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The Wellpoint system is indicated for drainage of the ground-water table. Its low installation cost in comparison with other drainage or freeze well systems
makes it ideal up to a certain depth.
Our company leads its sector and has broad experience in the hire and sale of this type of equipment; we also offer full consultancy services and the installation is carried out by our own technicians. The theory behind the operation of the system is that of installing headers with inlets every 1 or 2 metres at a specific distance from the piece of land that is to be lowered.
These headers are connected to lances by flexible hoses with a filter at the bottom end. This filter varies in thickness depending on the grading of the land. At one of the ends of the headers there is an automatic suction pump with sufficient forced negative pressure for the flow volume required in each installation.
After 2 or 3 days' pumping, the land is dried as desired and can be lowered. The pumps must be working day and night throughout the construction process. If the pumps are stopped when the land has been lowered, the underground water level finds its original level and when the water appears, the physical phenomenon known as siphoning occurs in the lower zones of the land, leading togossible landslides, which could affect the progress of me works.
Different systems are used depending on whether the land is clayey, sandy mud, gravel or sand. The method used to fix the lances depends on the specifications of the land. In clean, fine sand, water at high pressure is used. In hard or clayey land, the lances are fixed in position by mechanical boring.
In clayey land with gravel and irregular permeability, pre-filters must be installed. For the pre-filters, a borehole with sufficient diameter must be made to install the Wellpoint lance and then it is filled with clean, fine sand. This calculation is made by our company‘s technicians. For between-wall constructions, the lances are fixed in the plot of land. when the ground-water table has been consolidated, the lances are replaced by the drainage pipe, which enables later construction work. The distance between the lances depends on the amount of underground water in the area. The lances are connected to a header which, by means of a pump, creates sufficient vacuum to raise the water up through the installation pipes. Once the level of drainage is optimum, the land can be lowered without water. The pumps must be in permanent operation until the construction passes above the ground-water table.
This method enables construction below the ground-water table. The construction of complex screen walls to hold back the water and landslides is not necessary. The difference in constructing these works underground when the land is dry and there are foundations is that the watertightness of the seals is perfect. The proximity of the sea does not prevent the system from functioning perfectly. PSB Group uses the latest generation water-cooled Uniservice Wellpoint pumps.
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