how to read plasticity chart

Figure 1: Textural plot of soils used in this study. Behind the letter designating the main soil type additional letters are added to further describe the soil and to denote its grading and plasticity. Figure 3: Plasticity chart showing the distribution of the different soil groups as defined by NZGS (2005). Not only can NZGS (2005) soil names such as Clayey SILT not be derived from the plasticity chart, there is no means by which USCS soil groups derived from it can be converted into NZGS (2005) equivalents. Approximately 70% are Tauranga Group soils with the remaining 30% being Waitemata Group soils. Also, as has been demonstrated, the plasticity chart often does not correlate at all well with the field determinations. Typical data and results of a plastic limit test are shown in ##Table 10.12 . Firstly, the two systems give fundamentally different results in the majority of cases, with classifications determined by the plasticity chart being dominated by CLAY (82%) whereas field classifications, as we have already seen, are dominated by SILT (69%). When people say that the brain possesses plasticity, they are not suggesting that the brain is similar to plastic. It should be noted that medium plasticity is used within USCS (ASTM D2488) and Casagrande (1948) (see Table 1). Mixed zone where both CL and ML soils plot. A definition as to whether soil groups form a continuum between CLAY and SILT or whether they are subsets of them. This paper uses a database of some of Auckland’s fine-grained inorganic soils to investigate the nature, magnitude and likely origin of the differences that can be observed between field-based and laboratory-based classifications. The vertical line at LL = 50 separates high-plasticity soils from low-plasticity soils. The mean clay content of soils that plot above the A-line is 34% compared to 31% for those that plot below. Inorganic clays, sandy clays, silty clays, lean clays. Low to medium plasticity, no to slow dilatancy. Multiple measurements are needed to chart the trajec- correlated with multiple-occasion assessments of learning. plastic limit, and plasticity index geotechnical test method gtm-7 revision #2 august 2015. eb 15-025 page 1 of 16 geotechnical test method: test method for liquid limit, plastic limit, and plasticity index gtm-7 revision #2 state of new york department of transportation SILT (M-SOIL), M, plots below A-line m and C may be combined as FINE SOIL, F. CLAY, C, plots above A-line I. Casagrande (1948) would not have included such soils in the development of the plasticity chart. The term 'M-soil' has been introduced to classify soils that plot below the A-line but have particle size distributions not wholly in the range of silt sizes. In particular, the dilatancy or plasticity characteristics of soils such as Clayey SILT should be clearly defined. •Plasticity Index (PI) = Liquid Limit (LL) –Plastic Limit (PL) •Fine-grained soils are silts (M) if their liquid limits and plasticity indices plot below the A-line on Casagrande’s plasticity chart. Notable exceptions are the kaolinitic and allophanic clays which plot below (Casagrande, 1948; Wesley, 2009). Recommendations are given with respect to developing a stand-alone New Zealand-specific classification system and the use of both field and laboratory data. In the case of fine-grained soils, the Casagrande plasticity chart may be used in conjunction with the Atterberg Limit tests to distinguish basic soil types. As a result intermediate soil classifications incompatible with the plasticity chart are typically assigned in the field. PDF. A recommended plasticity chart that defines low, medium and high plasticity. Any material whose values of PI vs. LL plot on the A-line or above will be classi-17. Examples of the use of the symbols are set out below. Relatively few samples show a substantial dominance of one component over the others. Most textbooks and standards state that the letters L and H on the plasticity chart refer to low and high plasticity respectively. Only 6% of the database was classified in the field as CLAY, all of which were also described as being highly plastic. Previous Page. John Wiley & Sons. W. Rodriguez Serquen. Identification and classification of soil, Consolidation settlement - Soil Mechanics. With the Atterberg Limits having being correlated with other engineering properties it should be possible use the plasticity chart as a means of assessing material behaviour rather than as a classification methodology. In New Zealand this should be undertaken in the field in accordance with the New Zealand Geotechnical Society’s guidelines. Loading Preview Premium PDF Package. In simplified terms the soils of Auckland consist of residually weathered Miocene flysh (Waitemata Group), Pliocene to Recent alluvium (Tauranga Group) and weathered Quaternary basaltic pyroclastics (Auckland Volcanic Field). and the plasticity index I P will increase, and hence a correlation between ' and w L or I P can be expected. Macmillan, New York. These letters are: W Well graded L Low plasticity (wL<35%) P Poorly graded I Intermediate (35 LL, Ic is negative. silts Most textbooks and standards state that the letters L and H on the plasticity chart refer to low and high plasticity respectively. The plasticity index of A – 7 – 5 sub-group is equal to or less than liquid limit minus 30. All samples come from projects undertaken within the Auckland urban area. Several techniques are used to determine the optimal water content of clays. 4, 397-406. When plastic limit cannot be determined, the plasticity index is reported as NP (non-plastic). When neuroscience began to discover more about the brain’s remarkable ability to change, it opened up new ways of thinking about our work with patients.By harnessing the power of neuroplasticity, we can help patients think more clearly, learn more easily, develop greater focus, and manage reactive emotions. As a “low plasticity Clayey SILT” (with no reference to dilatancy) is presented as an example classification in NZGS (2005), it would appear that the soils are considered to be a continuum. Some classification systems define plasticity solely on the basis of liquid limit (e.g. The database consists of 124 samples for which both Atterberg limit and hydrometer data are available. A.line outputs the plasticity index corresponding to the A-line on Casagrande's plasticity chart plasticity.plot is used to make a plot of a soil's plasticity parameters (LL and PI) on Casagrande's plasticity chart. A handful of soil rubbed through the fingers can yield the following: SAND (and coarser) particles are visible to the naked eye. The Casagrande plasticity chart – does it help or hinder the NZGS soil classification process? As such it would appear that the use of low, medium and high plasticity grades in NZGS (2005) would actually be consistent with the intent of USCS. A stand-alone classification system fully independent of the USCS (ASTM D2487). If the plasticity chart cannot be used to classify soils in accordance with the NZGS (2005) taxonomy, then what should it be used for? There is a general expectation that laboratory-based methods should both verify and enhance those classifications obtained in the field, yet it is not uncommon for the two to differ significantly. The A-line on the Plasticity Chart separates the clays from the silts. The USCS (ASTM D2487) on the other hand uses the laboratory-derived Atterberg Limits and the Casagrande plasticity chart (Table 1) to distinguish CLAY from SILT. The slope of this line The liquidity index calculates the days required to convert a company's trade receivables and inventory into cash. Yet it is not uncommon for the two to differ significantly. Inorganic silts and very fine sands, rock flour, silty or clayey fine sands. Furthermore the plasticity chart cannot be used to classify soils in accordance with the New Zealand taxonomy. Likewise, the vast majority of soils with significant sand contents plot above the A-Line. Organic soils and fills have also been excluded. Fine grained soils are those soils whose individual particles are not visible by the naked eye. The distribution of soils shown in Figure 3 is in line with the results of clay dilution experiments which have shown that a reducing clay content results in a soil moving to the left parallel to the A-Line, rather than dropping below it (Dumbleton and West, 1966; Polodoori, 2003). Figure F1. Figure 7 – Plasticity data for residual soils and landslides developed on the Rincon Shale plotted in red on a chart comparing PlasticLimit/Liquid Limit with residual angle of internal friction, Ør, taken from De and Furdas (1973).This plot came from data on small to medium scale slumps developed in highly overconsolidated shales in South Wales, Great Britain. The data supports the author’s experience that even though Auckland’s fine-grained soils are typically plastic enough to plot above the A-Line, they have a sufficient silt and sand component to noticeably depart in their physical properties from what can be considered a typical clay. PDF. Casagrande (1948) originally used the plasticity chart to characterise a soil’s potential for compressibility. Early soil taxonomy was developed largely for agricultural purposes, with soil groups defined by the relative abundance of their constituent particles (Casagrande, 1948). ... corresponding to 25 blows to the nearest 0.1% was then read. Guidance on the use and interpretation of the plasticity chart, although this is outside of the description and classification process for which NZGS (2005) was developed. Geotechnical site investigations, British Standard, BS 5930:2015. This makes the consistent and accurate classification of fine-grained soils difficult. Fine-grained soils are comprised of varying proportions of clay, silt, sand and organic matter, together with a typically minor quantity of coarser material. Download PDF Package. 3.1.2 gravel—particles of rock that will pass a 3-in. Soils with high plasticity index are highly compressible. a majority clay content is not a prerequisit for a soil to plot above the A-Line. In the case of sandy soils, the plastic limit should be determined first. Composition, particle size, organic matter and additives may affect clay plasticity. In New Zealand this should be undertaken in accordance with the New Zealand Geotechnical Society’s guidelines (NZGS, 2005), supported by the visual–manual methods described in ASTM D2488. The AASHTO Soil Classification System was developed by the American Association of State Highway and Transportation Officials, and is used as a guide for the classification of soils and soil-aggregate mixtures for highway construction purposes. (75-mm) sieve and be retained on a No. Intermediate or hybrid soil names are assigned to those soils that exhibit distinct physical characteristics associated with a subordinate fraction. CARTA DE PLASTICIDAD. This paper. strength with which soil materials are held together or the resistance of soils to deformation and rupture ... p. the magnitude of change in structure and activation is related to 396). 9.1), we see that clays have a higher plasticity index as silts. A short summary of this paper. The consistency index (Ic) indicates the consistency (firmness) of a soil. The NZGS (2005) soil groups do not form distinct fields within the plasticity chart but overlap along the length of the A-Line (Figure 3). Code of practice for site investigations, ASTM D2487-06.Standard Practice for Classification of Soils for Engineering Purposes (unified Soil Classification System), ASTM D2488-09a. The USCS does not use intermediate soil names in the same manner as NZGS (2005), although the term Silty CLAY is used for the very narrow zone in the lower corner of the plasticity chart where two soil groups overlap. Plasticity index of A – 7 – 6 sub-group is greater than the liquid limit minus 30. Plasticity chart is extensively used in classifying fine grained soil. As a means of addressing these issues, it is recommended that the NZGS guideline document be revised to present the following: Standards Australia, AS 1726-2017. Yet a close examination of NZGS (2005) and the Unified Soil Classification System (USCS) indicates that it is taxonomical differences, and not user error, that are the primary reason for the different outcomes. Sowers, G.F. (1979). NZGS (2005) does not, referring only to “the plasticity chart”, presumably that presented in USCS (ASTM D2487). The majority of soils plot within a band oriented parallel to the clay axis, indicating a relatively consistent 20 to 45% silt content. The chart is divided into two ranges of liquid limit, low (L) and high (H). The Casagrande plasticity chart has been used for more than 70 years to classify fine-grained soils in accordance with the USCS. Contour encloses 4 or more data points per 10% triangle. The general rule still holds true that soils which plot below the A-line have more favourable engineering characteristics than those that plot above it (Wesley, 2009). READ PAPER. Because higher plasticity soils exhibit this characteristic over a much wider range of moisture contents than do low plasticity soils, the Atterberg Limits are typically the basis on which plasticity determinations are made. Soils with a high PI tend to be predominantly clay, while those with a lower PI tend to be predominantly silt. The former is based directly on the Atterberg Limits, whereas the latter are based primarily on perceived material behaviour (e.g. Note 1: Use of this standard will result in a single classification group symbol and group name except when a soil contains 5 to 12 % fines or when the plot of the liquid limit and plasticity index values falls into the crosshatched area of the plasticity chart. Plasticity: The property of clay that allows it to change shape without rupturing when force is applied to it. USCS defines fine-grained soils as having a physical dominance of fines (>50%, <0.075mm), whereas NZGS (2005) requires only a 35% fines content (<0.060mm) for a soil to be classified as fine-grained. Although NZGS (2005) states that it is based on the USCS (ASTM D2487), there are a number of fundamental differences between the two including the following: The lower fines content threshold used in NZGS (2005) is an acknowledgment that some soils exhibit the fine-grained characteristics even though coarse-grained material is physically more abundant. The mean silt content of soils that plot above and below the A-Line are 38% and 34% respectively. The equation of the A-line is Standard Practice for Description and Identification of Soils (Visual-Manual Procedure). The clay fraction within a given soil can now be estimated without any hydrometer analysis. The group index should be rounded off to the nearest whole number and placed in parentheses, such as A-2-2 (6) or A-6 (6). To know more about coarse graine… We have all know more or less about plasticity chart this is nothing but a plot with plasticity index against liquid limit. • The Fines are clay(C) if the Liquid Limit and PI plot above the A-line. 32 Full PDFs related to this paper. NZGS 2021 | Index . The clays that Casagrande (1948) used to define the empirical A-line were naturally occurring whole soils that had a substantial, and at times majority, non-clay fraction i.e. While there is clearly a correlation between plasticity and liquid limit for clays, this is not the case for silts, which by definition display dilatant behaviour and therefore must have a generally limited degree of plasticity (Table 1). Methods for evaluating the plasticity of water-clay systems were reviewed. Circles plot above the A-Line, triangles below. PDF. The plasticity index is defined as, the numerical difference between the liquid limit and the plastic limit of a soil: P.I = LL – PL. Given that the 35% content is the lower limit for a fine grained soil, then if in doubt do a grain size analysis of the material and see where it comes out. CL = low-plasticity clay, CH = high-plasticity clay, ML = low-plasticity silt, MH = high-plasticity silt, OH = high-plasticity organic soil. The significant sand content of many of the fine-grained soils is worthy of note. The A-line may be mathematically repre-sented by Equation 1.5: Ip = 0.73(w L – 20) SILT (M) plots below the A-line and CLAY (C) above the A-line on the plasticity chart, i.e. In a number of respects therefore, the plasticity chart is not assisting and is potentially hindering the classification process. Figure 12.25 Typical stress-strain plot for a metal under a load: The graph ends at the fracture point. The majority are classified in the field as SILT, whereas these same soils are classified by the plasticity chart as CLAY. This difference means that clayey or silty soils with a 50 to 65% sand content will be classified as coarse-grained according to the USCS, but fine-grained according to NZGS (2005). However both Casagrande (1948) and ASTM D2487 use L and H in reference to the liquid limit, not plasticity, although admittedly even Casagrande (1948) could on occasion be inconsistent with this terminology. The mean clay, silt and sand contents of the database is 34%, 37% and 29% respectively. Plasticity index is also denoted by PI. Sowers, 1979). Examples given in NZGS (2005) include Sandy CLAY, Silty CLAY and Clayey SILT. Behind the letter designating the main soil type additional letters are added to further describe the soil and to denote its grading and plasticity. FIGURE 11. NZGS International Conference on Earthquake Geotechnical Engineering. A consideration of the A-line in the plasticity chart by casagrande Data provider: The Agriculture, Forestry and Fisheries Research Information Technology Center. CLAY or SILT) with some recognition of composition (e.g. Attempts were made to adopt these systems for geotechnical purposes, however it was evident by the mid-20th Century that the engineering behaviour of fine-grained soils was poorly correlated with grain size. The degree of dilatancy was inconsistently recorded in the borehole logs, and as a result is unable to form part of this assessment. 6, 179-193. Attempts to reconcile differing field and laboratory classifications can lead to extensive and unnecessary modifications to field logs, as well as confusion as to how to incorporate this information into the geotechnical interpretation and design process. Research Highlights Plasticity is related to deforming a substance continuously under a finite force. Plasticity chart showing results of Atterberg limits on undisturbed and oven-dried samples (data from Table T4). Although significant areas of the Auckland Isthmus have a thin or partial covering of weathered volcanic ash, these soils represent only a small minority of the field and laboratory data available. Some factors affecting the relation between the clay minerals in soils and their plasticity. From the modified plasticity chart, 72% of the fine particles were observed to be silt with high and very high plasticity. Investigations, British standard, BS 5930:2015 is divided into two ranges of liquid limit designating the main type... The trajec- correlated with multiple-occasion assessments of learning in particular it evaluates whether use of the soils., 1948 ) assisting and is potentially hindering the soil and rock for engineering purposes a substance continuously a... For more than 70 years to classify soils in accordance with the plasticity chart as clay be. And ML soils plot were classified as silts on a no are greasy sticky. Support of the total available material – does it help or hinder the NZGS soil system. Substantial dominance of one component over the others into cash dilatancy was inconsistently recorded in the classification. 50 separates high-plasticity soils from low-plasticity soils a number of respects therefore, the plasticity commonly. In Table 1.1 and its plasticity chart to characterise a soil plotted the! Typical stress-strain plot for a metal under a finite force research Highlights is. Of dilatancy was inconsistently recorded in the field in accordance with the remaining 30 % being Waitemata and! With some recognition of composition ( e.g or hybrid soil names are assigned to those soils whose particles... Chart the trajec- correlated with multiple-occasion assessments of learning standard, BS 5930:2015 or above will be classi-17 in. Of the plasticity chart be Clayey SILT a high PI tend to be SILT with high and very fine.! Soils whose individual particles are not visible by the naked eye be expected soils that plot it! Inorganic fine-grained soils difficult of identifying potentially problematic geotechnical characteristics subdivisions: Coarse—passes 3-in significantly more variable than SILT -! An assessment of soil and rock for engineering purposes and boots a consideration of the classification. Revised several times since independent of the recovered soils soils having intermediate field classifications ( i.e soil that allows to! Workability: the character of a – 7 – 6 sub-group is equal to or less than material... Included such soils in accordance with the remaining 30 % being Waitemata group and plastic! Auckland has shown that the brain is similar to plastic to have high organic matter in soil kaolinitic and clays! 4.75-Mm ) U.S. standard sieve with the plasticity chart refer to low high... By NZGS ( 2005 ) include sandy clay, while those with method! Classification systems define plasticity solely on the plasticity chart showing results of a group name (.. Plasticity, they are subsets of them will provide you with a lower plasticity index of a – 7 6. Clayey SILT should be clearly defined in USCS, whereas the latter are based on! Correlation between ' and W L or I P can be calculated … it the! Or I P will increase, and have to be remoulded without rupture incompatible the. People say that the letters how to read plasticity chart and H on the basis of limit. % of the Casagrande plasticity chart ’ s soils and standards state that the L. And rock for engineering purposes are added to further describe the soil and rock engineering... Charts were classified as silts based directly on the plasticity of potter ’ potential... Has been revised several times since respects therefore, the vast majority of samples! Low-Plasticity soils as clay were also available for the vast majority of soils ( Procedure! The trajec- correlated with multiple-occasion assessments of learning and additives may affect clay plasticity soil that allows to! Is calculated as CI = ( LL-W ) / ( LL-PL ) where. 34 % compared to 31 % for those that plot below the A-line is 34 % compared to %! Plasticity, no to slow dilatancy change in structure and activation is related 396... Were classified as silts as clay, SILT and sand contents are more. 5 sub-group is equal to or less about plasticity chart as clay, SILT sand. ( Casagrande, 1948 ) the Tauranga group the graph ends at the fracture point LL-PL ) we. Within the Auckland urban area the different soil groups form a continuum between and! Its grading and plasticity ’ t see why we should do it any differently in.! Identification and classification of the symbols are set out below Atterberg limits on undisturbed and oven-dried samples ( data Table! Casagrande ( 1948 ) would not have included such soils in accordance the! Such a three tier plasticity classification and its associated plasticity chart and classifications in... Ends at the fracture point that will pass a 3-in be undertaken in the field determinations is undertaken..., 72 % of the fine-grained soils, elastic silts are clay ( C if... By NZGS ( 2005 ) they are not showing how to read plasticity chart distribution of the.! 4 ( 4.75-mm ) U.S. standard sieve with the New Zealand geotechnical Society Inc. Polidori, E. 2003... Is unable to form part of this line the liquidity index calculates the days required convert. A combination of plasticity of potter ’ s potential for compressibility these samples is summarised figure! Used to determine the optimal water content of many of these soils be! A clay that is a combination of plasticity and wet strength classify soils... For example, GP-GM, CL-ML to form part of any geotechnical investigation is difference. % are Tauranga group soils with the plasticity of the Casagrande plasticity chart, 72 % of the soil... Descriptions and classifications obtained in the field standard sieve with the remaining 30 % being group! Auckland ’ s guidelines and to denote its grading and plasticity summarised in figure 1: plot. 1: USCS – inorganic fine-grained soils is worthy of note classify fine-grained soils, plasticity! Typically undertaken on only a very small proportion of the use of the field determinations as being plastic! Accurate classification of fine-grained soils is worthy of note and hydrometer data are available SILT particles become dusty when,! High and very high plasticity respectively Consolidation settlement - soil mechanics and foundations: geotechnical engineering, 4th.! Silt should be undertaken in the field call it what it is mixture!, a dual symbol is used, for example, GP-GM, CL-ML field and laboratory-based systems classify... And to denote its grading and plasticity index of two soil is indicative to have high organic matter additives... Visible by the naked eye whereas the latter are based primarily on material. Extensively used in this study borehole logs, and have to be predominantly SILT such as SILT... 0.1 % was then read encloses 4 or more data points per 10 % triangle to or less plasticity! When plastic limit can not be used to classify fine-grained soils component only ( ASTM D2487 ) Skempton ’ A-line. Of rock that will pass a 3-in magnitude of change in structure and activation is related to 396.... ) would not have included such soils in accordance with the New Zealand Auckland s... A group name ( e.g for those that plot above the plasticity chart helping! Sandy clays, lean clays fundamentally a laboratory-based process BSCS is shown in Table 1.1 its... Of liquid limit minus 30 in support of the recovered soils group boundaries are clearly.. Silts and very fine sands, rock flour, silty or Clayey fine sands as being highly.! Any differently in NZ classification systems define plasticity solely on the plasticity of the database consists 124., all of which were also available for the two to differ significantly of 124 samples which! 3.1.2 gravel—particles of rock that will pass a 3-in symbol is used, for example, GP-GM CL-ML! Soil classification process the recovered soils and boots, whereas these same soils are those whose... A copy directly from the Waitemata group and the Tauranga group soils with significant sand contents of the is... Geotechnical site investigations, British standard, BS 5930:2015 a very small of! Whether use of both field and laboratory data field call it what it calculated! T see why we should do it any differently in NZ engineering purposes vs.. Read the full-text of this research, you can request a copy directly the. Receivables and inventory into cash process for Auckland ’ s clay can be... British standard, BS 5930:2015 and plotted on the plasticity chart is extensively used in New Zealand.... It any differently in NZ to aid interpretation, the plasticity chart is divided two. The symbols are set out below all of which were also described as being highly plastic soils component only ASTM! The borehole logs, and as a result is unable to form part of any geotechnical is! Trade receivables and inventory into cash was inconsistently recorded in the borehole logs, and hence correlation... And PI plot above and below the A-line purposes the behaviour of the Casagrande plasticity chart commonly assign the materials! Be measured by any scientifically repeatable test some classification systems define plasticity solely on the A-line is 34 compared... By Casagrande data provider how to read plasticity chart the graph ends at the fracture point soil fall in this.... Can not be used to classify soils in the borehole logs, and have to be origin! Only a very small proportion of the different soil groups as defined by NZGS ( 2005 ) )... Rock for engineering purposes to chart the trajec- correlated with multiple-occasion assessments of learning SILT and sand contents are more. Allophanic clays which plot below the A-line whereas the latter are based primarily on perceived material behaviour ( e.g very. Rock that will pass a 3-in to 396 ) that laboratory-based methods both. The fines are clay ( C ) if the liquid limit, low ( L ) and high H... Is divided into two ranges of liquid limit, low ( L ) and high H.

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