BeauDrain - Vacuum Consolidation System
From Vacuum Consolidation
Vacuum consolidation was first introduced in 1952 by W. Kjellman, the inventor of the pre-fabricated vertical drain. Since then, vacuum consolidation has been in frequent use in constructions with a high risk for instability. The BeauDrain technique was developed at the beginning of this century as an alternative to the traditional vacuum technique.
The BeauDrain technique
In the BeauDrain technique, a horizontal drain is connected to vertical drains and used to apply a pressure reduction (vacuum) to the vertical drains. Through the application of a pressure reduction to the drains, the use of additional surcharge of sand can be dispensed with, thereby saving time.
Why BeauDrain vacuum consolidation?
In the preparation of a site for construction, the developer often opts for the use of normal vertical drainage with additional surcharge. In most cases this is the best and cheapest solution. This is certainly the case if sufficient time, space and sand are available during the course of the project. If, for whatever reason, a project has to be delivered or an embankment has to be created very quickly, it can be the case that no space is available for additional surcharge or the application of extra sand is too expensive, Cofra’s settlement accelerating technique BeauDrain is the solution. The use of the BeauDrain technique with a vacuum of 50 kPa and an embankment of 2 metres exhibits the same settlement behaviour as vertical drainage installed with the same drain spacing and an embankment of 2 m + 50 kPa = 4.5 m sand. This means that when BeauDrain is used, including the application of the aforementioned 2 metres of sand, the settlement occurs more quickly. This also has advantages for stability as the subsoil adapts to a higher load than is actually present. As a result, the first fill layers, in particular, can be considerably thicker and embankment creation can take place more quickly.
Installation of the BeauDrain System
The installation machine uses a specially designed coulter to pull a horizontal collecting drain to a maximum depth of 2.5 m beneath the installation level (depending upon the thickness of the woring platform, the course and the groundwater level). As part of the production process, this horizontal drain is automatically connected to the top of a vertical drain installed in the same work operation. Finally, a strip of membrane is installed on top of the horizontal drain to improve the sealing between the atmosphere and the drainage barrier. After the installation of a pre-determined number of drains, a blind section of the drain is led to the surface where this is connected to a vacuum pump.
- Faster preparation of residential areas
- Installation of infrastructure (roads, railways and airports)
- Installation of dikes
- Faster installation of embankments
- Preparation of sites where surcharge material is expensive or scarce
- Short installation period and clean work site after installation
- No soil is excavated, thus preventing any damage as a result of horizontal deformation of the soil due to relaxation and insufficient filling
- No supply of drainage sand or removal/storage of removed soil
- A lagre working depth is achievable thanks to the use of vertical drains
- Sand layers can be followed at a safe distance
- The use of vacuum pressure gives rise to an increase in effective pressure; this reduces the risks of instability in the case of ongoing embankment creation
- The existing body of soil is used as a sealing medium, thereby dispensing with the need for a surface membrane
- The work site becomes available for other activities immediately after
- installation and remains so
- The barrier configurations can be adapted to the soil type to be consolidated
- Horizontal deformation in the event of ongoing embankment creation is considerably reduced
- The BeauDrain system also allows for a considerable reduction of secular settlements and settlement differences.