- Wellpointing Dewatering
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- Wellpoint Systems
Wellpoint Dewatering systems enable the lowering of the groundwater table, which allows safe excavation below the normal water table. This method has been used for many years for a wide range of applications from small excavations through to major construction projects. Khansaheb Sykes have been providing wellpoint dewatering solutions in the Middle East for over 35 years. This method of dewatering is easy to install, cost effective and reliable.
The principle of Wellpointing is simple. Individual small wells, called Wellpoints, which are generally 40 to 50mm in diameter and either 6 or 7 metres in length, are inserted into the soil using either a drill or high pressure water, this depends on the ground conditions. The wellpoints are installed around the proposed excavations and connected via a suction header pipe to a surface mounted centrifugal pump, this unit has a built in high capacity vacuum pump, which evacuates the suction pipework automatically priming the pump. Pumping from the Wellpoint installation allows lowering of the ground water within the area adjacent to, or enclosed by, the installation and excavation can take place in safe workable conditions.
Wellpoint Dewatering is one of the most economical, flexible and stable methods of dewatering available. Our site investigations and calculations together with our knowledge of previous subsoil conditions, enables us to recommend and install the appropriate equipment. Once the system is up and running we continue to support the project with our 24/7 service either on site or via our local depots.
You may have the best-run site but, without efficient groundwater control, you can soon get bogged down in costly and uncomfortable problems, with serious implications for the project and for Health and Safety. That’s where we come in.
Our ground water reduction capabilities have been tried-and-tested many times in the harsh climatic and our adopted wellpoint dewatering pumps are well adapted for the saline water conditions found in this region.
We provide a complete groundwater control service: from site investigation design and calculations, using our knowledge of previous subsoil conditions, to recommending and installing appropriate ground water dewatering system. Typically, we install a number of wellpoint tubes 40mm to 60mm in diameter, protected by a gravel filter screen, so collecting underground water effectively.
All our wellpointing dewatering pumps are fitted as standard with high capacity vacuum pumps, enabling the maximum drawdown and greatest number of wellpoints to be installed. Dewatering Pumps deployed include the Univac WP150/60 the GP150/60 both are high efficiency, fully automatic general-purpose unit, these dewatering pumps come in either diesel or electric.
Depending on the type of excavation and project requirement, different methods of wellpoint dewatering systems can be used. All of these systems are based on the same principle of using multiple wellpoints joined into a common header pipe, but the type of installations is varied to meet the demands of the project.
Wellpoint Dewatering Closed Ring Installation
Where bulk excavation is required, the most frequently employed method of Wellpoint dewatering involves the enclosure of the excavation area by a ring of header pipe with Wellpoints placed at predetermined intervals. Excavations to a depth of 5m can be effectively dewatered by a single ring of Wellpoints. Where the water table is to be lowered to a deeper level, a multiple-stage Wellpoint system is employed. Following achievement of the initial drawdown, the ground is excavated to the limits of the first stage and a second installation is set at this new level. It is possible to introduce a number of further stages in this manner, although in the case of very deep excavations, the possibility of adopting a combination of drainage systems should be considered.
Wellpoint Dewatering Progressive Line Installation
Designed for pipelines and other similar applications, a progressive or roll along dewatering approach is installed alongside the route, preceding excavation and pipe laying. Equipment from a previously completed and backfilled section is installed at the head of the line, removing the need for large quantities of equipment.
Where deeper excavation is required close to other buildings or in restricted areas a buried system can be considered. With this method the header pipe is buried below the ground level which in turn allows the wellpoints to be installed at greater depth and thereby provide dewatering to lower levels.
Open dewatering systems enable one to lower groundwater table adequately in cohesive and low permeable soils. Water is pumped off directly from sumps (ditches) along the toes of the slopes of the excavation works. The suction hose with strainer is merely placed in the sump and the collected water is primed and discharged. This makes the open dewatering system easy to install and simple to operate. The open dewatering system utilizes self priming or vacuum assisted centrifugal pumps; the Sykes GP range of pumps are ideally suited for this application.
Wellpointing is an economical and flexible method of stabilising water-bearing soils during excavation. By temporarily lowering the water surface to below the greatest excavation depth soil stability of the sides and bottom is assured.
Depending on the soil conditions, support systems are often not required allowing rapid progression of work. Dewatering by wellpoints is by no means confined to conditions of soil instability. It is widely used wherever water levels need to be lowered prior to excavations. Although there is a physical limitation on the depth to which one system can lower the water table, a multistage system installed in stages can lower the groundwater to much greater depths.