Abstract #

This document examines the design of diaphragm walls in deep excavations, comparing the traditional Polish Code PN-83/B-03010 with the newly introduced Eurocode 7. It presents a detailed analysis of three standard design cases: a cantilever diaphragm wall, an anchored diaphragm wall, and a strutted diaphragm wall. Calculations were performed using both the dependent pressures method and Finite Element Method (FEM), providing insights into the differences between these approaches and their implications for the design of safe and efficient retaining structures.

Technical Relevance #

This document is highly relevant for geotechnical engineers and designers involved in deep excavation projects. With the adoption of Eurocode 7, understanding the differences between traditional and new design approaches is crucial. This paper provides a comprehensive comparison of methods, highlighting key considerations that will affect the design and safety of diaphragm walls in various geotechnical conditions.

Target Audience #

The document is intended for geotechnical engineers, researchers, and professionals who are involved in the design and analysis of retaining structures, particularly those transitioning from local standards to Eurocode 7. It is also relevant for students and academics studying the practical application of Eurocode 7 in geotechnical engineering.

Software and Methodology #

The calculations were performed using both traditional methods and modern FEM-based software. The dependent pressures method was applied using GEO5 Sheeting Check software, while FEM analysis was conducted using PLAXIS. The study considered three design approaches (DA1A, DA1B, and DA2) specified in Eurocode 7, with each approach involving different combinations of partial safety factors. The methodology involved modeling the soil-structure interaction, groundwater conditions, and the impact of construction stages on the stability of the diaphragm walls.

Process Description #

The document begins with an overview of the calculation assumptions and the selection of soil parameters. Three design cases are then analyzed: 1) a cantilever diaphragm wall in sandy soil, 2) an anchored diaphragm wall, and 3) a strutted diaphragm wall. For each case, the document details the geometry, soil properties, and loads considered in the analysis. The results from the dependent pressures method and FEM analysis are compared to evaluate the embedment depth, bending moments, and lateral displacements of the walls.

Main Findings #

The study found that Eurocode 7’s DA1B approach, which applies more stringent partial safety factors, generally predicts greater wall embedment depths, higher bending moments, and larger horizontal displacements compared to the Polish Code. Significant differences were also observed between the results of the dependent pressures method and FEM analysis, with FEM typically predicting smaller lateral displacements. The choice of modulus of elasticity in FEM analysis was identified as a critical factor influencing the results.

Practical Applications #

The findings are directly applicable to the design of diaphragm walls in deep excavation projects, particularly in regions transitioning to Eurocode 7. Engineers can use these insights to select the appropriate design approach and calculation method, ensuring that the retaining structures are both safe and cost-effective. The study also highlights the importance of careful parameter selection in FEM analysis to avoid underestimating wall displacements.

Limitations and Considerations #

The document notes that while the design cases considered are relatively simple, the insights gained are still valuable for more complex scenarios. However, the results are highly dependent on the accuracy of input parameters, particularly in FEM analysis. Engineers should be cautious when selecting soil stiffness values and should consider conducting sensitivity analyses to account for uncertainties in the design.

Conclusions #

The paper concludes that for the design of diaphragm walls in deep excavations, Eurocode 7’s DA2 approach offers an economical solution that provides a comparable level of safety to the traditional Polish Code. However, the use of FEM for calculating lateral displacements requires special attention to the modulus of elasticity, as overestimation can lead to unsafe design outcomes. The study emphasizes the need for careful consideration of design approach and calculation method when applying Eurocode 7 in practice.

Related Resources #

Further reading includes case studies on the application of Eurocode 7 in other geotechnical structures, as well as guidelines on the calibration of FEM models for accurate prediction of soil-structure interaction. Additional resources on the use of dependent pressures methods in different soil conditions can provide deeper insights into optimizing diaphragm wall designs.

📥 Download LINK