The building foundations was composed by 3 different types of piles: Bored piles, CFA and CSP (cased CFA). The bored piles were excavated using GEO’s G3 System, for soil stabilization.
The Polymud soil stabilization fluid was selected for this particular project for its advantages in terms of versatility, with minimum requirements for equipment and treatment, and simplicity of management in a reduced capacity batching plant. GEO collaborated very closely with JRL, from the preparation of the operations and throughout the project. There was an exclusive and dedicated support to the client on site.
Challenges
Variable soil conditions, with changing thickness of granular soil layers (Scour Feature) and the management of the bored piles sequence, required a capable stabilization fluid. Potential fluid loss was anticipated, related with the very deep water table level and the extend of the very porous granular soil layers.
Enormous space restrictions, constraining the size of the slurry batching plant, and ease to manage the needed slurry volumes. Impossibility to use a full casing solution, because it would difficult the operations and have a greater impact in the already slim production.
Project located in a dense urban area, where removal of the excavated soil was very scrutinized
Solution
GEO’s integrated solution, of products and services, was highly valued. The technical support was essential in the preparation and mobilization of equipment, as per the existing restrictions, and assured products usage optimization while implementing the best procedures.
The tailoring of the batching plant setup, and an optimized management of the fluid volume made possible the completion of piles with a volumetric capacity higher than the existing plant storage capacity, without wasting products, assuring production cycles and the stabilization of the excavation successfully. Final pile quality was confirmed and verified by means of TIP testing.
This project was executed using Polymud slurry, having the pH adjustment done with Sodium Hydroxide. The other product used was GFiber and it was applied in very specific piles, having more permeable soil where fluid loss was expected. Slurry maintained its quality, remaining clean throughout the various cycles, with minimal redosing. All excavated soil had minimum traces of slurry, remaining very dry, and could easily be moved out of site
Key Figures
Scope:
A total of 66 piles were executed: 15 having Ø1500mm, 35 of Ø1180mm and 16 with Ø950mm. Reaching a maximum depth of 37 meters.
Achievements:
Slurry loss to soil formation was controlled with the usage of Gfiber. Production targets as per client expectation: one Ø1500mm pile/day and two Ø900mm piles/day, using a single drilling rig. Final cost for slurry products was under the initial estimation even after scope increase.
Geology:
Top (debris) soil layer, with crushed bricks and rubble, from 0 to 10; layer of fine to medium silty Sand, with fine to coarse gravel, from 10 to 13m; followed by sandy Gravel, from 13 to 21.5m (the depth of this layer was variable depending on the scour effect), then a firm to very stiff (London) Clay, from 21.5 to 33m; followed by very dense cemented fine Sand, from 33m to 40m.
