Introducing E- Quake Drain
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- Created on 22 June 2012
- Written by Dannys
A new method for treating liquefiable soils uses prefabricated vertical drains in conjunction with a reservoir to maintain pore water pressures within the soil at safe levels.
The efficiency of vertical prefabricated wick drains for acceleration of consolidation settlement is well established. This method has virtually replaced the older sand drain method. Wick drains provide a shortened drainage path for dissipation of excess pore water pressures within the soil and provide a clear drainage path to conduct expelled water to the surface. This process is very efficient and cost-effective for acceleration of the consolidation process which takes place over a period of time, often several months.
In an earthquake, efficient drainage is required within seconds. Head losses from water flow within the drain itself become significant. E-QUAKE DRAIN (Patent Pending) makes use of a prefabricated drain with a large cross-sectional area, with flow capacity up to 10,000 times that of the usual wick drain. Head losses within this drain are only a fraction of that in a three-foot diameter stone column with equivalent flow. For further efficiency, a reservoir is provided to accommodate the expelled water without requiring its expulsion to the surface. This reservoir may occur naturally, such as a sand or gravel layer above the water table, or may be installed as an integral part of each drain.
E-QUAKE DRAINS are installed with specialized equipment, capable of penetrating hard intervening layers. The specially-shaped installation mandrel is vibrated during installation as an facilitate penetration, and to densify the liquefiable soil.
These factors combine to provide an extremely cost-effective and efficient system for liquefaction control.
Typical Applications
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- Created on 22 June 2012
- Written by Dannys
Embankment construction
Vertical drains may be used to accelerate settlement of embankments for roadways, railroad tracks, runways, or bridge approaches which must be put into operation very soon after construction is completed. Presettlement can greatly reduce long-term maintenance costs that would result from extended periods of settlement during the life of the project.
Underwater consolidation
Vertical drains may be used to accelerate settlement of soil below water level. The differential pressure created by the surcharge is as effective under water as on land. This technique can be used in preparation for placing tunnel sections in a river bed, for example.
Tank farm foundations & material storage areas
Because of high unit loadings, liquid storage tanks are subject to settlement in soft soils. Vertical drains used in conjunction with a horizontal strip drainage can provide rapid soil consolidation prior to construction. Storage sites for solid materials – coal, ore paper – also can benefit from vertical drainage prior to use.
Landfill Areas
Fill is often placed behind sheet piling walls or cofferdams for use as docks or industrial sites. Vertical drainage is an effective method to accelerate settlement thereby making the site available for use in the shortest possible time.
How Wickdrain Functions
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- Created on 22 June 2012
- Written by Dannys
How WICKDRAIN vertical drain functions
WICKDRAIN prefabricated vertical drain has two components – a core which serves as a water conduit and a geotextile filter fabric which allows water to pass into the core while restricting the movement of soil particles which might clog the core.
The fabric
The WICKDRAIN filter material uses a strong, tough, permeable nonwoven filter fabric of 100% polypropylene specifically designed for drainage. Its continuous filaments are arranged preferentially in the length and width directions of the sheet and thermally bonded. WICKDRAIN filter fabric resists mildew, rotting, insects and chemicals normally encountered in a subsurface drainage system. It is dimensionally stable, wet or dry, has good tear and puncture resistance and will not shrink, grow or unravel.
WICKDRAIN fabric has a unique structure that enhances its function as a filter fabric. It has a large number of openings with a range of opening sizes throughout its structure instead of a few openings of fixed size as in woven fabrics. Its bonded fabrics create a tortuous pathway resembling that of a well graded aggregate filter rather than a simple, straight line exit for soil particles. Because of its unique structure, the filter fabric has both high permeability and the ability to restrict the movement of most soil particles, while allowing the very fine silts to flow into and out of the drain. The initial removal of very fine silts from the soil is beneficial because this leaves the larger particles to form a highly permeable soil network against the fabric. The soil network restricts the further movement of fine soil particles and helps to develop a graded soil filter. This soil filter effectively stops piping of soil and prevents other fine particles from entering the drain. The fabric filter, being more permeable than the soil filter and the natural soil, does not restrict the flow of water into the drain.
The effectiveness of the filter fabric has been proven in government and commercial projects in a wide range of soil types. Its effectiveness has also been confirmed by extensive laboratory tests at the Colorado State University Engineering Research Center. Tests were run with soil mixtures of fine sand, silts and clays which simulated actual systems. Under these conditions, the tests confirmed that, after the initial passage of fine silts through the filter there was:
a)No measurable migration of soil fines within the soil filter or into the drain, and
b)No measurable pressure drop across the filter indicating no reduction of water flow through the fabric. Scanning electron microscopy confirmed that there was no clogging of the fabric.
The core
The WICKDRAIN core is a strong, tough structural member of extruded from 100% polypropylene specifically designed for vertical drain systems. A total of 38 longitudinal grooves distributed on both sides of the core provide discharge passages for water flowing to the surface. The core is dimensionally stable when wet, has good puncture and collapse resistance and will not shrink or rot
Installing Wickdrains
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- Created on 22 June 2012
- Written by Dannys
Installing AMERDRAIN vertical drains
AMERDRAIN vertical drains may be installed employing either vibratory of 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.
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