Reduce soil settlement times from years to months
Soil consolidation using prefabricated vertical drains (also commonly called wick drains or band drains) can reduce settlement times from years to months. Most settlement can occur during construction, thus keeping post-construction settlements to a minimum.
Consolidation of water-saturated, fine-grained soil occurs very slowly because the low permeability of these soils impedes the escape of pore water from the soil voids. Even under large temporary surcharge loads, settlements can take years because of this slow water movement and the great distance the water must move to exit the soil.
The installation of prefabricated vertical drains greatly reduces the distance the water must move to reach a free drainage path, and therefore greatly increases settlement rate. Drain spacing may be adjusted to match the required settlement time.
AMERDRAIN-W prefabricated wick drains are installed vertically to depths exceeding 200 feet (65 meters). The water, under pressure in excess of hydrostatic, flows through the filter fabric of the drain and into the channels of the drain core where it can flow vertically out of the soil. This flow may be either up or down to intersecting natural sand layers or to the surface where a sand drainage blanket or prefabricated strip drains are provided.
The water in the soil has only to travel the distance to the nearest drain to reach a free drainage path. The drains are usually placed in a triangular configuration of 3 to 12 feet (1 to 4 meters) – depending on the desired consolidation time. As a result of this method of accelerating the consolidation process, uneven post-construction settlements can be virtually eliminated.
AMERDRAIN-W vertical drains may be installed employing either vibratory or static crowd methods. In either case, the drain is enclosed in a tubular steel mandrel of small cross-sectional area (usually 2 x 5 inches). A small steel anchor plate is attached to the wick at the bottom of the mandrel. The mandrel is then driven into the soil either with a static crowd or vibratory rig. When the design depth is reached, the mandrel is extracted. The anchor plate retains the drain in the soil. When the mandrel is fully extracted, the drain is cut off, a new anchor plate is installed and the process begins again.