight. Threads of high-plasticity clay are quite tough; those of low-plasticity clay arc softer and more crumbly [12].
Properties of Clays
Because of the small particle diameter and plate-like shape of clays, the surface area to mass ratio is much greater than in other soils. This ratio is known as the specific surface. For example, montmorillonite has a specific surface of about 800 m2/g, which means 3.5 g of this clay has a surface area equal to that of a football field.
The large specific surface of clays provides more contact area between particles, and thus more opportunity for various interparticle forces to develop. It also provides more places for water molecules to attach, thus giving clays a much greater affinity for absorbing water. Some clay can easily absorb several times their dry weight in water. The interactions between this water and the clay minerals are quite complex, but the net effect is that the engineering properties vary as the moisture content varies. For example, the shear strength of a given clay at a moisture content of 50% will be less than at a moisture content of 10%.
Formation of Clay Soils
On a slightly larger but still microscopic scale, clay minerals are assembled in various ways to form clay soils. These microscopic configurations are called the soil fabric, and depend largely on the history of formation and deposition. For example, a residual clay, which has weathered in-place and is still at its original location, will have a fabric much different from a marine clay, which has been transported and deposited by sedimentation. These differences are part of the reason such soils behave differently [10].
