Discover why soil testing is essential for safe and durable construction in Bali. Learn about core samples, penetration tests, and laboratory analysis to ensure your building’s foundation is rock solid.

Building a dream structure in Bali requires more than just an eye-catching design; it demands a deep understanding of the ground beneath your feet. Before a single brick is laid, investigating the soil is paramount to guarantee the longevity and safety of your construction. In today’s fast-paced construction environment, where standard designs are often re-used, understanding the specific conditions of your building site is more important than ever.

Why Soil Testing Matters

• Foundation Integrity: The foundation is the most critical component of any building, bearing the entire weight of the structure. It must be designed to match the building’s load and the strength of the ground supporting it. Standard foundation designs may be adequate for light, single-story buildings, but they often fail to account for the additional weight of multiple stories, high ceilings, and heavy roofing materials.
• Preventing Cracks and Instability: A large number of buildings in Bali experience cracking due to poorly designed foundations. This is a direct consequence of not properly investigating the ground’s load-bearing capacity. Some ground types, such as soft clays, may not be able to handle the weight, leading to instability.
• Understanding Soil Composition: Soil tests reveal the different layers of earth beneath the surface, including the type of soil, its composition, and its ability to resist pressure and movement. This information is crucial for designing foundations that can withstand the specific challenges of each site.

The Three Pillars of Soil Testing

In Bali, three main types of tests are generally performed to thoroughly investigate the ground before construction:

1. Core Samples: Boreholes are drilled at strategic locations to extract cylindrical soil samples. These samples are then analyzed in a laboratory to determine the soil type at different depths.
2. Penetration Tests: A steel rod with a cone-shaped end is pushed into the ground, and the force required to push it is measured. This test assesses the ground’s ability to support the weight of the building.
3. Laboratory Tests: The collected core samples are subjected to a battery of tests to analyze the strength and composition of the soil. These tests identify whether the soil is loose, firm, or subject to liquefaction under pressure or movement.

Real-World Example: Learning from Past Mistakes

Consider a case study from a former rice field, where the ground was found to be particularly problematic. Soil tests revealed:

• The top 2 meters: Soft, weak clay.
• 2-4 meters: Firmer, but still unsuitable for heavy loads.
• 4+ meters: A layer of rock (sandstone) with a much higher weight-bearing capacity.

This particular case demonstrated that standard 1.5-meter deep foundations were not suitable for the site. In fact, increasing the depth to 4 meters would increase the load-bearing capacity tenfold.

Beware of Site Filling Practices

It is common practice to fill former rice fields with a layer of light coral stone before building. While it may seem to provide a solid surface, this practice can actually make the foundation problems worse, as the coral stone layer sits on top of weak clay, increasing the risk of sinking or movement. The weight of the building must be transferred to firm ground via the foundations, not just resting on the surface.

Special Considerations

• Thixotropic Clays: Some clays may become more fluid under stress, which can lead to landslides. Soil testing can identify such risky clays.
• Earthquake Conditions: Certain types of gravel or sand are susceptible to liquefaction during earthquakes, where the ground temporarily behaves like a liquid, and buildings can collapse. Soil tests can assess the risk of liquefaction.
• Water Absorption: The wet and dry cycles in Bali can cause the clay to expand and contract, leading to cracks in buildings. Proper foundations are crucial to avoid this problem.

Conclusion

Understanding the soil properties before construction is a fundamental step for ensuring structural integrity and preventing costly damage. Investing in thorough soil testing is a crucial step to construct stable, durable, and safe structures.