The total thrust from water retained behind a wall is

P = ½ g_o H²

where H = height of water above bottom of wall, ft (m); and
g_o= unit weight of water, lb/ft³ (62.4 lb/ft³ (1001g/m) for freshwater and 64 lb/ft³ (1026.7 kg/m³) for saltwater)

The thrust is applied at a point H/3 above the bottom of the wall, and the pressure distribution is triangular, with the maximum pressure of 2P / H occurring at the bottom of the wall. Regardless of the slope of the surface behind the wall, the thrust from water is always horizontal.

For walls that retain cohesive soils and are free to move a considerable
amount over a long period of time, the total thrust from the soil (assuming a
level surface) is

P = ½ g H²K_A – 2 c H K_A^1/2

or, because highly cohesive soils generally have small angles of internal
friction,

P = ½ g H²- 2 c H

The thrust is applied at a point somewhat below H /3 from the bottom of the
wall, and the pressure distribution is approximately triangular.

For walls that retain cohesive soils and are free to move only a small amount
or not at all, the total thrust from the soil is

P = ½ g H²K_P

because the cohesion would be lost through plastic flow.

For walls that retain cohesionless soils and are free to move an appreciable amount, the total thrust from the soil is

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LATERAL PRESSURES IN SOILS, FORCES ON RETAINING WALLS

The Rankine theory of lateral earth pressures, used for estimating approximate values for lateral pressures on retaining walls, assumes that the pressure on the back of a vertical wall is the same as the pressure that would exist on a vertical plane in an infinite soil mass. Friction between the wall and the soil is neglected. The pressure on a wall consists of (1) the lateral pressure of the soil held by the wall, (2) the pressure of the water (if any) behind the wall,
and (3) the lateral pressure from any surcharge on the soil behind the wall.

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The soil properties and parameters can be broadly classified as
1)Physical
2)Engineering
3)Index

Physical soil properties include density, particle size and distribution, specific gravity, and water content.
The water content w of a soil sample represents the weight of free water contained in the sample expressed as a percentage of its dry weight.
The degree of saturation S of the sample is the ratio, expressed as percentage, of the volume of free water contained in a sample to its total volume of voids V_v
Porosity n, which is a measure of the relative amount of voids, is the ratio of void volume to the total volume V of soil:

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