The screw piles were first used by Alexander Mitchell in the 1830s to install lighthouses in the shifting sands of England. The first lighthouse on screw piles was the Maplin Sands lighthouse on the Thames. The piles at that time were made of cast iron and had a diameter of 5 inches with a helix of 1.2 meters in diameter.
In his patent, Alexander Mitchell described two properties of the helix:
- It enters the ground by driving the pile, making it easier to screw in the pile than to drive it.
- It takes up some of the load, increasing the bearing capacity of the pile.
In 1848, Mitchell gave a detailed report on the Maplin Sands project. Forty people, employed by the Trinity House company, worked on a raft of 100 square meters. Using long poles, they turned the pile until it entered the ground. When the pile reached a screwing depth of 27 feet (about 8 meters), a platform was mounted on top, which held 12 people. The total weight was over a tonne, and there was no significant movement of the pile.
The use of screw piles in maritime areas led to strong growth in places that had been abandoned for years. Piled wharves were built for commercial or pleasure ports in the United States, Africa, and India.
The ocean docks
With the success that Mitchell had with his lighthouses, he expanded the use of his invention to other construction sites. In 1847, he undertook the construction of a quay 12 miles south of Arklow, Ireland. In his report, he indicated that at the beginning, he encountered tremendous difficulties: despite the solidity of the barges and rafts used on other construction sites for piles, the unprotected sea sent waves of such magnitude that the use of this technique became impossible. Therefore, the technique used consisted of starting from the shore by putting the piles, and, in sections of 17 feet, driving them into the sea.
Mitchell’s success with his lighthouses led him to expand the use of his invention to other construction sites. In 1847, he began building the quay 12 miles south of Arklow, Ireland. In his report, he indicated that he initially encountered tremendous difficulties. Despite the solidity of the barges and rafts used on other sites for piles, the unprotected open sea sent waves of such magnitude that the use of this technique became impossible. The technique used, therefore, consisted of starting from the shore, driving the piles, and, in sections of 17 feet, entering the sea.
This construction method proved to be very easy and economical. The piles were driven into the ground using a 32-foot-diameter capstan, which rotated with a ribbon. Mitchell described the soil and piles as follows: “The bottom was composed of sand and gravel to a depth of 8 feet, then the layer of hard clay began. For this reason, 5-inch piles with 2-foot-diameter helices driven into the ground to a depth of 11 to 15 feet were sufficient.”
A team of about ten men could complete a 17-foot span in one day, despite difficult weather conditions. The installation method chosen was a very secure method for the time.
At the same time, Mitchell registered a company that he called The Screw Pile Company. In fact, this construction site demonstrated a new use for piles: quays and bridges. This caused a sharp increase in activity around the piles, thanks to one of the builders of the Wexford quay – Eugenius Birch.
In 1862, Johnson, who was Mitchell’s agent in India, described the construction of the mooring quay in Madras, India. The 1080-foot-long by 40-foot-wide quay was begun in 1859. Johnson wrote: “When it is learned that there have been several attempts to build a quay in Madras, one understands that the matter has been very dangerous… At the end of construction, there was no vibration of the quay under the effect of the swell, which demonstrates the advantage of screw piles over any other system.”
Below is an engraving of the Madras quay that appeared in the London News in 1862.
Among the most well-known engineers practicing screw piles, we must mention Eugenius Birch, a member of ICE. He probably started his work with Mitchell, and in 1847 he learned about the expiration of the 7-year patent on screw piles, which allowed him to build without paying royalties to Mitchell. His first project was the Margate Jetty dock.
The end of Mitchell’s patent gave great freedom to many engineers who wanted to use screw piles. Birch built many docks, including those in Hastings and Birbank, which can still be seen today. We can see that the construction scheme of the docks is very similar, with vertical piles. Data on the piles is incomplete. We only know that the piles used had a helix diameter between 90 and 120 cm, and their pitch was between 6 and 8 inches.
The durability of these quays was considerable: some are still in use today. The majority were destroyed in the 1950s, and the cause of destruction was either fire in one of the pavilions on the quays or a boat colliding with the structure.
Propeller-driven cylinders: an alternative technology
Many wharves were built on screw piles in ports around the world. They were designed for loading and unloading cargo or for passengers boarding ships.
In the United States, engineers designed cast iron cylinder-shaped piles with a smaller diameter helix compared to the pile. The maximum thickness of the pile was 2.5 inches and decreased to 3/10 of an inch at the edge of the helix.
The most remarkable structure of the time was the Woolrich dock, which was used to load military equipment onto royal navy ships. At the end of the dock, an 80-ton crane was supported by five 5-inch screw piles and a central 7-inch pile with a propeller diameter of 9 feet and 6 inches. All the piles were installed using a capstan similar to Mitchell’s.
Note that cylindrical piles could be used with a central wooden shaft, which was common in the 19th century. By the early 20th century, steel became much more accessible.
At the time, the strongest competitor to screw piles was the Jetted Disc Pile, which was a variant of the screw pile where the propeller was hollow and had openings. A pump circulated water through the propeller via the central shaft, which, by suction, caused the pile to descend. When pumping stopped, the soil descended onto the propeller, ensuring anchorage. Several installations of this kind were made, but the technique was evidently too expensive to compete with screw piles.
Development of modern times piles
The first house on screw piles was built in Boston in 1900.
At the beginning of the 20th century, the screw pile technique was replaced by driven piles for the following reasons: concrete became a more economical material than the metal of the time, labor costs decreased due to numerous crises at the beginning of the century, and, above all, the pile hammer was invented and became widespread.
For 80 years, the technique was only used by the military and had its second youth only in the 1980s. This period is characterized by powerful and compact hydraulic installations that appear on the market. This trend reduces the cost of installing foundations on screw piles compared to other types of foundations and makes this technique advantageous when considering the cost of labor in developed countries.
The British school versus the Soviet school
En URSS, explorant et exploitant ses immenses territoires après la Deuxième Guerre Mondiale, la technique des pieux vissés est devenue la plus répandue dans beaucoup de régions, surtout celles avec du permafrost. Les avantages de la technique ont été démontrés par prof. Vladislav Dmokhovski.
Historiquement il est arrivé que dans les années 50-60 du XX siècle en URSS ont été développés les bases théoriques d’utilisation des pieux vissés, la technologie d’exécution des travaux, et ont été conçues les installations pour la mise en place des pieux. Un apport immense dans la technologie a été fait par G. Shapiro, N. Bibina, E. Kriukov et al. Dans leurs travaux sont données des critères de choix de la géométrie et des caractéristiques techniques des pieux, ainsi que les recommandations sur les matériaux. Des expérimentations à large échelle ont donné des informations sur l’utilisation des pieux dans les sols divers, ce qui a permis de développer la méthode optimale de mise en place des pieux. La première norme sur les pieux vissés date de 1955. Vers les années 1961-64 il y a eu la première norme sur l’utilisation des pieux vissés comme fondations pour des pylones des lignes à très haute tension de hauteur jusqu’à 245 mètres.
L’utilisation intensive des pieux vissés dans l’énergétique date des années 60 du XX siècle. Ceci est du au boom de construction dans les villes, et l’augmentation de la quantité des travaux de montage lors de la construction des ouvrages de télécommunication.
En URSS le développement des pieux vissés se passait indépendamment des travaux des scientifiques occidentaux, et les objectifs prioritaires de ce développement était la vitesse et la simplicité de pose dans les sols à haute densité. Le pieux qui répondait au mieux à ces objectifs était celui développé par Prof. Viktor Zhelezkov.
Les développeurs occidentaux, au contraire, ont mis un accent sur le fait d’assurer la portance maximale du pieu en diminuant la quantité des matériaux utilisés. Ceci a mené à la configuration où l’hélice est soudée directement à l’arbre du pieu, et reprend une partie de charge. Afin d’augmenter la capacité portante, le nombre de tours de l’hélice et son diamètre ont été augmentés.
In the USSR, exploring and exploiting its vast territories after World War II, the technique of screw piles became the most widespread in many regions, especially those with permafrost. The advantages of the technique were demonstrated by Prof. Vladislav Dmokhovski.
Historically, in the 1950s-60s in the USSR, the theoretical basis for the use of screw piles, the technology for carrying out the work, and the installations for installing the piles were developed. Immense contributions to the technology were made by G. Shapiro, N. Bibina, E. Kriukov, and others. Their work provided criteria for choosing the geometry and technical characteristics of the piles, as well as recommendations on materials. Large-scale experiments provided information on the use of piles in various soils, which allowed for the development of the optimal method for installing the piles. The first standard for screw piles dates back to 1955. In the years 1961-64, there was the first standard for the use of screw piles as foundations for pylons for high-voltage power lines up to 245 meters in height.
The intensive use of screw piles in the energy sector dates back to the 1960s. This is due to the construction boom in cities and the increase in the amount of installation work during the construction of telecommunication facilities.
In the USSR, the development of screw piles proceeded independently of the work of Western scientists, and the priority objectives of this development were speed and simplicity of installation in high-density soils. The pile that best met these objectives was developed by Prof. Viktor Zhelezkov.
Western developers, on the contrary, emphasized ensuring the maximum bearing capacity of the pile by reducing the amount of materials used. This led to the configuration where the helix is directly welded to the shaft of the pile and carries a part of the load. To increase the bearing capacity, the number of turns of the helix and its diameter were increased.
Today – French screwed piles
The only historic structure built on screw piles currently exists in France. It is the Walde lighthouse, built in Marck plage (Calais) in 1857 by Alexandre Mitchell’s teams. It was put into service in 1859, and in the 1950s it was equipped with gas. In 1957, a propane explosion destroyed the superstructure, located 11 meters above the ground, and since then the ruins of the lighthouse have been deteriorating. In 1986, the lighthouse was completely abandoned as it had no utility. The diameter of the platform is 7 meters, and the piles are driven 5 meters deep by a team of 40 people. One pile was completed per day, and the work for the 7 piles took about 2 weeks. Converting to current money, each worker was paid about 850 British pounds for the work, and the estimated cost of the project was 150,000€. The piles were manufactured in London, at the Blackfriars, by Messrs. Rennie’s works factory, which was located on Holland Street and no longer exists.
Screw piles have taken 11% of the global foundation market, and this percentage is constantly increasing.
Despite this, in France, it is considered that screw piles are the prerogative of only certain industrial buildings, while screw piles developed by AEDIFICANTES make screw pile foundations the most economical and effective, thanks to their adaptation to French soils. Specific calculations have made it possible to design an optimal solution for France: different from existing methods, it combines ease of installation with controlled bearing capacity.