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DIVISION S-5-PEDOLOGY

Relationship of Map Unit Variability to Shrink–Swell Indicators

^a Dep. of Crop and Soil Environmental Sciences, Virginia Polytechnic Inst. and St. Univ., Blacksburg, VA 24061-0404 USA
^b Dept. Comm Dev. Fauquier County, VA USA

pthomas{at}vt.edu

	ABSTRACT

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
A study was conducted in the Culpeper Basin in northern Virginia to quantify soil shrink–swell indicators, to relate the indicators to soil properties, and to partition variability into map unit components. Five delineations in each of five map units were selected for study. Three profiles were sampled within each delineation to complete a nested sampling scheme. Three map units of smectitic, high shrink–swell soils with phase names of Haymarket silt loam, Jackland silt loam, and Waxpool loam, all 0 to 2% slopes, were selected. Also selected was a vermiculitic, high shrink–swell soil map unit named Kelly silt loam, 0 to 2% slopes, and a kaolinitic, a low shrink–swell soil map unit named Davidson clay loam, 2 to 6% slopes, eroded. The Bt horizons of Haymarket, Jackland, Waxpool, and Kelly were clayey and had high cation-exchange capacities (CECs), liquid limits, and plasticity indices (PIs). Soils in the Davidson map unit also had high clay contents but had lower swell indices, liquid limits, PIs, and CECs than the other four map units. Shrink–swell indices and related soil properties exhibited high variability. However, the variability was partitioned within the delineations of each map unit. Each delineation within an individual map unit consisted of the same variability as map units with similar names. Swell indices in all five map units were correlated with liquid limit, clay content, and CEC. However, individual map units exhibited differing relationships. Liquid limit and clay content were the best predictors of swell index in the Haymarket, Jackland, and Waxpool map units, whereas clay content was the best predictor in the Kelly and Davidson map units. Cation-exchange capacity was weakly correlated with swell index in all five map units.

Abbreviations: ANOVA, analysis of variance • CEC, cation-exchange capacity • PI, plasticity index

	INTRODUCTION

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
CHANGES IN LAND USE in rapidly urbanizing areas, such as the northern Virginia counties adjacent to Washington, DC, continue at a rapid pace, increasing the competition for remaining undeveloped land areas. Much of the land has already been converted from rural farmsteads and woodlands to subdivisions or has been designated as prime agricultural land, thus protecting it from further development. This leaves the marginally adequate lands (soils) for further use. These soils are marginal for development because of soil properties, such as slow percolation rates for on-site wastewater disposal, or because they have significant amounts of clays that are conducive to shrink–swell tendencies. To complicate matters, soil map units identified in soil survey reports are composed of more than one kind of soil, the proportions of which are variable due to natural complexity of soil parent materials. Nonetheless, such soils are being converted to nonagricultural uses as sewer and water services are extended into once rural areas. Expansive soils, or soils with high shrink–swell potential, comprise extensive acreage in several counties in the Culpeper Basin in northern Virginia.

Identification and location of soils for site assessment are best accomplished by consulting a detailed soil map. Further detailed evaluations are a logical strategy for the specific siting of facilities such as houses, foundations, roads, or septic absorption fields. During the updating process of the Fauquier County (Virginia) Soil Survey, individual soil map units were examined extensively, with specific studies designed to identify variability and appropriately partition the variability into pedons, delineations, or map units. In addition to variability assessments, soil properties have been quantified by map unit during the update process. Some of these properties may contribute to shrinking and swelling in high shrink–swell soils.

Soil variability compounds interpretation of a map unit for a specific use. Identification and quantification of spatial variability of soil properties in map units are needed to make accurate soil and land use interpretations. Map unit variability can be evaluated by several statistical methods, including analysis of variance (ANOVA), geostatistics, and coefficients of variability. No one procedure is recommended over another; the study design depends on time constraints, efficiencies, needs, and objectives of the user and investigators. Analysis of variance can be used to evaluate map unit composition and variability in a typical second-order soil survey as it allows the study of the spatial aspect of variability with reduced numbers of samples (Wilding and Drees, 1983). Nested ANOVA has been employed in several map unit studies (Wilding et al., 1965; Edmonds et al., 1985; Thomas et al., 1989). These studies allowed for the partitioning of variability into map units, delineations within map units, pedons within delineations, and profiles within pedons. Studies evaluating variability of crop yields and soil properties in map units have found variability to be as great within map units as between map units (Edmonds et al., 1985; Thomas et al., 1989; Karlen, et al., 1990). Variability within map unit delineations is often greater among delineations of the same map unit (Wilding et al., 1965). However, variability within delineations has been observed to be greater than variability between delineations (McCormack and Wilding, 1969) possibly due to complex parent materials, landscape variability, aspect, or other factors that cannot be delineated at the mapping scale.

Volume change in shrink–swell soils is related to the properties of the clay fraction. Studies to estimate clay fraction properties such as PI, clay content, specific surface area, and clay mineralogy have identified these properties as the most common indicators (predictors) of potential volume change. In soils dominated by illite, clay content is as reliable in predicting swelling potential as are the Atterberg limits (McCormack and Wilding, 1975). In a study of 12 southern soils with a variety of clay mineralogical suites from montmorillonitic, to mixed systems, to soils dominated by kaolinite, CEC was the soil property most correlated with mechanical strength and shrinkage of clods (Gill and Reaves, 1957). Clay content and specific surface area were highly correlated with coefficient of linear extensibility in micaceous and kaolinitic soils in Ontario, Canada and less correlated with montmorillonitic soils (Ross, 1978). In a study of montmorillonitic soils in Alabama, Karathanasis and Hajek (1985) found that smectite content was the only consistent soil property that significantly correlated with laboratory-measured shrink–swell potential.

The objectives of this study were (i) to make quantitative estimates of shrink–swell indices and soil properties, (ii) to partition variability into map unit components, that is, among map units, between delineations within a map unit, and between profiles within a delineation, and (iii) to determine the best predictors or indicators of shrink–swell potential.

	Materials and methods

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
Geology
The study area is within the Culpeper Basin region of southern Fauquier County, Virginia (Fig. 1) . The Culpeper Basin was formed in the late Triassic period (200 million years ago) when the paleocontinent, Pangea, began splitting apart. This splitting or rifting formed basins from present-day Canada to South Carolina. Sediments filled the Triassic Basins upwards to thousands of meters thick. The sediments lithified into brown and maroon sandstones and shales. During the Jurassic, volcanic activity occurred and extensive intrusions of igneous dikes were thrust upward through the sedimentary rocks. Much of this igneous material cooled into diabase, a medium-grained basalt. These dikes formed low ridges in the otherwise subdued basin landscape and are generally oriented in the present-day southwest to northeast direction. The heat from the igneous intrusions "baked" surrounding sediments, forming thermally altered shales that surround the diabase dikes (Froelich and Gottfried, 1988). Soils formed on these two parent materials have high clay contents and appreciable amounts of smectite (montmorillonite) and vermiculite.

View larger version (26K): [in this window] [in a new window]   Fig. 1 Study area in Culpeper Basin, Fauquier County, Virginia. Thermally altered shales surround diabase dikes

Study Design
The soil survey of Fauquier County (USDA-SCS, 1956) is currently being updated. Five delineations in each of the five map units were randomly selected from Fauquier County soil survey maps. Three sites (profiles) within each delineation, a total of 15 profiles within each map unit, were randomly located in a two-level nested sampling scheme. Morphological descriptions were made and series named at each site (profile) to initially assess map unit composition and variability. The control section of the argillic (Bt) horizon was bulk sampled for physical, chemical, and mineralogical analysis. The argillic horizon occurs at the depth at which foundations are typically installed (45–90 cm).

Laboratory Analysis
Samples were air dried, ground, and sieved to remove coarse fragments >2 mm. Laboratory analyses include particle-size distribution, CEC, Atterberg limits, potential volume change (PVC), and clay mineralogy. Particle-size distribution was accomplished by the pipette method (Gee and Bauder, 1986) and CEC by the sum of cations method (NH₄OAc, pH 7, and BaCl₂-TEA, pH 8.2) (Thomas, 1982). Atterberg limits (liquid limit, PI) were measured by ASTM method D4318 (American Society for Testing and Materials, 1993). Potential volume change was determined by the method of Lambe (1960). Shrink–swell potential was determined on each sample on the basis of PVC data. Mineralogical analysis was performed on the <2-µm fraction from control sections from one typifying pedon from each map unit. Free Fe oxides were removed with dithionate-citrate-bicarbonate (Mehra and Jackson, 1960). A preliminary study on selected samples was conducted to ascertain if smectite could be isolated from the medium clay fraction (<0.2 µm) on x-ray diffraction patterns. We were unable to accomplish this and abandoned the fractionation procedure. Sand was removed by sieving and the clay fraction was separated from silts by centrifugation and decantation (Jackson et al., 1950). Oriented mounts of the clay fraction were prepared by the method of Rich (1969) and saturated with KCl and MgCl₂-glycerol (Whittig and Allardice, 1986). Clay minerals were determined with a Scintag XDS 2000 x-ray diffractometer (Scintag, Santa Clara, CA) with Cu-K radiation and quantified by determining peak areas.

Statistical Analysis
Descriptive statistics of mean, minimum and maximum values, and coefficient of variability were estimated by the UNIVARIATE procedure (SAS Institute, 1985a). Observations (Y_ijk) (e.g., clay percentage, CEC, liquid limit) in the map units were described by the linear model

where µ represents overall mean, M_i represents the effect due to a particular map unit, D_ij represents the effect due to a particular delineation, and _ijk represents variation among the profiles within a given delineation and errors in sampling and laboratory procedures.

The SAS ANOVA procedure (SAS Institute, 1985b) was used to evaluate statistical differences between delineations and among map units for the measured soil properties. Percentage of the total variance contributed by each component in the sampling scheme was estimated by dividing variance contributed by the individual components by total variance. Stepwise regression techniques of SAS STEPWISE (SAS Institute, 1985b) were used to isolate the soil properties significantly correlated with swell index.

	Results and discussion

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
Variability of Shrink–Swell Indicators
For clarity in the following discussions, shrink–swell terms are defined. Shrink–swell indicators are soil properties, such as clay content and mineralogy, that directly or indirectly contribute to shrink–swell tendencies. Shrink–swell potential refers to the USDA-NRCS definition of low (<81 kPa), moderate (81–153 kPa), high (153–225 kPa), and very high (>225 kPa) classes (Soil Survey Staff, 1993). Shrink–swell potential is typically measured by the coefficient of linear extensibility (COLE) procedure (Soil Survey Staff, 1996); however, other direct measurements have used the same classification system, for example swell index. Swell index is a quantitative measurement of shrink–swell potential via PVC meter (Lambe, 1960) and was used extensively by the Federal Housing Administration in assessing home sites.

The Bt horizons of the soils in the Haymarket, Jackland, Waxpool, and Kelly map units were, on average, clayey with high or very high swell indices, and had moderate to high CECs, liquid limits, and PIs (Table 1) . Furthermore, the clay fractions of the Haymarket, Jackland, and Waxpool map units were dominated by smectite, whereas the clay fraction in the Kelly map unit was dominantly vermiculite (Table 2) . The soils in the Davidson map unit, although having similar clay contents, had significantly lower swell indices, liquid limits, PIs, and CECs compared with the other four map units, as expected from a kandic soil (Table 1). Additionally, kaolinite was the dominant clay fraction mineral (Table 2).

Average CEC for the smectitic Haymarket, Jackland, and Waxpool map units and the vermiculitic Kelly was significantly higher compared with the kaolintic Davidson CEC (Table 1). Jackland had the highest CEC, a reflection of the high clay content, coupled with large amounts of smectite. Variability of this property was less than variability of other measured soil properties, except for liquid limit. Given a correlation between clay content and dominant clay mineral species, CEC may be estimated in the field.

Atterberg limits are measurements of plasticity of a soil at specified moisture contents. Liquid limit is the moisture content at which a soil changes from a plastic body to a viscous liquid and begins to flow. Plastic limit is the lowest moisture content at which a soil can be deformed and maintain its shape without cracking. The difference between liquid limit and plastic limit is the PI, or a measure of a soil's potential plasticity, and is widely used in the geotechnical community to assess shrink–swell potential. Soils with high PIs are considered to have the capacity for expansive behavior. Liquid limit was highest in the Jackland map unit, followed by Waxpool, Kelly, Haymarket, and Davidson (Table 1). The high liquid limits were partially a reflection of the higher clay contents, but were best explained by the expanding 2:1 minerals, smectite and vermiculite (Table 2). Typically, the greater the specific surface area, the greater the total amount of water required to satisfy conditions at the liquid limit. Given that water adsorption is the same for all surfaces, expanding 2:1's, with more internal surface layers, adsorb more water and thus have higher liquid limits (Mitchell, 1993). Plasticity index followed the same trend as liquid limits for the map units. Plasticity index was significantly higher in Jackland, Waxpool, and Kelly than in Davidson and Haymarket. Soils with high layer charges (2:1 clays) can retain plasticity at lower moisture contents. Variability in both liquid limit and PI was large in all map units; thus, the dissimilar inclusions of low liquid limit and low PI soils will affect site suitability.

Swell index was not significantly different between the smectitic Waxpool and Haymarket soils and the vermiculitic Kelly soils (Table 1). The Davidson soils had significantly lower swell indices than the other four map units. The swell index for the Jackland map unit was significantly higher compared with the other map units, but exhibited the greatest variation in swell index ranging from a low of 115 kPa (2300 lbs ft^-2) to almost 600 kPa (12500 lbs ft^-2). The Jackland and Waxpool soils had swell index of very high and the Kelly, Haymarket, and Davidson soils had high swell indices. Each map unit had potential ratings ranging from moderate to very high (Table 1). Again, variability of this direct shrink–swell estimator was large within each map unit as reflected in both minimum and maximum values and in the coefficient of variability.

Shrink–swell indicators and postulated behavior were similar when comparing averages among the five map units, but pedons within the map units were dissimilar based on variability. This wide difference in all shrink–swell indicators emphasizes the need for reliable estimates of map unit composition and variability to accurately predict the probability of encountering expansive soils.

Map Unit Composition
All profiles in each of the five map units were classified on the basis of morphological descriptions and laboratory data in accordance of the procedures of the National Cooperative Soil Survey (Soil Survey Staff, 1993). Criteria employed in delineating taxonomic units in the map units were depth to bedrock, family particle-size class, base saturation, matrix color, and drainage class. Dissimilar inclusions differ appreciably by one or more properties and the differences are great enough to affect use and management (Soil Survey Staff, 1993). All map units, except Davidson, were dominated by soils other than the named series, but the inclusions had similar use and management interpretations. Davidson was the purest map unit in terms of named series, with half the profiles classifying as Davidson (Table 3) . Haymarket and Waxpool map units contained the greatest percentage of dissimilar inclusions. Dissimilar inclusions in the high shrink–swell Haymarket, Jackland, Waxpool, and Kelly map units would consist of soils with more favorable shrink–swell properties. For other use and management decisions, such as row crop production, inclusions of better soils would not be a detriment. However, for siting a home, contrasting soils could be as detrimental to a foundation as a high shrink–swell soil.

On the average, Jackland, Waxpool, and Kelly soils would be rated as having high shrink–swell soils but are commonly mapped with areas of low to moderate shrink–swell potential. This is critical in siting a home. We do not want one corner of the house on low shrink–swell material and another corner on high shrink–swell soils. Differential shrinking and swelling of the two contrasting materials could potentially cause as much or more damage than siting a home on a uniform high shrink–swell soil unless special engineering designs for each site are employed. Such examples are specially designed reinforced foundations, grading, guttering, and landscaping that moves water away from the foundation. Thus, in areas of high soil variability, a detailed on-site investigation seems prudent for any map unit containing high shrink–swell soils.

Prediction of Swell Index
Given statistically significant variability in the shrink–swell indicators, is there a relationship between the more easily measured soil properties that can be used to estimate shrink–swell potential? Correlation and regression are useful statistical techniques for both identifying related variables and for modeling and predicting the relationship between the same variables. In this study, correlation was used to isolate soil properties significantly related to swell index. Correlation techniques compare individual variables with one another and calculate estimates of the strength, or magnitude, of the statistical relationship. Correlations of selected soil properties for all soils and soils in individually named map units are given in Table 5 . Swell index, a direct measurement of shrink–swell potential, was correlated against four indirect indicators of shrink–swell potential: liquid limit, PI, clay, and CEC. The higher the number, the stronger the correlation.

Liquid limit, clay content, and CEC were the best predictors of swell index when all five map units were examined as one population (Table 5). However, when evaluating individual map units, CEC was weakly correlated with swell index in the Kelly and Haymarket map units and uncorrelated in the Jackland, Waxpool, and Davidson map units (Table 5). Liquid limit and clay content both correlated with swell index in all five map units but at different magnitudes. Liquid limit was the best predictor for the Bt horizons in the Haymarket, Jackland, and Waxpool map units. These three soils comprised a catena with diabase saprolite parent material and were dominated by smectite in the clay fraction. Swell index in the Davidson and Kelly map units was best explained by clay content. Smectite comprised a small portion of the clay fraction relative to the amounts of kaolinite in the Davidson and vermiculite in the Kelly.

	Conclusions

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
The Bt horizons of the soils in the high and very high shrink–swell Haymarket, Jackland, Waxpool, and Kelly map units were clayey and had high CECs, liquid limits, and PIs. The soils in the lower shrink–swell potential Davidson map unit, although having similar clay contents as the soils in the other map units, had significantly lower swell indices, liquid limits, PIs, and CECs than the other four map units.

Variability of the shrink–swell indices and related soil properties was high in all map units. Variability of the soil properties translates into variability of series in the map units. Named series in the high or very high shrink–swell map units comprised less than one-fourth of the map unit. Similar series, or inclusions, comprised the majority of these map units. Dissimilar inclusions could adversely affect foundations if a home is sited on both low or moderate and high or very high shrink–swell soils.

Although there was extreme variability in the map units, the variability occurred within the delineations of each map unit. Each delineation within an individual map unit consisted of the same variability.

Liquid limit, clay, and CEC were the best predictors of shrink–swell potential when all five map units were examined as one population. However, when evaluating individual map units, CEC was only weakly correlated with swell index in the Kelly and Haymarket map units and uncorrelated in the Jackland, Waxpool, and Davidson map units. Liquid limit and clay content were the best predictors of swell index in the Haymarket, Jackland, and Waxpool map units. Clay content was the best predictor in the Davidson and Kelly map units. Soil property variability in the map units was proposed to be related to clay mineralogy, where high smectite contents had a great influence on liquid limit in the diabase-derived map units.

Received for publication July 2, 1998.

	REFERENCES

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 

• American Society for Testing and Materials. 1993. Annual book of ASTM standards. Construction. Section 4. Soil and rock; dimension stone; geosynthesis. Vol. 04.08. ASTM, Philadelphia, PA.
• Edmonds W.J., Baker J.C., Simpson T.W. Variance and scale influences on classifying and interpreting soil map units. Soil Sci. Soc. Am. J. 1985;49:957-961.[Abstract/Free Full Text]
• Froelich, A.J., and D. Gottfried. 1988. An overview of early Mesozoic intrusive rocks in the Culpeper Basin, Virginia and Maryland. p. 151–164. In Studies of the early Mesozoic basins of the eastern U.S. U.S. Geol. Surv. Bull. 1976. U.S. Gov. Print. Office, Washington, DC.
• Gee G.W., Bauder J.W. Particle-size analysis. In: Klute A., ed. Methods of soil analysis. Part 1, 2nd ed Madison, WI: ASA and SSSA, 1986:383-411 Agron. Monogr. 9..
• Gill W.R., Reaves C.A. Relationships of Atterberg limits and cation-exchange capacity to some physical properties of soil. Soil Sci. Soc. Am. Proc. 1957;21:491-494.
• Jackson M.L., Whittig L.D., Pennington R.P. Segregation procedure for the mineralogical analysis of soils. Soil Sci. Soc. Am. Proc. 1950;14:77-81.
• Karathanasis A.D., Hajek B.F. Shrink–swell potential of montmorillonitic soils in udic moisture regimes. Soil Sci. Soc. Am. J. 1985;49:159-166.[Abstract/Free Full Text]
• Karlen D.L., Sadler E.J., Busscher W.J. Crop yield variation associated with Coastal Plain soil map units. Soil Sci. Soc. Am. J. 1990;54:859-865.[Abstract/Free Full Text]
• Lambe T.W. The character and identification of expansive soils. Washington, DC: U.S. Gov. Print. Office, 1960 Fed. Housing Admin. Rep. 701..
• McCormack D.E., Wilding L.P. Variation of soil properties within mapping units. Soil Sci. Soc. Am. Proc. 1969;33:587-593.
• McCormack D.E., Wilding L.P. Soil properties influencing swelling in Canfield and Geeburg soils. Soil Sci. Soc. Am. Proc. 1975;39:496-502.
• Mehra O.P., Jackson M.L. Iron oxide removal from soils and clays by a dithionite-citrate system buffered with sodium bicarbonate. Clays Clay Min. 1960;7:317-327.
• Mitchell J.K. Fundamentals of soil behavior, 2nd ed New York: John Wiley and Sons, 1993.
• Rich C.I. Suction apparatus for mounting clay specimens on ceramic tile for x-ray diffraction. Soil Sci. Soc. Am. Proc. 1969;33:815-816.
• Ross G.J. Relationships of specific surface area and clay content to shrink–swell potential of soils having different clay mineralogical compositions. Can. J. Soil Sci. 1978;58:159-166.
• SAS Institute. SAS user's guide: Basics. Cary, NC: SAS Inst, 1985 a Version 5..
• SAS Institute. SAS user's guide: Statistics. Cary, NC: SAS Inst, 1985 b Version 5..
• Soil Survey Staff. Soil survey manual. Washington, DC: U.S. Gov. Print. Office, 1993 USDA-SCS Agric. Handb. 18..
• Soil Survey Staff. Keys to soil taxonomy, 6th ed Blacksburg, VA: Pocahontas Press, 1994.
• Soil Survey Staff. Soil survey laboratory methods manual. Lincoln, NE: National Soil Survey Center, 1996 Ver. 3.0. Soil Survey Invest. Rep. 42..
• Soil Survey Staff. 1997. Map unit interpretation records database. Available at http://www.statlab.iastate.edu/soils/muir/ (verified 22 Nov. 1999).
• Thomas G.W. Exchangeable cations. In: Page A.L., ed. Methods of soil analysis, Part 2, 2nd ed Madison, WI: ASA and SSSA, 1982:159-165 Agron. Monogr. 9..
• Thomas P.J., Baker J.C., Simpson T.W. Variability of the Cecil map unit in Appomattox County, Virginia. Soil Sci. Soc. Am. J. 1989;53:1470-1474.[Abstract/Free Full Text]
• USDA-SCS. Soil survey of Fauquier County, Virginia. Washington, DC: U.S. Gov. Print. Office, 1956.
• Whittig L.D., Allardice W.R. X-ray diffraction techniques. In: Klute A., ed. Methods of soil analysis, Part 1, 2nd ed Madison, WI: ASA and SSSA, 1986:331-362 Agron. Monogr. 9..
• Wilding L.P., Drees L.R. Spatial variability and pedology. In: Wilding L.P., et al. , ed. Pedogenesis and soil taxonomy. I. Concepts and interactions. Amsterdam: Elsevier Sci. Publ. B.V. Elsevier, 1983:83-116.
• Wilding L.P., Jones R.B., Schafer George M. Variation of soil morphological properties within Miami, Celina, and Crosby mapping units in west-central Ohio. Soil Sci. Soc. Am. Proc. 1965;29:711-717.

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