Engineering properties of marls.
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2015-04-01
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Abstract:The term “marl” is used to designate soft, carbonate‐rich, fine‐grained soils, which pose concerns related to both settlement and
stability. Despite the prevalence of marls in Indiana and the concerns associated with their behavior, very limited work has been done to
study the engineering properties of these soils. This was the motivation for this research project, which involved two primary activities:
a) the creation of a map and database of existing information on marl deposits in Indiana; and b) an in‐depth characterization of the
properties of a marl deposit in Daviess County, which was considered representative of similar deposits encountered in Indiana.
The marl database was generated using ArcGIS 10.0.from information available at the INDOT, and involved mining data from over
five thousand boreholes.
The second part of the project involved field tests (seismic cone penetration tests, standard penetration tests, field vane shear
tests), and laboratory experiments (index tests, incremental and constant rate of strain consolidation tests, and K0‐consolidated
undrained triaxial tests) conducted on high quality Shelby tubes samples. Additionally, the mineralogy and the microstructure of the soil
were studied in detail.
The laboratory tests reveal that the deposit was not homogeneous as was initially anticipated, but was, instead, formed by two
types of soils that repeat in horizontal thin layers. These two soils, referred to as ‘soil M’ and ‘soil C’, are both characterized by very high
calcium carbonate contents but show distinct index and engineering properties, that may be ascribed to differences in mineralogy and
composition. This stratification is not detected by the field tests.
The consolidation tests show that the deposit has an OCR less than 2 and compressibility parameters markedly dependent on
stress level, as typical of sensitive soils. K0‐consolidated undrained compression triaxial tests show that both soils exhibit normalized
behavior, and that the relationship between strength and stress history is well described by the SHANSEP equation (although the
SHANSEP parameters differ for the two soils).
Comparison of the field data and laboratory results provides the means to validate published correlations for interpretation of the
geotechnical properties of marls from field results. For the site examined, correlations to estimate shear wave velocity, stress history,
and undrained strength from CPT results are identified. Implementation recommendations are provided for soil identification, sampling
and specimen preparation, interpretation of filed data, and preliminary design.
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