The Chicken Claw Foundation System for Buildings

In the field of civil engineering, the foundation is one of the most crucial structural components of any building. It serves as the base that transfers the load of the entire structure to the ground, ensuring stability, strength, and safety. Among various types of foundation systems, the cakar ayam or “chicken claw” foundation stands out as an innovative Indonesian invention that combines modern engineering with practical local wisdom. The chicken claw foundation system was developed to provide stability on soft or weak soils that are commonly found in many parts of Indonesia and other tropical countries. This article explores the concept, structure, working principles, advantages, and applications of the cakar ayam foundation system in modern building construction.

History and Concept

The cakar ayam foundation was invented by Professor Dr. Ir. Sedijatmo in the early 1960s in Indonesia. Initially, it was developed to support electric transmission towers built on swampy and unstable ground. The soft soil conditions made it difficult for conventional deep foundations or pile systems to maintain stability. Sedijatmo’s innovation provided a breakthrough: a system that distributes loads evenly through a combination of concrete slabs and vertical cylindrical pipes that act like “chicken claws” penetrating into the soil.

The term “cakar ayam,” which means “chicken claw” in Indonesian, was inspired by the way a chicken’s claw grips the ground firmly for balance. Similarly, this foundation system grips the soil and resists settlement or tilting, even on soft and saturated land.

Structure of the Cakar Ayam Foundation

The cakar ayam foundation consists of three main components:

1. Reinforced Concrete Slab (Plate):
   This is a thick horizontal concrete plate, typically ranging from 10 to 15 centimeters thick. It acts as the main load-bearing surface that distributes the building load across a large area of soil.

2. Concrete Pipes (Cylinders):
   Beneath the slab are vertical reinforced concrete pipes, usually diameters of 1 to 1.2 meters and lengths of 1.5 to 3 meters, depending on soil conditions and load requirements. These pipes are cast monolithically with the slab, meaning they are built together as one continuous structure.

3. Soil Interaction Zone:
   The pipes extend downward into the soil and create a composite system where the slab and pipes work together. The pipes resist both vertical and lateral loads, while the slab provides overall rigidity and distributes stresses evenly.

The configuration resembles a chicken’s claw gripping the earth, hence the name. The number and spacing of pipes depend on the type of soil, load capacity, and structural design requirements.

Working Principle

The cakar ayam foundation works by integrating the slab and pipes into a single, rigid structure that interacts effectively with the ground. When a building load is applied, it spreads through the concrete plate and is transmitted to the vertical pipes. The pipes increase the contact area with the soil and provide resistance to settlement. Additionally, the hollow pipes can be left open or filled with compacted soil, depending on the engineering design.

This system minimizes differential settlement, which is a common problem in soft soil areas. The rigid plate maintains the level of the structure, while the pipes act as anchors, improving stability against shear and lateral forces. The synergy between these two components results in a foundation that behaves like a floating raft with deep claws.

Advantages of the Cakar Ayam Foundation

The cakar ayam system offers several notable benefits, making it suitable for various engineering applications:

1. Excellent Stability on Soft Soils
   This foundation performs exceptionally well on weak or compressible soils such as clay, peat, or swampy ground. It prevents excessive settlement and maintains even load distribution.

2. No Need for Deep Piles
   Unlike conventional pile foundations that require deep drilling and heavy equipment, the cakar ayam system can be constructed with simpler methods and shallower excavation, saving time and cost.

3. Uniform Settlement Control
   Because the slab and pipes work as a unified system, the risk of differential settlement between different parts of the building is minimized.

4. Increased Bearing Capacity
   The vertical pipes act as friction and end-bearing elements, enhancing the foundation’s overall load-bearing capacity.

5. Resistance to Earthquakes and Vibration
   The rigid monolithic structure provides excellent resistance against seismic loads, making it ideal for earthquake-prone regions like Indonesia.

6. Adaptability
   It can be used for various structures, including buildings, bridges, airport runways, towers, and industrial facilities.

7. Low Maintenance
   Once constructed, the system requires little to no maintenance over its lifespan.

Disadvantages and Limitations

Despite its advantages, the cakar ayam foundation system also has some limitations that need to be considered:

1. High Initial Construction Cost
   Although it may reduce costs in soft soil treatment, the use of reinforced concrete and large quantities of material can make initial costs higher.

2. Complex Formwork and Casting Process
   Casting the pipes monolithically with the slab requires precise engineering and skilled labor.

3. Not Suitable for All Soil Types
   The system is most effective on soft or semi-soft soils. In dense sandy or rocky soils, conventional pile foundations may be more efficient.

4. Limited Depth Penetration
   The pipes typically extend only a few meters into the soil. For very deep weak layers, other deep foundation systems may be required.

Applications in Modern Construction

The cakar ayam foundation has been widely applied in Indonesia and other countries, particularly for infrastructure built on problematic soil. Some of its most notable applications include:

• Airport Runways: The system was used in the construction of Soekarno-Hatta International Airport in Jakarta, providing stability on soft ground.

• Transmission Towers: Originally developed for high-voltage transmission towers across swampy areas.

• Industrial Buildings and Warehouses: Provides a solid base for heavy machinery on weak soils.

• Bridges and Highways: Used for structures requiring large load distribution and minimal settlement.

• Residential and Commercial Buildings: Particularly useful in coastal or delta regions with low bearing capacity.

This foundation system continues to inspire engineers to design efficient and environmentally adaptable foundations for challenging soil conditions.

Innovation and Development

Over time, engineers have improved and adapted the cakar ayam concept with modern technologies. New variations include hybrid systems that combine chicken claw foundations with geotextile reinforcements, gravel piles, or soil stabilization materials to further increase bearing capacity and durability. Computer simulations and finite element analysis (FEA) are now used to optimize the design and performance of this foundation system.

Conclusion

The cakar ayam or chicken claw foundation system is a remarkable example of engineering innovation originating from Indonesia. It reflects the creativity of Professor Sedijatmo in addressing real-world challenges with a practical and efficient design. By combining a reinforced concrete slab with vertical pipes that penetrate the soil like claws, this system achieves exceptional stability even on weak or saturated ground.

In today’s era of rapid urbanization and infrastructure development, the cakar ayam foundation remains highly relevant. It offers engineers a sustainable, cost-effective, and technically sound solution for building on difficult soil conditions. More importantly, it stands as a proud symbol of Indonesian ingenuity contributing to global civil engineering.