A. Introduction - Project Description - Model in DeepEX
Occasionally we get a chance to compare measured deep excavation performance against different methods. This 21.2m deep excavation case history in Santiago, Chile compares various conventional methods against measured ground anchor loads.
The excavation was constructed in competent cohesive gravels and was supported by two levels of ground anchors and 0.8m diameter reinforced concrete piles spaced at 3.2m. Reported displacements were under 2.0 cm. A 2m pile embedment below the final excavation subgrade was provided.
Image: Model in DeepEX, last construction stage
B. Analysis Options - Results - Support Reactions Comparison
Various popular methods of conventional analysis were examined. In all cases wall to soil interface friction was ignored.
Most conventional methods produced reasonable agreement and came within 10% of the maximum measured loads. The PECK methods with the tributary height approach underpredicted reactions by as much as 25%. The CALTRANS approach with FHWA pressures overpredicted the upper ground anchor load by 17% and underpredicted the lower ground anchor load by 20%. The method producing the closest match was the German EAB approach which came in remarkably close. The approach of using 50% of active and 50% of at-rest earth pressures severely overpredicted support reactions vs. the actual measured loads.
Table: Theoretical vs. Measured Ground Anchor Reactions
Image: Soil Pressures and Support Reactions - FHWA Pressures Method
A critical aspect in case histories like this is the actual applied ground anchor prestress. In this project, the applied prestresses were in closer agreement to the German EAB approach. Should prestress levels had been applied in consistency with CALTRANS loads, measured ground anchor reactions could have been different. With all due respect to German engineering, this case history clearly demonstrates the importance of evaluating different deep excavation analysis methods.
DeepEX is the ultimate software program for design and analysis of Deep Excavations! Design any wall type and support system in the most efficient way!
Download now a FREE 30 days trial version and check all software capabilities! Create any deep excavation model in minutes!
Get a Free online presentation! Learn about all software features and capabilities!
Get the most powerful shoring design software! Customize your version!
Review our software programs for geotechnical engineers and contractors!
All software features and capabilities! Review all available design methods and analysis standards!
We continue our research and we introduce new unique features that extend the software capabilities!
Export and visualize 3D deep excavation models in Virtual and Augmented Reality! Impress your clients!