Geotechnical Engineering Test II

The correct answer is Clayey gravel. According to the IS classification, the symbol GC represents clayey gravel. This means that the soil consists of a mixture of gravel and clay particles, with the clay content being significant enough to affect the engineering properties of the soil. Clayey gravel typically has good load-bearing capacity and can be suitable for construction purposes.

The correct answer is "rock minerals" because sand particles are primarily composed of small fragments of rocks that have weathered and eroded over time. These rock minerals can include quartz, feldspar, mica, and other minerals that make up the composition of rocks.

The Highway Research Board (HRB) classification of soils is based on both particle size composition and plasticity characteristics. This means that the classification takes into account the size of the particles in the soil as well as its ability to change shape and be molded. By considering both factors, the HRB classification provides a more comprehensive understanding of the soil's properties and behavior, which is important for designing and constructing highways.

Fine grained soil is classified into silt and clay particles based on their size. Silt particles are larger than clay particles but smaller than sand particles. They have good water retention capacity and are easily transported by wind or water. Clay particles, on the other hand, are the smallest of the three types and have high plasticity and cohesion. They can retain large amounts of water and have low permeability. Therefore, the correct answer is silt and clay.

Clay has a higher plasticity index compared to the other soil types mentioned. The plasticity index is a measure of the ability of a soil to change shape and retain its shape when subjected to stress or pressure. Clay soils have small particles that can compact closely together, resulting in a high plasticity index. This means that clay soils can easily be molded and retain their shape when wet, making them more plastic compared to sand, silt, and gravel soils.

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Laboratory classification of fined grained soil is done with the help of a plasticity chart. A plasticity chart, also known as a plasticity index chart, is a graphical representation that helps determine the plasticity characteristics of a soil sample. It is used to classify soils based on their plasticity index, which is a measure of the soil's ability to undergo deformation without cracking. The chart plots the liquid limit and plastic limit values of the soil sample, allowing for easy identification of its plasticity characteristics and subsequent classification.

If the plasticity index of a soil mass is zero, it means that the soil does not exhibit any plastic behavior. This indicates that the soil does not have the ability to undergo significant deformation or change in shape when subjected to external forces. Sand is a type of soil that is composed of larger particles and has low plasticity. Therefore, if the plasticity index is zero, it suggests that the soil is predominantly sand.

The equation IP=0.73(WL-20) represents the A-line in the unified classification system table. This equation shows that the IP value is calculated by taking 0.73 multiplied by the difference between the WL value and 20. This equation helps in determining the IP value based on the WL value in the unified classification system.

ML represents inorganic soils with low compressibility. This means that these soils have a low tendency to compress under load. ML soils typically have a higher clay content, which gives them better cohesion and stability. These soils are less prone to settling or compacting, making them suitable for construction projects where stability is important.

Montmorillonite is a clay mineral that exhibits the largest swelling and shrinkage characteristics. It has a high water absorption capacity and can expand significantly when it comes into contact with water. This property makes it useful in various applications such as drilling muds, soil stabilization, and as a binding agent in ceramics. Kaolinite and illite, on the other hand, have lower swelling and shrinkage properties compared to montmorillonite. Therefore, the correct answer is montmorillonite.

The water content of soil that determines the transition from the plastic state to the liquid state is known as the liquid limit. This limit represents the moisture content at which the soil starts to behave like a liquid and loses its ability to retain its shape when molded. It is an important parameter in geotechnical engineering as it helps in understanding the soil's behavior and its suitability for various construction purposes.

The correct answer is Casagrande. Casagrande is credited with developing the Unified Soil Classification System (USCS). This system is widely used in geotechnical engineering to classify and describe different types of soils based on their properties and behavior. Casagrande's work in developing this system has greatly contributed to the understanding and analysis of soil mechanics.

When coarser particles like sand or silt are added to clay, it causes a decrease in the liquid limit, which is the moisture content at which the clay changes from a liquid to a plastic state. This is because the presence of coarser particles reduces the ability of the clay to retain water and become a liquid. Additionally, the admixture of coarser particles also leads to a decrease in the plasticity index, which is the range of moisture content over which the clay remains plastic. This is because the coarser particles disrupt the clay's ability to form a cohesive and plastic mass. Therefore, the correct answer is a decrease in both the liquid limit and plasticity index.

The uniformity coefficient is a measure of the particle size range. It is calculated by dividing the size of the sieve opening that allows 60% of the particles to pass through by the size of the sieve opening that allows 10% of the particles to pass through. A lower uniformity coefficient indicates a narrower particle size range, while a higher uniformity coefficient indicates a wider particle size range. Therefore, the uniformity coefficient is a measure of how uniform or varied the particle sizes are in a sample.

The Indian standard soil classification system, (ISCS) was first developed in 1959. This system was introduced to classify soils based on their properties and characteristics, such as texture, color, structure, and moisture content. It provides a standardized method for categorizing soils, which is essential for various engineering and construction purposes. The development of this classification system in 1959 marked an important milestone in the field of soil science in India, enabling better understanding and utilization of soils for different applications.

According to Atterberg, the plasticity index (PI) is used to classify the plasticity of soil. A soil with a PI between 7 and 17 is considered to have medium plasticity. This means that the soil has a moderate ability to undergo deformation when subjected to stress or moisture changes. Soils with medium plasticity are generally more stable than those with low plasticity, but can still be molded or shaped with some effort.

The ISCS (Indian Soil Classification System) classifies soil into 18 groups. This classification system is based on various factors such as color, texture, structure, and composition of the soil. By categorizing soil into different groups, it becomes easier to understand and analyze its properties, which is essential for various agricultural, engineering, and environmental purposes.

When the natural water content of a soil mass lies between its liquid limit and plastic limit, the soil mass is said to be in a plastic state. In this state, the soil is still moldable and can be easily deformed under stress, but it does not flow freely like in a liquid state. The plastic state is an intermediate state between the liquid state and the semi-solid state, where the soil becomes more rigid and less deformable. The solid state refers to a state where the soil is completely dry and does not exhibit any plasticity or deformability.

The uniformity coefficient of a soil refers to the range of particle sizes present in the soil. A uniformity coefficient greater than 1 indicates a wider range of particle sizes, meaning that the soil is more heterogeneous. This means that the soil contains a wider range of particle sizes, with some particles being significantly larger or smaller than the average size. Therefore, the correct answer is that the uniformity coefficient of a soil is equal to or greater than 1.

To use a textural classification chart, lines must be drawn parallel to the three sides of the triangle. This is because the chart is used to classify different textures based on their characteristics, and drawing lines parallel to the three sides allows for accurate classification and comparison of textures. Drawing lines parallel to only one side or adjacent to the sides would not provide a comprehensive representation of the textures.

Toughness index is defined as the ratio of plasticity index to flow index. This means that the toughness index is a measure of the ability of a material to deform without breaking or cracking, relative to its ability to flow. A higher toughness index indicates a material that is more resistant to cracking and has a greater ability to deform. Conversely, a lower toughness index suggests a material that is more prone to cracking and has less ability to deform.

The correct answer is "Plasticity" because according to the Unified Soil Classification System (USCS), fine-grained soils are classified based on their plasticity. Plasticity refers to the ability of a soil to undergo deformation without cracking or breaking. The plasticity of a soil is determined by conducting tests such as the Atterberg limits test, which measures the water content at which the soil transitions from a solid to a plastic state. So, the classification of fine-grained soils is primarily based on their plasticity characteristics.

At the liquid limit, all soils possess the same shear strength of small magnitude. This means that regardless of the type of soil, when it reaches its liquid limit, it will exhibit a similar level of shear strength, but this strength will be relatively low. This is because the liquid limit is the moisture content at which the soil transitions from a plastic to a liquid state, resulting in a decrease in its shear strength.

When the plastic limit of a soil is greater than the liquid limit, it means that the soil does not have enough water to reach a plastic state. In this case, the plasticity index, which measures the range of moisture content where the soil behaves plastically, is reported as zero. This indicates that the soil is non-plastic and cannot be molded or shaped.

If the material of the base of the Casagrande liquid limit device on which the cup containing soil paste drops is softer than the standard hard rubber, it means that the cup will penetrate the base more easily. This will result in a higher value for the liquid limit of the soil. Therefore, the liquid limit of soil always increases when the base material is softer than the standard hard rubber.

The symbol 'L' represents silt and clay soil types. This is because silt and clay soils are characterized by their fine texture and high water-holding capacity, which is denoted by the symbol 'L' in soil classification systems. Gravel soil, on the other hand, is represented by a different symbol, and the symbol 'L' does not represent all soil types.

In Casagrande's plasticity chart, the numbers in the chart denote the relative suitability of the soil. The chart is used to classify soils based on their plasticity index, which is a measure of the soil's ability to undergo deformation without cracking. The higher the number in the chart, the more suitable the soil is for certain engineering applications. Therefore, the numbers represent the relative suitability of the soil for different purposes.

A uniform soil has less strength and stability than a non-uniform soil because uniform soils have particles that are similar in size, resulting in a more compact and dense structure. This reduces the ability of water to flow through the soil, leading to poor drainage and increased susceptibility to erosion. In contrast, non-uniform soils have a wider range of particle sizes, allowing for better drainage and increased stability.

The correct answer is "None of the above." The first statement is incorrect because the uniformity coefficient represents the range of particle sizes in a soil sample, not the shape of the distribution curve. The second statement is also incorrect because a well-graded soil has a wide range of particle sizes, so the uniformity coefficient and coefficient of curvature would not be nearly unity. The third statement is incorrect because a well-graded soil has a variety of particle sizes, not particles of about the same size. Therefore, none of the statements are correct.