In this article we will present the earth and water pressures options below the excavation for non-continuous wall types, like soldier pile walls, and the related input options within DeepEX software.
A. General Information - Earth and Water Pressures for Different Wall Types
In most deep excavation retaining wall types, the wall section is continuous until the wall tip (concrete diaphragms, secant piles, tangent piles, sheet piles and more), so the earth pressures (active and passive) and the water pressures are fully developed along the whole wall depth.
In case of non-continuous walls (like soldier piles or combined soldier piles - if the sheet pile lagging is not extended to the pile tip), the water and active earth pressures are applied on each embeded pile face. In such cases, we can use the pile diameter (for pipes or borded piles with concrete cover) or the flange width (for driven H beams) for the calculation of such pressures. On the other hand, a larger part of the passive side soil is involved in the development of the passive ressistance. Typically, for the calculation of the passive pressures below the excavation, where the wall is not continuous, we can use as a pressure width 2.5 to 3 times the pile diameter or flange width.
The following figure summarizes the active, passive and water pressures width concept for all wall types (continuous and non-continuous):
B. Wall Width, Spacing and Pressures Widths - Input in DeepEX Software
This paragraph describes the wall section input options in DeepEX software for different wall types.
B1. Horizontal Spacing S
This is the distance taken into consideration in the calculations. It is important, because it is used to divide the calculated moments, shears etc, presenting the results per foot (or per meter) of the wall.
B1.1. Continuous walls (concrete diaphragms - slurry walls , sheet piles): It is recommended to use as spacing 1ft (or 1m).
B1.2. Continuous walls (secant piles): The spacing is the center-to-center distance between the reinforced piles.
B1.3. Continuous walls (tangent piles): The spacing is the center-to-center distance between every pile.
B1.4. Non-Continuous walls (soldier piles - combined sheet piles): The spacing is the center-to-center distance between every pile.
B2. Width D
This parameter is the actual wall width (thickness).
B2.1. Continuous walls (concrete diaphragms - slurry walls): The width is the concrete section thickness (defined by the end user).
B2.2. Continuous walls (Sheet piles): The width is the equivalent wall thickness (defined automatically by the selected steel-section, only graphical).
B2.3. Secant - Tangent piles - Soldier pile wall supported by reinforced concrete piles: The width is the diameter of each pile (defined by the end user).
B2.4. Soldier pile wall supported by steel sections - Combined sheet pile walls:
By default, the steel sections are considered driven, and the Width value is defined as the maximum section dimension of the selected steel beam section (Flange - Web), or the steel pipe diameter.
If we will to use steel sections in drilled holes below the excavation with concrete cover, then we can manually change the width D, to define the hole diameter.
B3. Active and Water width
This is the width for the calculation of the active and water pressures below the excavation where there is no lagging (for soldier pile walls).
B3.1. Continuous walls (diaphragms, sheet piles, secant/tangent piles): It is recommended to use the wall Spacing (as defined above).
B3.2. Non-Continuous walls (soldier piles, combined sheet piles): It is recommended to use the Width value (as defined above).
B4. Passive width
This is the width for the calculation of the passive pressures below the excavation where there is no lagging (for soldier pile walls).
B4.1. Continuous walls (diaphragms, sheet piles, secant/tangent piles): It is recommended to use the wall Spacing (as defined above).
B4.2. Non-Continuous walls (soldier piles, combined sheet piles): It is recommended to use 2.5 to 3 times the Width value (as defined above).
This value (2.5 or 3*D) is limited by the defined Spacing, so if 2.5*D > Spacing, use the Spacing.
C. Combined Sheet Pile Walls
The combined sheet pile walls (king piles) are a combination of steel sections (H piles or pipes), with sheet piles that are used as lagging.
C.1. Default - Continuous Wall
In DeepEX, the sheet piles extend up to the pile tip elevation by default, so the wall is considered to be a continuous wall along the full wall depth.
The pile tip elevation (bottom of the wall) is calculated automatically, since we defile the wall top elevation and the total wall depth.
In that case, we need to specify the wall spacing and thickness as defined above in A.4 and B.4, and then we have to use the Spacing value to all active, passive and water widths).
C.2. Non-Continuous Wall
If we wish to stop the sheet pile sections to a specific elevation, higher than the pile tip elevation, we have to make the following changes:
1. For the active, water and passive widths below the excavation, we have to use the pile width as defined in C.2 and D.2 above.
2. The Custom Elev. Value in the Edit Wall dialog (appears when we double-click on a wall), is the elevation until which the sheet piles are extended. Below this elevation, the active, passive and water widths will be used as defined in (1) right above.
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