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The modern world of geotechnical engineering is characterized by dynamic progress, both in terms of the materials used and the technologies supporting design work. This is not without reason since we all know that necessity is the mother of invention. Such progress is mainly driven by the fact that there are fewer and fewer places in our surroundings with easy hydrogeological conditions for the design of foundations and other structures that may be considered "geotechnical".

The number of challenges facing geotechnical engineers in their daily work is constantly growing, and these are not only technical problems, but also those arising from time pressure and budget constraints. Fortunately, modern geotechnical engineers have access to up-to-date knowledge and skills, and they can use modern tools in their work, including specialized programs for performing simple but also more complex geotechnical analyses.

One such program used by our geotechnical team at the Pietrucha Group in their daily work, related to the design of vinyl sheeting structures, is the Sheeting Check module which is part of the GEO-5 software, provided by Fine Software.

The GEO-5 Sheeting Check

In the past, geotechnical engineers used to rely mainly on their experience and intuition to assess the soil stability to design foundations and other structures. They also used manual calculation methods, which could be time-consuming and prone to errors.

However, the complexity of modern engineering projects requires the use of more advanced tools. In this context, the GEO-5 software comprising the Sheeting Check module, is the key tool that allows for accurate modelling and performance analysis of vinyl sheet pile structures under various conditions.

One of the most useful functionalities of the Sheeting Check is method of elasto-plastic non-linear analysis where the pressure on the construction is determined by its deformation, which allows for very accurate simulations. Such aspect is especially important in the case of vinyl sheet piles because in comparison with i.e. steel sheet piles, profiles made of PVC are much more flexible, which results in higher probability of displacement and, as a result, the shift of the soil mass around the structure.

In addition, the program takes into account many standards, inter alia EN 1997 or American standards, allowing for the application of appropriate safety factors and different calculation approaches and scenarios, depending on the location of the project. This ensures that the designs comply with current safety requirements and standards anywhere in the world.

How to implement vinyl sheet piles in a given geotechnical project?

A major advantage of the Sheeting Check highly intuitive module is the speed in which the structure models are created.

When designing a structure using vinyl sheet piles, the first step is to correctly model the situation related to the soil layers, i.e. their type and thickness. To complete this step, the design engineer may use the geotechnical documentation of the project or the soil database incorporated in the software.

Next, one must go to the Geometry tab and edit the default reinforced concrete wall by choosing the VINYL SHEET PILE WALL from the wall type menu. In the next step, the designer then selects the specific vinyl sheet pile from the profile CATALOGUE where it is possible to select the EcoLock or SuperLock sheet piles manufactured by the Pietrucha Group.

For example, one may select GW-610/9 profile and specify its length and then move on to the next steps in the project modelling i.e. the depth and shape of excavation, the shape of backfill, the ground water level, pressure etc.

At this point, there is an important aspect of vinyl sheet piles to consider when using them in projects where they are to work as a retaining structure. It is necessary to keep in mind that PVC, from which vinyl sheet piles are made, is a polymer material and, like in the case of all polymers, certain external factors may affect its properties over time. Such factors include constant pressure (active pressure) in time resulting in the creep effect, temperature and atmospheric conditions.

The Pietrucha approach

It is important to emphasize here that, based on our vast experience, the Pietrucha Group has developed an individual approach to the design of EcoLock and SuperLock sheet piles, depending on the project assumptions. As a result, we are able to estimate with great accuracy the impact of the above factors on the technical parameters of the material after, for example, 50 years. As a result, vinyl sheet pile structures designed using the Pietrucha approach will be much safer.

This brings us to another advantage of the Sheeting Check module. In the MATERIAL tab, one may define specific material parameters such as: tensile strength, Young Modulus and Shear modulus, which will correspond to the conditions after x years since the construction.

The target factor of safety used in the software is FS=2, which provides adequate safety for most designs. However, based on our practice, we believe that sometimes FS=2 is too low and sometimes too conservative.

In the coming weeks, we will be providing more insight into our design approach and its practical implementation, so stay tuned!

Once the modelling stage is complete, one may have a look at the calculation results made on the basis of our design model. When it comes to vinyl sheet piles, it is essential to consider the predicted maximum construction displacement. Due to a considerably lower Young Modulus of PVC, the stiffness parameter of vinyl sheet piles is lower, which may result in significant deformation. One may, for example, come across a situation where the bending moment and the shearing force generated within the structure are 20% only and at the same time, the displacement is well exceeding 50 mm. 

In such situation, where our earlier GW-610/9 profile does not fulfil its purpose, it is always worth checking stronger profiles, dedicated to construct retaining walls, e.g. GW-580, GW-458 or even the SuperLock hybrid sheet pile.

It is also worth mentioning that using the Sheeting Check module one may analyse the behavior of the structure during individual construction phases or in different and variable conditions affecting the structure (e.g. variable water level). This requires adding a construction phase above the model view and accordingly adjust the situations for this phase.

Once all construction phases have been analysed and the construction is safe, one may move to generating the final report which may also include 2D and 3D images of the structure, model assumptions and calculations. Such report constitutes an excellent attachment to the design documentation and also a proof that the design engineer did the job with due care when modelling structures in which vinyl sheet piles are used. What is more, the investor may double-check whether the design assumptions implemented correspond with the reality.

Summary

The progress of geotechnical technologies and materials requires equally corresponding development of design tools. Fortunately, it is happening and geotechnical designers have many tools at their disposal to make quick analyses used for initial verification of the adopted technology.

One of such tools is the Sheeting Check module available with the GEO-5 software package. The tool not only simplifies and expedited the design process, but also significantly increases the accuracy and safety of projects using vinyl and hybrid sheet piles such as EcoLock and SuperLock.

As a result, geotechnicians may predict the behavior of structures with greater certainty and precision, which is invaluable in the face of the complex challenges of contemporary civil engineering.

Remember that our project support team offers free assistance in selecting the right profile for your project and that you may consult with our engineers any queries that may arise.

If you already have this program and would like to use vinyl sheet piles in your next project, but you are not sure how to do it, you are welcome to contact the engineers from The Pietrucha Group.