As plasticity index is a product of these limits, consistency limits together with other indices including plasticity index, can be used to classify fine-grained soils to be used for engineering construction. This is thought to be very useful because as limit determination is relatively simple, it is more difficult to determine these other properties. Save my name, email, and website in this browser for the next time I comment. (PDF) Classification of Soils and Their Plasticity Index of the … The range of water content over which a soil has a plastic consistency is termed the Plasticity Index(I P or PI). The soil that have high activities are known as active clays which exhibits plastic behavior over a broad range of water content i.e. It is interesting to see that still consistency limits can be well connected with engineering properties of cohesive soils; this is due to some common set of factors that have influence on both consistency limits and engineering properties. When Ip and clay percentages of a group of soil is plotted, a straight line is obtained connecting origin. The plasticity of a given clay is depend on: (i) The nature of clay mineral (ii)The amount of clay mineral present. W Well graded L Low plasticity (wL<35%) P Poorly graded I Intermediate (3590%) Mixed soil plasticity index testing Yes Figure 1 Research Flow Chart Soil index properties test of natural soil: specific gravity test, water content test, grain size analysis Making test objects -Soils + Vermiculite 4% + Bledug Kuwu mud 5% Soils + Vermiculite 4% + Bledug Kuwu mud 10% In case of coarse grained soil liquid limit coincide with plastic limit and can be said that they cannot reach plastic state, that is Ip=0. If clay percentage of soil is changed artificially a relationship between plasticity index and clay percentage can be established. Photographs courtesy of Engineering Properties of Soils Based on Laboratory Testing Manual, Prof. Krishna Reddy, UIC, 2002. A cohesionless soil has zero plasticity index. At the same liquid limit, the higher the plasticity index, the more cohesive the clay. Such soils are termed non-plastic. Soils with a high PI have a higher clay content. Plasticity chart is extensively used in classifying fine grained soil. The relationship between fineness of kaolinite, illite, montmorillonite and plasticity index are presented above. form a ribbon of soil with thumb and index finger, about 1/2 inch wide and as long as possible. Among all consistency limits and indices, only shrinkage limit can be obtained from both disturbed or remolded and undisturbed soil. soil samples collected from various river valley projects were used in this study. But compressibility is found almost unchanged. Keywords – Compression Index, Plasticity Index When the soil is at its liquid limit, its liquidity index is 100% and it behaves as a liquid. How to Differentiate Shallow Foundation to Deep Foundation? Plasticity Index. The consistency of most soils in the ground will be plastic or semi-solid. A Learning Platform for the Civil Engineers. Photographs courtesy of Engineering Properties of Soils Based on Laboratory Testing Manual, Prof. Krishna Reddy, UIC, 2002. When we are discussing about plasticity index the focus will be the clay soils. This model has been discussed in this Research Paper. According to Skempton, volume change in soil under swelling and shrinkage is a function of clay fraction in the soil and plasticity index. • A lower plasticity index of two soil is indicative to have high organic matter in soil. Fill LL Device ~2/3 high with wet soil. Based on laboratory tests for several soils, Skempton (1953) made the observation that, for a given soil, the plasticity index is directly proportional to the percent clay-size fraction (i.e. Calculation shall be in accordance with AASHTO Method T-91 (Figure VI-19). same types of particles also found in mica and kaoline ( entirely or partially) but of relatively coarser size as compared with highly colloidal particles exist in plastic clays. What does plasticity index indicate? Besides this other soil classification system like AASHTO soil classification system, unified soil classification system uses plasticity index and liquid limit and grain size analysis to classify fine grained soils. It indicates the range of moisture content over which the soil can exhibit plastic properties. Inorganic fines; CL- Lean Clay-LL<50 & PI > 7 and plots on or ... plasticity chart to the left. NOTE:- When either w1or wp cannot be determined,then soil is non-plastic (NP) When P.L > L.L -> Plasticity index is reported as zero (on non- negative). What are Residual Soil and Transported Soil? Fat clays are highly plastic and possess a high plasticity index. What is Significance of Plasticity Index of Soil? We have all know more or less about plasticity chart this is nothing but a plot with plasticity index against liquid limit. b = Percentage of soil particles passing through No. Thus the Atterberg limits are not only used to identify the soil's classification, but it allows for the use of empirical correlations for some other engineering properties. A summary of the BSCS is shown in Table 1.1 and its associated plasticity chart in Fig. There is also a close relationship between the limits and properties of a soil such as compressibility, permeability, and strength. What is Recovery Ratio and RQD in Soil Sampling? Your email address will not be published. The plasticity index of the soil is the numerical difference between the liquid and plastic limits. From above figure the slope of the straight line is. The information regarding the type of clay in the soil may be obtained by considering the PI in relation to the LL. the soil. This parameter cannot be negative if plastic limit, in some exceptions, is larger than liquid limit, ignoring negative value, it is considered to be zero. The engineering concept of soil plasticity has evolved to explain why some soils are more failure prone than others. • Plasticity index in relation with liquid limit and sieve analysis will provide us valuable information for soil classification. The Casagrande plasticity chart has been used for more than 70 years to classify fine-grained soils in accordance with the USCS. The liquidity index is also known as Water-Plasticity ratio. Different straight line will be produced for different soils, as it is considered that two soils have same percentage of clay, they will have different constituent minerals. Your email address will not be published. Plasticity chart is extensively used in classifying fine grained soil. i.e. It indicates the fineness of the soil and its characteristics as regards plasticity and cohesiveness, i.e., its power to change shape without altering its volume. Thus plasticity index is a measure of fineness of particles. About 70% particles of bentonite is of colloidal size (look like scale or sheet) which is about 30 percent in common highly plastic clays. a = percentage of soil particles passing through No.200 or 0.074 mm sieve more than 35% but not more than 75%. 17. Negative values of the liquidity index indicate water content smaller than the plastic limit. Required fields are marked *. In case of zero value, soil are considered to have little/no clay or silt and called non-plastic soil. Porosity-Permeability Relationship of Concrete. We have all know more or less about plasticity chart this is nothing but a plot with plasticity index against liquid limit. 14.330 SOIL MECHANICS Soil Classification ASTM D4318-10 Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils. A soil is considered non-plastic when liquid limit or plastic limit cannot be determined and denoted by NP.Clay soils having high plasticity index with high liquid limit, is called highly plastic clays, sometimes called fat clays those have low values called lean or slightly plastic clays. A higher value of the group index means that the poorer the soil as subgrade material. • Plasticity index of soil depends chiefly on clay content in soil. Liquid Limit, Plastic Limit, and Plasticity Index of Soils ASTM D4318 – 17e1 Page 2 of 13 6.5 The composition and concentration of soluble salts in a soil affect the values of the liquid and plastic limits as well as the water content values of soils (see Test Method D4542). Run 4 Tests. Save my name, email, and website in this browser for the next time I comment. Soil has plasticity within a range of water contents and has considerable strength when air-dry. Plasticity index Ψ was adopted in order to evaluate the severity of asperity contacts or the running-in effects in lubricated rolling /sliding contact surfaces. Compaction Factor Test – Workability of Concrete, Retaining Walls – Types, Design, Stability, Concrete Curing – Methods – Curing of Concrete. • For a same liquid limit of two samples, when plasticity index is increased, permeability decreases whereas toughness and dry strength are increased. 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