Improving Soil For Construction Using A Wick Drain

By Author: William Hauselberg
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When layers of silt and clay accumulate over time, they make a very poor foundation for solid construction. A good method for soil improvement is the use of a wick drain. If left to compact itself, the loose layers of build-up will gradually compress themselves over the course of ten to twenty years. With the help of this device, that process is condensed to just a few months, saving you construction time, effort, and money.

What is it exactly?

A wick drain usually consists of an inner plastic core with narrow canals that act as channels for water to flow up. This core is encased in a geosynthetic jacket that allows water to permeate the filter and reach the canals. They’re wide and thin, often measuring four inches wide and 1/8 inches thick.

How does a wick drain work?

The reason compaction takes such a long time is that there is a lot of water remaining in the soil. Adding to the problem, as the water is far below the surface, removing it is a challenge. These drains are driven deep into the soil till they reach the compression layer, up to 200 feet below the surface, and are anchored with a metal ...
... plate to hold them in place. Many drains must be placed is fairly close proximity of each other in order for the drainage system to effectively help the area shed its water. Once the wick drain is in place, pore water begins to move laterally toward the drain and then follows the canals’ path up and out of the ground. After landing on the surface, the water enters the drainage layer and funnels off. After the water is removed from the lower layers, soft soil is able to settle much more rapidly.

Consolidation of the ground itself depends on its own capacity to be compressed. However, drain spacing, fill height, and consolidation time can aid the process of compaction to produce an optimal result.

What projects use this method for soil improvement?

Virtually anything that requires construction on solid ground that moves as little as possible can make use of this technique, given that the project is to take place on land with high water content in its deeper layers. Projects can include: dams, storage areas and warehouses, airport runways, housing complexes, shopping centers, parking lots, bridge abutments, developed roads and freeways, schools, hospitals, stadiums, office buildings, hotels, skyscrapers, factories, etc.

The author has an immense knowledge on wick drain. Know more about soil improvement related info in his website http://www.geo-solutions.com/tech-papers/biopolymer-trench-drain.php and http://www.geo-solutions.com/construction-technologies/ground-improvement.php