Relationship between plasticity index and liquid limit

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relationship between plasticity index and liquid limit

The numerical difference between the Liquid Limit and Plastic Limit is termed the the Liquid Limit (LL) of such soils is , and the Plasticity Index (PI). On the basis of the liquid limit and the plastic limit, the plasticity index (PI) can be defined as the numerical difference between them: PI = LL - PL. The plasticity. the plastic limit of montmorilloniteÀ(illite)Àkaolinite. The same conclusion was traced later by Mitchell (). Several attempts to link plasticity index with liquid.

The liquid limits of the samples ranged from The average void index at liquid limit [IvL ave ] of the As stated before at plastic limit [IvP ave ] was found to be—0. Insertion the liquid limits and the plastic limits were determined by of these values in Fig. It shows that when water content is The void ratio e against log of pressure log P rela- normalised as liquidity index, all remoulded soil test results tionship of the soils tested has been found to be approxi- plot in a narrow band which can be fitted with a linear mately linear.

Using this linear relationship and taking equation of the form effective consolidation pressures at liquid limit and plastic limit as 6. Figure 2 shows the The practical advantage of using Eq. The equation of the narrow band P curve for reconstituted soils can be predicted with rea- can be fitted with a linear equation of the form sonable accuracy without having to conduct any consoli- dation test.

It is observed from there is good agreement between the predicted and the Figs. Figure 5 further shows the good as generalising parameters. The line generated by Eq.

There is unity the consolidation pressure is 6.

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Similarly, at slight disagreement near the plastic limit range for the red plastic limit liquidity index zerothe consolidation pres- soil. The data of the present study have also been plotted in Youssef et al. Fig- data on eight soils as well as by data from skempton [10] ure 3 shows the plot of void index IV against log P. It is and from other data on remoulded clays that the void ratio apparent that the ICL of the present study coincides with corresponding to the plastic limit was reached at effective Author's personal copy Indian Geotech J Fig.

The agreement plastic limit of the soils. The Casagrande method for between theoretical derivation and experimental verifica- determination of the plastic limit which is the most com- tion means that a hundred fold increase in effective con- monly used method is prone to human error [1]. In the solidation pressure from liquid limit to plastic limit is well present work plastic limit was determined from defined founded and can therefore be accepted. Further it has been observed that any small obtained from the experimental results.

This is shown in error in the determination of plastic limit by thread rolling Fig. A close agreement was found between the two sets method would lead to a large error in the evaluation of of results with the errors ranging from?

relationship between plasticity index and liquid limit

The compression index Cc of a soil is usually defined In the above discussions it has been brought out that in terms of the negative slope of the e—log P plot and this consolidation pressures at both liquid limit and plastic limit slope is obtained as are uniquely related. Wroth [14]; Nagaraj et al. Furthermore, the compression index Cc has been found to be an exclusive function of plasticity index and soil specific gravity, the equation being identical with that derived from critical state theory by Wroth and Wood [13].

relationship between plasticity index and liquid limit

A pressure—void ratio equation derived in terms of void ratios and consolidation pressures at liquid limit and plastic limit formed a basis for prediction of void ratio as a function of consolidation pressure without carrying out any consolidation test. This findings can be said to be true only Fig. If the strength at liquid limit References and plastic limit are 1.

What is Significance of Plasticity Index of Soil?

As unique relation plastic limit of cohesive soils. Mater Res Stand 3 9: Burland JB On the compressibility and shear strength of between liquid limit and plastic limit is not possible, it leads natural clays 30th Rankine lecture.

Prediction of limited soils which may behave like this. Hence the above of soil behaviour. Development of a generalised approach. Ind findings of unique consolidation pressures at liquid and Geotech J 20 4: Part Saturated uncemented soils. Indian Geo- soils plotting above the A line in the plasticity chart.

VL18 Soil Plasticity

Ana- Conclusions lysis and prediction of soil behaviour. Wiley Eastern Limited, India 6. The plastic limit is defined as the moisture content where the thread breaks apart at a diameter of 3.

A soil is considered non-plastic if a thread cannot be rolled out down to 3. Liquid limit[ edit ] Casagrande cup in action The liquid limit LL is conceptually defined as the water content at which the behavior of a clayey soil changes from plastic to liquid. However, the transition from plastic to liquid behavior is gradual over a range of water contents, and the shear strength of the soil is not actually zero at the liquid limit.

The precise definition of the liquid limit is based on standard test procedures described below. A groove was cut through the pat of clay with a spatula, and the bowl was then struck many times against the palm of one hand. Casagrande subsequently standardized the apparatus and the procedures to make the measurement more repeatable. Soil is placed into the metal cup portion of the device and a groove is made down its center with a standardized tool of 2 millimetres 0.

The number of blows for the groove to close is recorded. The moisture content at which it takes 25 drops of the cup to cause the groove to close over a distance of The test is normally run at several moisture contents, and the moisture content which requires 25 blows to close the groove is interpolated from the test results.

It is based on the measurement of penetration into the soil of a standardized cone of specific mass. Although the Casagrande test is widely used across North America, the fall cone test is much more prevalent in Europe due to being less dependent on the operator in determining the Liquid Limit.