Robert Jansen
Technical Sales Manager
Secant pile wall constructions are used for construction pits in urban areas, temporary sheeting next to existing buildings, and projects where earth retention, water control, and foundation are required in a single structure. On this page, you can read how secant pile walls work, when anchoring is necessary, and why strand anchors are an efficient solution for secant pile wall anchoring.
A secant pile wall is an in-situ formed soil and water-retaining structure consisting of contiguous, intersecting bored piles. The wall is constructed in two phases: first, the primary, unreinforced piles are bored at a distance from each other; then, the secondary, reinforced piles are bored, intersecting the primary piles on both sides. This overlap – typically around 50 mm – creates a closed, contiguous wall.
The secant pile wall is constructed entirely vibration-free and without ground displacement, using a double drilling rig and casing. This makes the technique ideally suited for inner-city projects directly adjacent to existing buildings, foundations, or monuments. Furthermore, the wall can be installed in virtually any soil type, including hard layers and existing masonry, and groundwater lowering is not necessary during construction.
For larger loads and deeper excavations, a secant pile wall is not always capable of independently withstanding the forces that arise. In such cases, an anchored secant pile wall construction is chosen, where an anchoring system transfers the forces to a more stable subsoil. Within these types of constructions, strand anchors play an important role. These offer an efficient and technically strong solution for secant pile wall anchoring, for both temporary and permanent applications.
Other solutions and applications
A secant pile wall is used to safely retain soil and water for building pits, underpinnings, and infrastructural works in urban areas. The wall is formed by drilling and placing interlocking concrete piles in the ground, with the secondary piles fitted with a reinforcing cage or steel profile after concreting to provide the necessary bending strength. Depending on the excavation depth, soil pressure, water pressure, and imposed load from the surroundings, a free-standing secant pile wall may not always be sufficient. In such cases, an anchored secant pile wall is chosen.
Strand anchors are an efficient solution for this, particularly with larger loads and deeper excavations. Compared to other solutions, such as strutting frames or traditional anchor systems, strand anchors offer several advantages:
This makes a secant pile wall solution with strand anchors not only structurally strong but also practically and economically attractive.
When constructing a secant pile wall, several factors determine the structure's functionality:
The choice of the correct execution method has a significant impact on the quality of the wall and the safety of the surroundings.
The construction of a secant pile wall begins with the installation of a concrete guide wall at ground level, into which formwork is placed to define the exact positions of the piles and ensure regular overlap. Subsequently, the primary piles are bored and filled with unreinforced concrete. After partial hardening of the primary piles, the secondary piles are bored, with the cutting head on the casing overlapping the adjacent primary piles on either side. Immediately after concreting the secondary piles, the reinforcement cage or steel section is vibrated into place for the required structural stiffness.
For greater excavation depths, an anchored secant pile wall is almost always used to limit bending moments in the wall and reduce horizontal deformations.An anchored secant pile wall consists of:
In strand anchors, the load is transferred to the wall via the anchor head and the purlin. The anchored part of the anchor then transfers this force to the stable subsoil. When designing and constructing a secant pile wall, it is therefore necessary to consider not only the wall itself, but also:
Every situation is different. In a consultation, we will clearly outline your project and possibilities. You will immediately know where you stand.
Robert Jansen
Technical Sales Manager
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A secant pile wall is an earth and water-retaining structure made up of overlapping bored concrete piles.
The primary, unreinforced piles are bored at intervals; the secondary, reinforced piles cut across the primary piles on both sides, forming a contiguous, closed wall.
Secant pile walls are installed vibration-free and without ground displacement, making them suitable for use directly next to existing buildings and foundations.
Depending on the load and application, a secant pile wall is executed as a free-standing system or as a anchored construction in combination with an anchoring system, such as a strand anchor.
A secant pile wall construction absorbs soil and water pressure via the reinforced secondary piles. The wall is formed by drilling and pouring concrete piles in phases. Thanks to the double drilling rig and casing pipe, no ground relaxation or displacement occurs, allowing work to be carried out directly next to sensitive structures.
For larger loads, the secant pile wall is anchored with a tie-back system. The forces are then transferred via the wall and a waling to the tie-back, which deflects them into a more stable soil layer.
Secant pile walls and tangent pile walls are both constructed from bored concrete piles, but they differ in the way the piles connect to each other:
The choice between the two versions is determined by the waterproofing requirements, ground conditions and the necessary structural capacity of the wall.
An anchored secant pile wall is used when the wall cannot take the resulting loads independently. This is particularly relevant for:
By applying an anchoring system, such as strand anchors, the structure can be designed to be stiffer and more efficient.
Strand anchors are widely used in secant pile wall anchoring due to their high capacity and efficient operation.
Key benefits include:
Additionally, Deepro strand anchors are supplied as a complete system, with all components matched to each other.
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