Circular foundations

PNL presents the alternative to traditional concrete foundations in the infrastructure sector: the Krinner screw foundations. A circular technique based on the thousands of years old and proven principle of pile foundations. An interview with Emiel Pijnenburg, already the third generation of family business PNL, about the many advantages of this circular foundation technique.

Krinner Schraubfundamente is considered the inventor of the screw foundation, according to Pijnenburg. "Already in 1994, well before the topic of sustainability played a role, founder Klaus Krinner presented a sustainable and environmentally friendly alternative to traditional concrete foundations with the screw foundation. The principle has remained unchanged in all these years and now enjoys worldwide fame. Since 2008, we have continued to specialize in this field and have official representation of Krinner's products for the Netherlands."

Directly taxable

The screw foundation consists of a galvanized steel tube with welded-on threads, designed to absorb horizontal and vertical loads in the ground. "The tube is twisted into the ground with special machines and acquires bearing capacity even in this way," explains Pijnenburg. "The possible load absorption is in no way inferior to that of a concrete foundation. Indeed, a screw foundation only offers advantages. No earth moving is required, fast assembly is guaranteed and the foundation can be loaded immediately. At the end of its service life, the screw foundation can also be easily dismantled and used elsewhere. There is no question of permanent soil damage; the soil recovers to its natural state." 

Economic alternative

Screw foundations can be used both as top-layer foundations and as depth foundations. Pijnenburg: "Whether for structures on slopes, narrow and difficult to access construction sites or temporary construction projects, thanks to the many variants, Krinner screw foundations offer an economical answer in almost any situation. In locations where the load-bearing soil structure is at a considerable depth, safe and stable depth foundations can be realized quickly and economically with extendable V Series screw foundations. The V Series is statistically fully calculated and can be spliced up to a maximum of 18 meters. By the way, the basic material of the Krinner screw foundations is largely recycled European steel that is galvanized 100 um inside and outside."

Infra and rail infrastructure

Pijnenburg sees plenty of opportunities for Krinner screw foundations in Dutch infrastructure. "They are already widely used abroad, for example as foundations for traffic lights, traffic signs along highways, noise barriers, light masts, (smaller) bridges and jetties. Nuisance is kept to a minimum, because the foundation is immediately loadable. The potential is enormous." The Krinner system is also already being used for supporting bicycle paths to prevent subsidence, as it is worldwide in rail infrastructure. "In America, Canada and Germany, permission has been granted by the local 'ProRail' to found noise barriers along the railroad tracks on Krinner screw foundations. Again, the speed of assembly, immediate load capacity and minimal inconvenience are decisive factors in this."

Foundation plan and assembly sequence

Based on the loads to be absorbed by the foundation, the correct diameter screw foundations are determined by PNL. Krinner has a wide range of screw foundations in many different diameters. The length depends on the type of foundation, which requires a sounding. "Based on these factors, we make an appropriate recommendation and draw up a foundation plan. To test and confirm the assumptions from the foundation plan in practice, a load test is performed. This also determines the assembly parameters, such as the minimum torque. After approval of the load test, we proceed to assembly. The positions of the screw foundations are plotted, after which we screw them in using an electric or hydraulic machine. During the screw-in process, the screw-in torque is measured and recorded. Afterwards, we hand over the report with all the data to the client."

Krinner screw foundations are the foundation for the future, Pijnenburg summarizes. "They are durable, innovative, particularly environmentally friendly and ultimately cost-saving. Initially, our product may be more expensive, but the fast assembly process and immediate load-bearing capacity ultimately reduce costs." PNL has representation in several regions in the Netherlands, enabling it to quickly and efficiently supply "the whole of the Netherlands" with circular foundations. "Via the CO2 calculator on our website, we immediately make the CO2 savings transparent, which can be as much as 80%!"