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Common mistakes when working with backfill

Experience shows that most foundation problems on fill soils arise from common mistakes that can be easily avoided with the right approach.

Common mistakes developers make

•        Forgoing engineering surveys to save money is the most common and costly mistake. Without soil data, it's impossible to accurately calculate pile length and their bearing capacity.

•        Using short piles that don't reach dense soil is the second most common mistake. Developers choose standard 2.5-3 meter piles without considering the thickness of the backfill. As a result, the piles rest on soft soil and settle.

•        Installing piles immediately after backfilling, without allowing time for settling, causes the fresh backfill to compact under the piles, causing them to settle. The minimum curing period for backfill is 3-6 months with good compaction.

•        Ignoring high groundwater levels, water liquefies the soil and reduces its bearing capacity. Without drainage and waterproofing, the backfill turns into mush, especially in the spring when the snow melts.

•        No capping or grillage—each pile operates independently, resulting in uneven settlement. Rigid capping connects all piles into a single system and compensates for localized subsidence.

How to avoid mistakes

Follow a simple algorithm to minimize risks:

1. Order engineering and geological surveys before design begins.

2. Apply backfill with high-quality soil and compact it layer by layer.

3. Allow the backfill to cure for at least 3–6 months before installing piles.

4. Calculate pile lengths with a margin to ensure they reach the load-bearing layer.

5. Control the torque when installing each pile.

6. Be sure to install a grillage or pile field bracing.

7. Provide drainage and a blind area to protect against water.

Don't trust the "experience" of installers who say, "We always install two-meter piles here, and everything is fine." Every site is unique, and what worked for your neighbor may not work for you. Only engineering surveys will provide accurate information.

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