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Cohesionless Soil Definition
Cohesionless soil is a type of soil that does not stick together and is composed of loose, granular particles such as sand and gravel. It is not strong and can be easily moved by external forces such as weight or water. This type of soil is not ideal for use as a foundation for structures because it is prone to erosion and has low shear strength.
Description Of Cohesionless Soil
Cohesionless soil, also known as non-cohesive soil, is a type of soil that lacks the binding properties needed to hold larger particles together. It is characterized by its low shear strength or “stickiness,” which means that it does not have the ability to bond or “cohere” with other particles. Cohesionless soil is typically made up of sand or gravel-sized particles, and it can be found in natural or manufactured forms.
Natural cohesionless soil is often made up of clay or silt particles, which are formed through the weathering and erosion of rock and mineral deposits. Manufactured cohesionless soil, on the other hand, is created through the processing of rocks such as granite and basalt. The particles in these soils are typically smaller and more uniform in size, which makes them more suitable for use in construction projects.
One of the main advantages of cohesionless soil is its ease of excavation. Since the particles are not held together by bonding agents like water or calcium, they can be easily dug up and moved with the right equipment. This makes it an attractive option for use in a variety of construction projects, including foundation support, road bedding, and backfill for retaining walls.
However, there are also some challenges associated with cohesionless soil. One of the main drawbacks is its lack of stability, which can cause problems during construction and result in a lower-quality finished product. Cohesionless soil is prone to settling and deformation under load, which can lead to issues with structural integrity and durability. Additionally, this type of soil can be difficult to work with in wet or muddy conditions, as it becomes very dense and hard to move.
Despite these challenges, cohesionless soil is a widely used construction material due to its versatility and availability. It is an essential component of many civil engineering projects, and a thorough understanding of its properties is essential for proper design and execution of construction projects.
In conclusion, cohesionless soil is a type of soil that lacks the binding properties needed to hold larger particles together. It is commonly used in construction projects due to its ease of excavation and versatility, but it also has some challenges, including its lack of stability and tendency to compress under load. Understanding the properties of cohesionless soil is important for properly utilizing it in construction projects.
Angle Of Internal Friction For Cohesionless Soil
The angle, alpha, at which a soil anchor plate can be lifted from the ground varies depending on the type of soil. In soft cohesive soils and loose cohesionless soils, the angle may be close to 90 degrees, while in stiff cohesive soils and dense cohesionless soils, the angle may be equal to 45-Ø/2, where Ø is the soil friction angle. The ultimate uplift capacity of the soil anchor plate, Qu, is the maximum load it can withstand before being lifted from the ground. The net ultimate uplift capacity, Qnu, is the sum of the weight of the soil placed on the failure surface and the self-weight of the horizontal anchor plate, W.
Bearing Capacity Of Cohesionless Soil
Bearing capacity is the maximum pressure that a soil can safely bear without failing, or collapsing. The bearing capacity of cohesionless soil is an important factor to consider when designing foundations for structures, as it determines the size and type of foundation that is required.
The bearing capacity of cohesionless soil is primarily determined by the angle of internal friction (φ) and the effective overburden pressure at the base of the foundation. The effective overburden pressure is the total pressure acting on the soil, including the weight of the soil itself and any additional loads, such as the weight of a structure or vehicles.
The bearing capacity of cohesionless soil can be calculated using the Rankine formula, which is given by:
q_u = c_a + \gamma_a B
where q_u is the ultimate bearing capacity, c_a is the effective cohesion, γ_a is the effective unit weight of the soil, and B is the width of the foundation.
The effective cohesion of a soil is equal to the soil’s cohesion minus the overburden pressure acting on the soil. The effective unit weight of the soil takes into account the overburden pressure and is calculated as the product of the soil’s unit weight and the acceleration due to gravity.
The bearing capacity of cohesionless soil can also be affected by the size and shape of the soil particles, the degree of compaction, and the water content of the soil. It is important to consider all of these factors when determining the bearing capacity of cohesionless soil for a particular site.
Examples Of Cohesionless Soil
Cohesionless soil, also known as non-cohesive soil, is a type of soil that does not have any cohesive forces between its particles. Examples of cohesionless soils include sand, gravel, and crushed stone. These soils do not have the ability to resist shear forces, and therefore rely on their weight and the friction between the soil particles and the foundation to provide stability.