Soil consistency refers to the soil’s ability to hold together and maintain its shape when manipulated or stressed. It can vary depending on factors like moisture content and the type of soil. Soil consistency is typically described using terms like “loose,” “firm,” “plastic,” “sticky,” “compact,” and “cohesive,” among others.
What is consistency of soil?
Consistency of soil is refers to degree of firmness of a soil termed like as firm, stiff, hard, soft which is relative ease with soil can be having properties as deformation or rupture that is use for the predicting the behaviour of soil infills, pavement and its strength.
Consistency of soil must be evaluated by fine grained soil, as especially clay which is depend into water content, when fine grained soil is mixed with addition of moisture, the water reduces the cohesion, resulting the soil still to make easier to mould and the form a plastic paste which is moulded into any form by pressure and further mixing of water reduces the cohesion untill the material no longer retains its shape under its own weight.
Consistency of limit or Atterberg limit test
Consistency of limit is the a type of test in fine grained soil especially clay and silt soil transition in various form due to enough water may be added until the soil gains are dispersed in a suspension, then water is evaporated from such a soil suspension, the soil passes through the various stages to change from solid to semi solid to plastic to liquid states, the water contents at which the consistency changes from one state to the other are called consistency limits or atterberg limits.
Consistency of limit is the associated with the field using simple test or may be measured more accurately in the laboratory for soil samples in form of wet, moist and dry for the predicting the behaviour of maintaining the right soil for use of intended to support structures, pavements,or other loads that is resistance capability under applied forces and variable moisture conditions.
Important of Atterberg limit test
Atterberg limit test are the associated with fine grained soil, especially in clay in consist soil samle in form of wet, moist and dry soil in which the limits of water content used to define the soil behaviour through the various stages to change from solid to semi-solid and plastic to liquid limit accordingly increase in water content that exhibit strength of soil, classifying a soil type or predicting soil performance to used in a construction material.
Atterberg limit test is also measured the moisture content, shear strength , particles size distribution and the potential for essential to support construction structures, pavement or othe loads must be evaluated by geotechnical engineers to predict their behaviour under applied forces and variable moisture conditions.
This test values and derived indexes have direct applications in the foundation design of structures and in predicting the behaviour of soil infils, embankments and pavements, the values asses shear strength, estimate permeability,forcast settlement and identify potentially expansive soils.
What are stages and limit of soil consistency/ Atterberg soil limit test
Atterberg analysed the consistency of soil is four stages, these are following-:
2. Semi solid
Consistency of the soil is various with water content and the water content at which soil passes from one stage of consistency to another such as solid to semi-solid and plastic to liquid is called the consistency limit or atterberg limits which are following as-:
1. Liquid limit
2. Plastic limit
3. Shrinkage limit
What is liquid limit of soil
Regarding this,” what is liquid limit of soil?”, liquid limit is denoted by WL, it is defined as the minimum water content at which soil is in liquid state of consistency or it may also be defined as a minimum water content at which the soil behaves as tendancy to flow which characteristics of liquid limit of soil used for the identification of soil and classification of soil and also use for classify fine grained soils and predicting the engineering properties in construction .
At liquid limit, soil passes from plastic stages of consistency to liquid stage of consistency or vice versa that behaviour of soil is called liquid limit.
Important point of Liquid limit of soil
1. If the liquid limit of the soil is higher, then it’s properties behaviour of Plasticity is higher.
2. Also the volume changes observed in it is higher .
3. It means higher is its compressibility behaviour.
4. Liquid limit is defined only for fine grained soil
Types of soil having liquid limit in percentage
1. Gravel-: Non plastic
2. Sand -: Non plastic
3. Silt -: 30 to 40
4. Clay (Alluvial soil)-: 40 to 150
5. Clay ( Black soil) -: 400 to 500
6. Clay (Bentonite soil)-: 400 to 800
What is liquid limit?
Liquid limit-: Liquid limit is the widely used all over the world and play a important roll for soil identification and classification of soil, in this consistency of soil behaviour having liquid limit expressed as percentage is changes accordance to types of clay soil and silt, from this point of view of determination of liquid limit is the contain minimum water content at which part of the soil cut by a groove of standard dimensions will flow together for a distance of 12 mm under an impact of 25 times of the device.
Liquid limit has determined by Casegrande tool having dimensions bottom width 2 mm, top width 11 mm and height 8 mm is generally used for less plastic soil like silt and Astm tool having dimensions bottom width 2 mm, top width 13.5 mm and height 10 mm is generally used for high plastic soil like clay.
Liquid limit formula
Liquid limit consist the approximate water content at that limit, behaviour of soil begins as a liquid which is used to define the mechanical properties of soil with the help of liquid limit formula that is difference between the weight of dry soil sample to the weight of a wet soil samples and multiply by 100.
How to find liquid limit
Regarding this, “how to find liquid limit?”, determining the liquid limit described by the two methods cone penetrometer method and Casegrande apparatus method using apparatus liquid limit device, soil mixture equipment, oven, containers for determination of water content and sieve no40 (0.425 mm) that is procedure for atterberg limits to characterize fine grained soil especially in clay which consists a fine grained soil placed in brass cup and cut with a standard groove and then dropped from a height of 10 mm resulting will undergo a groove closer of 13 mm when it’s dropped 25 times.
In this consistency, “how to find liquid limit?”, by above process we shall be finding the water content for each dropped times, to plot the semi logarithmic chart in which water content as linear against the corresponding numbers of blows as log scale.
In semi logarithmic chart draw the best straight line fitting the plotted points that is called flow curve and draw the 25 blows ordinate where intersect the flow curve draw the horizontal line to the water content axis, this value of water content is equal to Liquid limit of the soil .
Plastic limit soil
Plastic limit soil -: It is denoted by Wp ,it is defined as the minimum water content in which soil in plastic stage of consistency that is passes from semi solid stage of consistency to plastic stage of consistency or vise versa.
From the points of view of determination of plastic limit is defined as minimum water content at which soil begins to crumble when rolled into the thread of 3 mm diameter.
Types of soil having plastic limit soil value expressed as percentage
1. Gravel-: Non plastic
2. Sand -: Non plastic
3. Silt -: 20-25
4. Clay (Alluvial soil) -: 25-50
5. Clay (Black soil) -: 200-250
Important point of plastic limit soil
1. Liquid limit and plastic limit almost coincides are of no significant for gravel and sand .
2. Liquid limit is higher than plastic limit for clays and silt
3. If Sand is mixed with the clay ,then liquid limit and plastic limit of clay reduces but,due to this reason comparatively reduction in plastic limit is less than the reduction in liquid limit, hence plasticity index also reduces.
What is plastic limit of soil?
Regarding this, “what is plastic limit of soil?”, a soil limit having minimum water content at the boundary between the plastic and semi-solid stages of consistency in which a soil will just begin to crumble when rolled into a thread of 3mm diameter and it’s water content expressed as a percentage of the oven dry soil.
Plastic limit of soil test
Plastic limit of soil test is a consistency which is widely used in overall the world and help to improve the prediction of soil identification and classification of soil.
Plastic limit of soil test is usually popular test that is determined by the two methods cone penetrations method and convention plastic limit test with the use of apparatus smooth glass surface, a container for determination of water content and oven in which procedure of plastic limit give the results of plastic limit and computer the plasticity index.
Plastic limit of soil range
Plastic limit of soil range -: loamy soil having clay ratio 0.30 to 0.40 is plastic limit varied from 20 to 25% and clay soils having clay ratio 0.75to 0.78 is plastic limit varied from 25to 30%.
Plastic limit of soil definition
Plastic limit of soil is defined as the minimum water content in which soil in plastic stage of consistency that is passes from semi solid stage of consistency to plastic stage of consistency or vise versa soil will just begin to crumble when rolled into a thread of 3mm diameter
Plastic limit of black cotton soil
Plastic limit of black cotton soil corespondent to engineering property is expressed as 40.6 Percentage and liquid limit is 86 percent and plasticity index is 45.4 percent, these are plasticity characteristics of black cotton soil.
Black cotton soil has a texture which consist the properties of like highly clay and highly plasticity that structure is cloddish and develops deep wide cracks when contract with in dry form.
Shrinkage limit-: it is denoted by Ws, it is defined as the minimum water content at which soil is still completely saturated
Shrinkage limit is defined as maximum water content below which only reduction in water content does not leads to the decrease in volume of the soil as water is being replaced by air if water content is reduced below shrinkage limit
Shrinkage limit of soil
shrinkage limit of soil passes from solid stage of consistency to semi solid stage of consistency and vise versa , in this consistency consist the water content at which the soil stops shrinking further and attains a constant volume, this type of consistency is less frequently used than the liquid and plastic limits.
What is shrinkage limit of soil
Regarding this, what is shrinkage limit of soil?”, its consistency is a test that describes the water content of a soil at which the soil stops shrinking further and attains a constant volume that is evaluates swelling and shrinkage properties of fine grained soil and also use for the design problems of structure which is resting on such soil and play a important factor to asses the stability of soil related construction materials such as design of dams, roads pavement, embankments and construction of foundation.
Plasticity index-: Plasticity index is the range of consistency within a soil behaviour of plastic properties is called plastic range and it’s indication is plasticity index.
Plastic index is a numerical difference between the liquid limit and the plastic limit of a soil.
Ip =Wl – Wp
Where, Ip is the plastic limit, Wl is the Liquid limit and Wp is the Plastic limit.
When the Plastic limit is equal to or greater than the Liquid limit ,the Plasticity index is reported as zero, Sandy soils should be firstly determined the plastic limit, when plastic limit can not be determined,the plasticity index is reported as Non plastic.
Consistency index- consistency Index is defined as the ratio of the liquid limit minus the natural water content to the plasticity index of a soil
Ic = Wl-W/Ip
Where, Ic is the Consistency Index, Wl is the Liquid limit and the Ip is the plasticity index.
Consistency index is a mostly useful in saturated fine grained soil study behaviour which is consist of a soil is equal to 1, it is at the plastic limit
Important points of consistency index
1. The soil with Ic equal to zero is its behaviour of liquid limit
2.The Ic is greater than unity the soil is in a semi solid state and will be stiff.
3. A negative consistency index behaves just like as liquid.
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Liquidity index – The Liquidity index is the ratio of the natural water content of a soil minus it’s plastic limit to its plasticity index as expressed as a percentage is called the Liquidity index.
IL= W- Wp /Ip
Where IL is the Liquidity index, W is the water content and Ip is the plasticity index.