This document examines a case history of a pile raft, constructed in Gdansk, Poland. A liquid gas terminal was constructed over 2 rectangular pile caps (71 m x 61.2 m x 0.9 m thick), each one of them supported by 180 reinforced concrete bored piles (diameter: 1 m and 0.62 m, pile depth: 26.5 m).
A model of the pile raft was created with our DeepFND software program. This document presents the software input and calculation results, as well as, a comparison with the measured displacements and estimations of different methods. Some information and data that were not included in the case history, had to be assumed.
![A Pile Raft in Gdansk Poland, Redesigned with DeepFND Software](https://static.wixstatic.com/media/b53ca0_13b5e8e38cfb4f3ea2f7b07e793b5f2c~mv2.jpg/v1/fill/w_147,h_113,al_c,q_80,usm_0.66_1.00_0.01,blur_2,enc_auto/b53ca0_13b5e8e38cfb4f3ea2f7b07e793b5f2c~mv2.jpg)
A. SOIL PROPERTIES AND STRATIGRAPHY
The piles were embedded in sand and alluvium soil layers. The following Table summarizes the estimated soil properties for all soil types.
Table 1: Soil Properties and Soil Layers (Stratigraphy)
Soil Layer Top Elev. (m) | Soil (-) | Soil Type (-) | Friction Angle (deg) | Cohesion (c’ or Su) (kPa) | Total Unit Weight (KN/m3) | Young’s Modulus (kPa) | Poisson’s Ratio (-) | |
5 | 1 | Sand (Fill) | 30 | 0 | 18 | 32000 | 0.35 | |
2.9 | 2 | Silty Sand | 26 | 2.4 | 16 | 52000 | 0.45 | |
-2.5 | 3 | Soft Sand | 28 | 0 | 17 | 9000 | 0.35 | |
-7 | 4 | Medium Sand | 34 | 0 | 18 | 35000 | 0.35 | |
-9.7 and -18 | 5 | Medium Silt | 28 | 14.5 | 19.6 | 32000 | 0.45 | |
-11.9 And -23.6 | 6 | Dense Clay (Undrained) | - | 15 | 15 | 1300 | 0.45 | |
-24 | 7 | Sandy Clay (Undrained) | - | 150 | 20 | 36000 | 0.32 | |
B. PILE SECTION PROPERTIES AND PILE POSITIONS (LAYOUT)
In the original project, two types of piles where used:
- 1 m diameter reinforced concrete piles, distributed on the whole pile raft
- 0.62 m diameter reinforced concrete piles, used along the 3 raft sides
C: GENERATED MODEL - RESULT GRAPHS (DEEPFND)
![A Pile Raft in Gdansk Poland, Redesigned with DeepFND Software](https://static.wixstatic.com/media/b53ca0_670b8208d15849e690408fb6043f4607~mv2.png/v1/fill/w_80,h_20,al_c,q_85,usm_0.66_1.00_0.01,blur_2,enc_auto/b53ca0_670b8208d15849e690408fb6043f4607~mv2.png)
![A Pile Raft in Gdansk Poland, Redesigned with DeepFND Software](https://static.wixstatic.com/media/b53ca0_954eb45b1e1a4eb98149279739a6b21d~mv2.jpg/v1/fill/w_147,h_101,al_c,q_80,usm_0.66_1.00_0.01,blur_2,enc_auto/b53ca0_954eb45b1e1a4eb98149279739a6b21d~mv2.jpg)
D: DEEPFND PILE RAFT SETTLEMENTS VS MEASURED AND PREDICTED WITH OTHER METHODS
Pile raft settlements were measured during the project construction. DeepFND software predicted a maximum of 17 mm settlements at the last pile row location (closest to the pile raft edge), matching the measured settlement values. Table 2 below, presents the predicted settlements at the middle of the pile raft, in comparison to values predicted from other methods and sources.
Table 2: Maximum Settlement Predictions with DeepFND and Other Methods
Method | Settlement (mm) |
DeepFND – Pile Rafts Module (Non-Linear Soil Springs Method) | 33 |
Equivalent Foundation According to Polish Code (PN-69) | 32.7 |
Equivalent Foundation According to Tomlinson | 30.9 |
Equivalent Foundation According to Poulos (Randolph Formula) | 34 |
Equivalent Foundation According to Van Impe | 33.4 |
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