As the most important industrial location in Baden-Württemberg with around 125,000 registered inhabitants, Heilbronn is going through a phase of dynamic urban development and the trend of growth is set to continue. Consequently, the demand for apartments is rising and all new housing development areas must be connected to the existing infrastructure.
The company Walter Bohr- und Injektionstechnik from Albruck, Germany is a Putzmeister customer specialising in different shotcrete techniques and recently backed the city of Heilbronn in its proposal to connect a new residential area to the existing sewage network. Microtunneling was the only method that was worth entertaining to lay the 950 metre connecting sewer to the existing system because of the restricted conditions in the built-up inner city. Microtunneling is a method of jacking pipes underground, whereby open shafts only needs to be excavated at the points where the pipe starts and finishes.
Safety is paramount
The start and target pits required in Heilbronn were each 8 metres in diameter and extended to a depth of 9 metres. The company Walter constructed a shotcrete wall using a Putzmeister P 715 to stabilise the earth inside the shafts. Equipped with the company's own chemical control, the powerful, mobile, compact piston pump had no trouble in conveying the required material with a 8 mm grain size along the 40 metre long hose and into the shafts. The roadworthy T-chassis, low weight and remarkably compact dimensions of the P 715 made sure that the machine was easy to transport to the construction site and manoeuvre into position alongside the two shafts. Specially designed for construction sites, the state-of-the-art piston pump also operates reliably when used continuously.
Dry spraying method versus wet spraying method
Previously, shafts of this kind were usually stabilised using dry spraying techniques, whereby the cement and the aggregate is mixed together dry and conveyed along a pipe or hose to the mixing nozzle in a jet of air. Water is added to the dry mixture at the nozzle to ensure the mix achieves the required consistence. However, adding an insufficient quantity of water immediately results in excessive dust formation, which is why most companies have switched to the wet spraying method. Although slightly more expensive, it is less strenuous for the operators and also offers a more consistent quality with good compression and adhesion characteristics. This is the reason why wet spraying equipment was used to construct the start and target pits for the Heilbronn wastewater project.
The company Walter Bohr- und Injektionstechnik from Albruck, Germany is a Putzmeister customer specialising in different shotcrete techniques and recently backed the city of Heilbronn in its proposal to connect a new residential area to the existing sewage network. Microtunneling was the only method that was worth entertaining to lay the 950 metre connecting sewer to the existing system because of the restricted conditions in the built-up inner city. Microtunneling is a method of jacking pipes underground, whereby open shafts only needs to be excavated at the points where the pipe starts and finishes.
Safety is paramount
The start and target pits required in Heilbronn were each 8 metres in diameter and extended to a depth of 9 metres. The company Walter constructed a shotcrete wall using a Putzmeister P 715 to stabilise the earth inside the shafts. Equipped with the company's own chemical control, the powerful, mobile, compact piston pump had no trouble in conveying the required material with a 8 mm grain size along the 40 metre long hose and into the shafts. The roadworthy T-chassis, low weight and remarkably compact dimensions of the P 715 made sure that the machine was easy to transport to the construction site and manoeuvre into position alongside the two shafts. Specially designed for construction sites, the state-of-the-art piston pump also operates reliably when used continuously.
Dry spraying method versus wet spraying method
Previously, shafts of this kind were usually stabilised using dry spraying techniques, whereby the cement and the aggregate is mixed together dry and conveyed along a pipe or hose to the mixing nozzle in a jet of air. Water is added to the dry mixture at the nozzle to ensure the mix achieves the required consistence. However, adding an insufficient quantity of water immediately results in excessive dust formation, which is why most companies have switched to the wet spraying method. Although slightly more expensive, it is less strenuous for the operators and also offers a more consistent quality with good compression and adhesion characteristics. This is the reason why wet spraying equipment was used to construct the start and target pits for the Heilbronn wastewater project.
