Case studies

Częstochowa: pvc piling used to reinforce flood walls

This publication presents a case study involving the use of the EcoLock vinyl sheet piling structure designed and manufactured by the Pietrucha Group in the project of reconstruction and modernisation of flood protection structures in the area of Częstochowa, which began in 2015.

Due to its subsurface and groundwater conditions, the region of Częstochowa is an area at risk of floods. For example, in 2010 and during the so-called Millennium Flood in 1997, all three rivers flowing through the city: Warta, Kucelinka and Stradomka flooded. Among other things, 36 kilometres of roads and several bridges in Częstochowa were damaged. Losses were estimated at PLN 13 million. In Częstochowa Poviat, more than 2,000 residential buildings and 1,520 farm buildings were flooded. Water caused damage to 17 roads and 2 bridges. It was then that attention was drawn to the need for reconstruction and modernisation of the almost century-old flood protection structures in the region. The modernisation works as part of this multi-stage project started in 2015.

Challenge:

In the area of Częstochowa, the Warta separates into two streams, the left stream – the main river stream with its tributary, the Stradomka, and the right stream – the Kucelinka channel with a length of 6.87 km. Most of the flood walls in the area were built in the 1920s and 1930s from local material. Currently, they do not fulfil their flood protection function due to physical degradation resulting from repeated cycles of soaking, drying and freezing of the body of the wall. Walls are subject to biological degradation as a result of decomposing of root systems of dying plants and related root decay processes as well as colonisation by species of animals using walls as a procreation and residence site. The bilateral embankments of the Warta belong to importance class IV, according to Polish classification; however, following new guidelines, they should be classified in class II and III. The investment of the flood wall modernisation was divided into several stages, as the total length of embankments to be strengthened is about 19 kilometres. This publication concerns a section with a length of 1.7 km.

Subsurface and groundwater conditions:

The analysis of the geological conditions confirmed that the walls are made of different kinds of sand and covered with a layer of humus. The substrate under the walls includes mainly fine or medium sand. Dynamic probing conducted revealed that both the wall and the substrate have a low or medium density. The groundwater table is at a depth of about 3.2-4.2 m from the crowning of the wall.

Actions taken:

To ensure an adequate level of flood protection, the strengthening of the walls involved work such as: grubbing-up of trees and shrubs, removing the humus layer, compaction of the existing walls, supplementing and compaction of soil in order to achieve the desired height of the wall crowning, increasing tightness using vinyl sheet piling with the GW-460/5.5 profile by Pietrucha, construction of a vinyl cap above the sheet piling and construction of an emergency road with a width of 2 m on the crowning of the wall. A typical project cross section through the crowning of the wall is shown in the figure below.

The length of vinyl sheet piles was selected so as to improve tightness of the wall but not to prevent the flow of groundwater from external areas towards its natural outlet, the Warta river. It was therefore assumed that groundwater will flow under the structure. In the event of heavy rainfall, this solution will ensure a quick drying of agricultural land and residential areas located east of the river. It is worth noting that the driving of the sheet pile increases the stability of the flood walls due to an additional compaction of soil in areas surrounding the sheet pile. Sheet piling made of Pietrucha sheet piles will also provide additional protection in case of a local landslide (scouring) of the waterside slope of the wall, because it will act as a retaining structure keeping the remaining body of the wall. It will also provide uniform tightness conditions regardless of the type of soil of the body and the subsoil under the body of the wall. Construction work was carried out according to the guidelines of the project. In the described stage, 3,700 sheet piles were installed and the daily progress ranged between 30 and 40 m.

Conclusions:

The sample project described proved that the EcoLock vinyl sheet pile system by Pietrucha is an effective alternative to common methods for modernising flood walls. Structures made of the Pietrucha vinyl sheet piles are resistant to corrosion, and their efficient installation can shorten the duration of the investment. Thanks to a low weight of sheet piles, already at the stage of transportation investment costs are reduced. The cost of 1 m2 of the PVC sheet pile used in this project together with its installation is several times lower than the cost of a steel sheet pile that could be an alternative in this project. Total savings resulting from the technology of vinyl sheet piles used compared to steel sheet piling amounted to approximately PLN 3 million. Water engineering is still facing new challenges, and Pietrucha delivers solutions tailored to the needs of new realities resulting from the rapidly changing climatic conditions worldwide.

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