Shrinkage Limit

Shrinkage limit, abbreviated as SL, a dimensionless number, is a property of soil in geotechnical engineering that represents the water content at which further drying of the soil does not cause any noticeable reduction in volume of soil.  It is an important parameter used to characterize the behavior of soils during drying and wetting processes.  Other words it goes from semi-solid to a solid state.

The shrinkage limit is one of the Atterberg limits, a set of standardized tests used to classify fine grained soils based on their plasticity and behavior under different moisture conditions.

The shrinkage limit is typically determined through laboratory testing using the shrinkage dish method.  In this test, a soil sample is initially saturated and then allowed to air dry in a shallow dish.  The water content at which the soil volume remains constant is defined as the shrinkage limit.  The shrinkage limit is influenced by various factors, including the mineral composition of the soil, its structure, and the presence of organic matter.  It's used in conjunction with other Atterberg limits, such as the liquid limit and plastic limit, to classify soils into various categories such as clay, silt, and clayey silt.

The shrinkage limit is used in geotechnical engineering to assess the potential for soil volume changes due to fluctuations in moisture content.  It's relevant in applications such as foundation design, slope stability analysis, and construction planning, where understanding the behavior of soil under different moisture conditions is crucial.

• See Article  -  Atterberg Limits

 

Shrinkage limit formula
\( SL \;=\;  \left(m_1 - m_2\right)  - \left(V_1 - V_2\right)  \; PL  \;/\; m_2 \)
Symbol	English	Metric
\( SL \) = Shrinkage Limit	\(dimensionless\)	\(dimensionless\)
\( m_1 \)  = Inlet Wet Mass of Soil	\(lbm\)	\(kg\)
\( m_2 \)  = Final Dry Mass of Soil	\(lbm\)	\(kg\)
\( V_1 \)  = Inlet Volume of Soil	\(ft^3\)	\(m^3\)
\( V_2 \)  = Final Volume of Dry Soil	\(ft^3\)	\(m^3\)
\( PL \)  =  Plastic Limit	\(dimensionless\)	\(dimensionless\)