Pressure from Weight of Soil

Pressure from weight of soil, abbreviated as \(p_s\), also called soil pressure or earth pressure, refers to the force exerted by the mass of soil on a retaining wall, foundation, top of pipe, or any structure in contact with the soil.  This pressure is primarily influenced by the weight of the soil above and behind the structure.  The pressure exerted by the weight of soil depends on several factors, including the type of soil, its density, and the depth of the soil.  The pressure generally increases with depth due to the increasing weight of the soil above.

There are different types of soil pressure that can be encountered, depending on the conditions and the structural configuration.

Soil Pressure that can be Encountered

Active Pressure  -  This refers to the lateral pressure exerted by the soil on a retaining wall or a structure.  It tends to push the wall or structure away.
Passive Pressure  -  This is the opposite of active pressure and refers to the resistance offered by the soil against the movement of a retaining wall or structure.  Passive pressure tends to push the wall or structure towards the soil.
At-Rest Pressure  -  This type of soil pressure assumes that the soil is in a state of equilibrium and exerts a lateral pressure that is neither pushing nor resisting movement.  At-rest pressure is often used in simplified soil mechanics analyses.

Calculating the exact pressure from the weight of soil on a structure can be complex and involves considering various factors such as soil properties, the geometry of the structure, and the boundary conditions.  Engineers and geotechnical specialists use different methods, such as soil mechanics principles, numerical modeling, and empirical formulas, to estimate and analyze soil pressures for design purposes.  It is important to account for the pressure from the weight of soil when designing foundations, retaining walls, and other structures to ensure their stability and structural integrity.

Pressure from Weight of Soil Formula
\( p_s \;=\;  \gamma_s \cdot h  \)     (Pressure from Weight of Soil) \( \gamma_s \;=\;  \dfrac{ p_s }{ h }\)  \( h \;=\;  \dfrac{ p_s }{  \gamma_s }\)
Symbol	English	Metric
\( p_s \) = pressure from weight of soil	\(lbf\;/\;in^2\)	\(Pa\)
\( \gamma_s \)  (Greek symbol gamma) = solid unit weight	\(lbm\;/\;ft^3\)	\(N\;/\;m^3\)
\( h \) = height from pipe top to ground surface	\(in\)	\(mm\)