The lowering and control of the head of the water table represents one of the priority issues to the executing company during the phase of preliminary study. A thorough preliminary investigation of the subsoil, aimed at precisely pinpointing the hydrogeological conditions of the area affected by the excavation, is of fundamental importance for the correct dimensioning of drainage systems.
Once the system is dimensioned, the first step at the site is the installation of the intake manifolds. Their placement, according to the needs dictated by the site itself, will have to follow the perimeter of the excavation which limits it. After careful positioning of the intake manifold, the next step is the insertion of the filter tips. This operation, the most sensitive for the success of the drainage of the soil, is done through the use of a specific Jetting motorpump connected with a hose at the end of the lifting tube. The water, sucked by Jetting, is pumped at high pressure from the filtering terminal of the wellpoint tip thus creating a hole in the ground that allows the same tip to penetrate to the depth required.
In clay soils or in those of a compact nature, water pressure alone is not sufficient for drilling the ground and so a special hydraulic drill is used to facilitate driving operations. In the hole thus obtained, the wellpoint is introduced using the Jetting pump and, after abundant washing of the hole drilled, it is connected to the intake manifold. In many cases, however, between the tip of the filter placed at the bottom of the hole and the static level of the groundwater, deformed layers are interposed, impermeable interbeds or clay lenses that hinder the drawing of the water to the filters. Faced with such a situation, after driving the wellpoint with the Jetting pump, the pressure of the pumped water is decreased, saturating the hole to its full height with sand of the proper granularity, keeping the jetting pump in motion until the end of the operation. In so doing, the column of sand created around the wellpoint, puts all the layers of soil above in contact facilitating the drawing of the water towards the filter and preventing clogging.
Once the installation is finished, the next step is the start-up of the . Once the pump has started, the system needs an adjustment aimed at preventing the filter tips from drawing from the ground, together with the water, the air too. The adjustment is made by the in the , it is done by observing the passage of water through the suction hose. A correct adjustment allows the system to have minimum head losses during operation thus reducing the work of the vacuum pump. Once the use of the system is completed, . After turning off the pump, the next step is the and extraction of the . For this operation, you can use any means of lifting, all in a very short time and with extreme ease of execution.