Transported soil Plasticity index (Ip).

Plasticity index (Ip). The range of consistency within Soil structure • Capillary tension or Capillary potential : due to the
1. Glacial soils—formed by transportation and which a soil exhibits plastic properties is called plastic • Soil structure is defined as the geometric arrangement tensile stress caused in water. It is the pressure deficiency
deposition of glacier range and is indicated by plasticity index. The plasticity of soil particles with respect to one another. (or pressure reduction or negative pressure) in pore
2. Alluvial soils—transported by running water and index is defined as the numerical difference between the • factors affect the structure : shape, size, and water by which water retained in a soil mass. Range: hc
deposited along streams liquid limit and the plastic limit of a soil: Ip = WL-WP mineralogical composition of soil particles, and the γw to zero
3. Lacustrine soils—formed by deposition in quiet Consistency index (IC). The consistency index or the nature and composition of soil water. • Soil suction (or suction pressure) : the pressure
lakes relative consistency is defined as the ratio of the liquid • In general, soils can be placed into two groups: deficiency in the held water of soil
4. Marine soils—formed by deposition in the seas 5. limit minus the natural water content to the plasticity cohesionless and cohesive. • Soil suction affected by particle size, water content,
Aeolian soils—transported and deposited by wind index of a soil: Ic = WL-W/Ip plasticity index, history of drying and wetting, soil
6. Colluvial soils—formed by movement of soil from Liquidity index (I1). The liquidity index or water-plasticity structure, temperature, denseness of soil, angle of
its original place by gravity, such as during landslides ratio is the ratio, expressed as a percentage, of the contact, salt present in soil and water,.
natural water content of a soil minus its plastic limit, to
its plasticity index:
IL=W-Wp/Ip

• Total stress (σ)= stress/ pressure on any plane of the Stress conditions in dry soil Isobars: factors that affect the permeability of soil:
soil mass. Due to Self weight & overburden • Total stress (σ)= height of soil (h) x unit weight of soil (γ) Isobars are lines or surfaces that connect points of equal 1. Particle size and distribution
• Total stress (σ)=intergranular pressure or effective • pore water pressure(u) = piezometric head (hw ) x unit pressure or stress in a material. In the context of soil 2. Void ratio and porosity
pressure (σ′) + neutral or pore water pressure(u) weight of water (γw ) mechanics, isobars are used to represent the distribution 3. Soil structure and fabric
• Total stress (σ)= height of soil (h) x unit weight of • Effective pressure (σ′) = Total stress (σ) - pore water of pressure or stress within a soil mass. Isobars can be 4. Degree of saturation
soil (γ) pressure(u) used to visualize the pressure distribution around a 5. Soil density and compaction
• Total unit weight of soil (γ) = Soil + water foundation, tunnel, or other underground structure. 6. Presence of impurities or contaminants
• Effective unit weight of soil (γ′)= saturated unit Stress conditions in submerged soil Pressure Bulbs: 7. Temperature and moisture content
weight of soil (γsat) - unit weight of water (γw ) • Total stress (σ)= height of soil (h) x unit weight of soil (γ) A pressure bulb is a graphical representation of the
• pore water pressure(u) = piezometric head (hw ) x • pore water pressure(u) = piezometric head (hw ) x unit pressure distribution around a loaded area, such as a
unit weight of water (γw ) weight of water (γw ) foundation or a footing. The pressure bulb is typically
• Effective pressure (σ′) = Total stress (σ) - pore water depicted as a series of concentric circles or ellipses, with
pressure(u) the pressure decreasing as you move away from the
center of the loaded area. The shape and size of the
pressure bulb depend on the type of soil, the load
applied, and the depth of the loaded area.
The particle size distribution (PSD) curve for a soil is Compaction of soil factors: critical hydraulic gradient and quicksand condition: The consistency of soil refers to its physical state or
typically determined through a combination of 1. Moisture Content: The moisture content of the soil has Critical Hydraulic Gradient: behavior when it is subjected to various forces, such as
laboratory tests and calculations. Here's a step-by- a significant impact on its compactibility. Soils with The critical hydraulic gradient is the maximum hydraulic compression, tension, or shear. The consistency of soil is
step guide on how to find out the PSD curve for a soil: optimal moisture content (around 10-20%) are more gradient that a soil can withstand without failing or an important property that affects its behavior and
Laboratory Tests: easily compacted than soils that are too dry or too wet. becoming unstable. It is the gradient at which the performance in various engineering applications, such as
1. Sieve Analysis: A soil sample is passed through a 2. Soil Type: Different soil types have varying degrees of seepage force equals the frictional force between the soil foundation design, pavement construction, and
series of sieves with different mesh sizes to separate compactibility. Soils with high sand content, for example, particles, causing the soil to lose its strength and become earthwork.
the particles into different size fractions. The weight are more easily compacted than soils with high clay liquefied. The critical hydraulic gradient is typically Types of Consistency:
of each fraction is recorded. content. denoted by the symbol (i_c) and is expressed as a ratio of 1. Liquid Consistency: Soil is in a liquid state and has no
2. Hydrometer Analysis: A soil sample is mixed with 3. Compaction Method: The method of compaction used the hydraulic head to the length of the soil. shear strength.
water to create a suspension, and then a hydrometer can also impact the degree of compaction. For example, Quicksand Condition: 2. Plastic Consistency: Soil is in a plastic state and can be
is used to measure the density of the suspension at rolling compaction can be more effective than tamping Quicksand is a condition that occurs when a soil becomes molded or shaped.
different times. This allows for the calculation of the compaction for certain soil types. saturated with water and loses its strength, causing it to 3. Semi-Solid Consistency: Soil is in a semi-solid state and
particle size distribution of the finer particles (silt and 5. Soil Structure: The structure of the soil, including the behave like a liquid. This occurs when the hydraulic has some shear strength.
clay). arrangement of particles and the presence of aggregates, gradient exceeds the critical hydraulic gradient, causing 4. Solid Consistency: Soil is in a solid state and has high
Calculations: can affect its compactibility. the seepage force to overcome the frictional force shear strength
1. Sieve Analysis Data: The weight of each size 7. Temperature: Temperature can impact the between the soil particles. As a result, the soil particles Factors Affecting Consistency:
fraction from the sieve analysis is plotted against the compactibility of soil, with higher temperatures generally become suspended in the water, creating a soupy or 1. Water Content: The amount of water in the soil affects
corresponding sieve size to create a cumulative making it easier to compact. liquid-like consistency. Quicksand can be hazardous, as it its consistency.
weight curve. 8. Pressure: The pressure applied during compaction can can cause structures to sink or collapse, and can also be 2. Soil Type: Different types of soil have different
2. Hydrometer Analysis Data: The density readings affect the degree of compaction. Higher pressures can difficult to escape from. consistencies.
from the hydrometer analysis are used to calculate result in greater density and lower air voids. 3. Compaction: Compaction can affect the consistency of
the particle size distribution of the finer particles 9. Soil Organic Matter: The presence of organic matter in soil.
using Stokes' Law. the soil can affect its compactibility, with soils high in 4. Temperature: Temperature can affect the consistency
3. Combining Sieve and Hydrometer Data: The data organic matter generally being more difficult to compact. of soil.
from the sieve and hydrometer analyses are Methods of Measuring Consistency:
combined to create a complete PSD curve. The consistency of soil can be measured using various
methods, including
1. Atterberg Limits: The Atterberg limits are a set of tests
used to determine the consistency of soil.
2. Proctor Test: The Proctor test is a method used to
measure the consistency of soil.
3. Triaxial Test: The triaxial test is a method used to
measure the shear strength of soil.

A hydrometer is a laboratory instrument used to measure A flownet is a graphical representation of the flow of The Indian Standard (IS) soil classification system is a
the density of a soil suspension, which is a mixture of soil water through a porous medium, such as soil or rock. It is widely used system in India for classifying soils based on
and water. The hydrometer is used to determine the a two-dimensional representation of the flow field, their engineering properties. The system was developed
particle size distribution of a soil, which is an important showing the direction and magnitude of the flow at by the Bureau of Indian Standards (BIS) and is based on
property in geotechnical engineering. different points in the medium. the Unified Soil Classification System (USCS) developed
Hydrometer Analysis: Uses of a Flownet: by the American Society for Testing and Materials
The hydrometer analysis is a method used to determine 1. Visualize the flow field: A flownet provides a graphical (ASTM).
the particle size distribution of a soil. The analysis representation of the flow field, making it easier to Overview of the IS Soil Classification System:
involves mixing a soil sample with water to create a understand the direction and magnitude of the flow. The IS soil classification system is a hierarchical system
suspension, and then measuring the density of the 2. Determine the hydraulic head: The hydraulic head at that categorizes soils into different groups based on their
suspension at different times using a hydrometer. The different points in the medium can be determined from particle size distribution, plasticity, and other engineering
density of the suspension is related to the amount of soil the flownet. properties. The system consists of the following main
particles that have settled out of the suspension, which is 3. Calculate the flow rate: The flow rate through the categories:
in turn related to the particle size distribution of the soil. medium can be calculated from the flownet. 1. Coarse-grained soils: Soils with a high percentage of
Corrections Applied to Hydrometer Analysis: 4. Design drainage systems: A flownet can be used to coarse-grained particles, such as sand and gravel.
There are several corrections that need to be applied to design drainage systems, such as those used in 2. Fine-grained soils: Soils with a high percentage of fine-
the hydrometer analysis to obtain accurate results. These agricultural fields or construction sites. grained particles, such as silt and clay.
corrections include: 5. Analyze groundwater flow: A flownet can be used to 3. Organic soils: Soils with a high percentage of organic
1. Temperature correction: The density of the suspension analyze the flow of groundwater through aquifers and matter.
is affected by the temperature of the suspension. A other geological formations. Subcategories:
temperature correction is applied to account for this Advantages of a Flownet: 1. Coarse-grained soils:
effect. 1. Simple and intuitive: A flownet is a simple and intuitive 2. Fine-grained soils:
2. Meniscus correction: The meniscus is the curved way to visualize the flow field. 3. Organic soils:
surface of the suspension that forms at the top of the 2. Easy to construct: A flownet can be constructed using a Classification Criteria:
hydrometer cylinder. A meniscus correction is applied to few simple steps. 1. Particle size distribution: The percentage of different
account for the effect of the meniscus on the density 3. Useful for complex problems: A flownet can be used to particle sizes, such as sand, silt, and clay.
reading. analyze complex flow problems, such as those involving 2. Plasticity: The ability of the soil to change shape
3. Dispersion correction: The dispersion correction is anisotropic or heterogeneous media. without breaking.
applied to account for the effect of soil particles that are Limitations of a Flownet: 3. Liquid limit: The moisture content at which the soil
not fully dispersed in the suspension. 1. Two-dimensional representation: A flownet is a two- changes from a liquid to a plastic state.
4. Viscosity correction: The viscosity correction is applied dimensional representation of the flow field, which may 4. Plastic limit: The moisture content at which the soil
to account for the effect of the viscosity of the not accurately represent the actual three-dimensional changes from a plastic to a semi-solid state
suspension on the density reading. flow. Symbols and Notations:
2. Assumes steady-state flow: A flownet assumes steady- 1. G: Gravelly soils. 2. S: Sandy soils. 3. C: Clayey soils.
state flow, which may not be the case in all situations. 4. M: Silty soils. 5. O: Organic soils.
3. Limited to porous media: A flownet is limited to Advantages:
analyzing the flow of water through porous media, and 1. Simplified classification:
may not be applicable to other types of flow problems. 2. Wide applicability:
3. Engineering relevance:
Limitations:
1. Limited detail: The system may not provide sufficient
detail for certain geotechnical engineering applications.
2. Subjective interpretation: The system requires
subjective interpretation of soil properties, which can
lead to inconsistencies.