In the world of deep foundation and earth-retention systems, two widely recognized and essential techniques are contiguous piling and Bohrpfähle. These methods are often utilized in urban developments, infrastructure projects, and large-scale excavations, offering effective solutions for ground support, stability, and load transfer in challenging geotechnical environments. Their application is particularly prominent in areas where space constraints, soil conditions, or structural load requirements demand precision-engineered solutions.

Contiguous piling is a retaining wall system created by placing concrete piles adjacent to each other with small gaps left between them. These piles are constructed using bored or driven methods and are designed to provide lateral support to excavations or slopes. The small spacing between the piles allows some groundwater flow, which can be beneficial in certain soil types where managing hydrostatic pressure is essential. However, the wall can be made watertight by combining this system with grouting or shotcrete to seal the gaps when water ingress needs to be controlled. Contiguous piled walls are typically used in basements, underground car parks, tunnels, and shafts where retaining earth pressure is critical during and after construction.]

The strength of contiguous piling lies in its adaptability. It can be adjusted to varying soil types and site conditions, including soft clays, loose sands, and gravels. The construction sequence involves augering or boring the holes, inserting reinforcement cages, and then concreting. The piles may be reinforced fully or partially, depending on the structural requirements. During excavation, temporary ground anchors or struts are often installed to reduce deflection and increase stability.

Bohrpfähle, a German term meaning “bored piles,” is another widely used deep foundation method that supports heavy structural loads and ensures stability in problematic soil strata. Bohrpfähle are formed by drilling cylindrical holes into the ground, placing reinforcement cages, and filling the void with concrete. They differ from driven piles in that they cause minimal vibration and noise, making them ideal for urban or sensitive environments where disturbances must be kept to a minimum.

One of the significant advantages of Bohrpfähle is their load-bearing capacity. These piles can be constructed to great depths and diameters, accommodating the structural demands of high-rise buildings, bridges, and industrial facilities. They can be used singly or in groups, depending on the load distribution and foundation design. When arranged in rows or clusters, they can also serve as retaining structures or form the backbone of secant or tangent pile walls.

While both contiguous piling and Bohrpfähle offer specific benefits, their combination often results in highly efficient foundation and retaining systems. For example, in the construction of deep basements or underground transit stations, Bohrpfähle can be employed to form contiguous pile walls, blending the advantages of both methods—load-bearing capacity and excavation support. Furthermore, advancements in rotary drilling rigs and concrete pumping systems have improved the speed and accuracy of installation, reducing project timelines and increasing safety on-site.

Environmental and geotechnical considerations also influence the selection of these methods. In groundwater-sensitive zones, the gaps in contiguous piling may need additional treatment to prevent water seepage. Similarly, in areas with high lateral pressure or unstable soils, Bohrpfähle may require special casing or support fluids during drilling to maintain bore stability and prevent collapse.

As construction projects become more complex and urban development intensifies, the demand for reliable and flexible ground engineering solutions like contiguous piling and Bohrpfähle continues to grow. These technologies not only provide practical solutions for supporting structures but also play a vital role in enhancing safety, sustainability, and efficiency in modern construction practices.