VIBRATION-FREE SOIL DISPLACEMENT CAST-IN-PLACE CONCRETE PILE
The Fundex pile is a true full section cast in place reinforced concrete pile, installed by torque and down pressure, completely free of vibration and with no piledriving noise. It is a true soil displacement pile over its full pile length. Fundex piles are usually designed for a 40 to 125 ton service capacity. The method of installation permits no possibility of discontinuities of the pile shaft because a sealant prevents intrusion of soil or water into the incomplete pile. There are no limitations on the depth of the reinforcing cage or rebar size within the pile. There is no central tendon required, and concrete is not soil mixed, but rather pure structural concrete.
Fundex piles are true soil displacement cast-in-place piles. While the operation appears similar to a drilling job, the patented Fundex tip displaces the soil laterally, bringing no spoils to the ground surface. This soil-displacement quality greatly enhances the pile’s capacity over comparably sized conventional drilled shafts.
A cast iron boring tip is fitted to a drilling mandrel by means of a chuck assembly. The mandrel is installed by using torque and down-pressure, producing veryJow noise levels and no vibration. Upon reaching the bearing layer – or upon sufficiently penetrating soil strata in the case of friction pile design – a reinforcing cage is suspended within the mandrel, and concrete is placed. The drill mandrel is then extracted by oscillation thereby leaving the tip, concrete and cage behind in place. In this way, true full section cast-in-place concrete piles are constructed.
The mandrel is 14″ in diameter, and the boring tip is 18″ in diameter. The effective diameter of the completed pile produced is nominally 16 inches. While the Fundex pile is designed for capacities comparable to conventional 14″ Precast driven piles, the cast insitu construction of the piles produces a roughened amplitude surface at the pile-to-sc interface, thereby increasing the frictional capacity of the Fundex piles over other soil displacement piles.
The tip, concrete, and reinforcing are the primary structural elements of the pile. Because the tip is fitted to the mandrel with a drilling chuck and waterproof caulking, there is no concern of soil or groundwater entering the pile mandrel prior to the completion of the pile. Greatly variable depths across a site are achievable as the mandrel may be stopped at any point “refusal” is encountered.
FUNDEX PILES ARE SUITABLE FOR PROJECTS ON WHICH:
- Drilled shafts may be appropriate, but drill spoils are to be avoided
- Space restricts the use of larger diameter drilled shafts, and higher unit friction values are required to develop capacity
- The project space is too confined for conventional precast piledriving
- Noise or vibration is not permissible
- There is a high variability in required pile depths
- Are too remote from precast pile fabricators to economically ship precast piles to the site.
- Auger cast pile construction presents quality control issues
ADVANTAGES OVER PRECAST PILES
- Suitable for projects inaccessible to precast piles due to space restrictions
- Lengths are easily adjusted as required in the field for each pile
- Roughened amplitude of concrete surface affords higher unit friction than smooth pipe or concrete pile
- Installation produces no piledriving noise or vibration
ADVANTAGES OVER DRILLED PIERS
- Running sands, caving or very poor soils, or the presence of a high water table do not affect the installation of Fundex pile.
- Because Fundex piles are displacement piles, the Fundex pile affords a higher unit friction capacity than a comparable drilled shaft
- No materials are conveyed to the surface or are allowed to migrate to deeper strata- a consideration if contaminants are known to exist at a site. Drill spoil offhaul is virtually eliminated.
- Fundex method allows reinforcing cages of any length, and constructs the structural shaft without necking or soil intrusion
ADVANTAGES OVER ACP / ACIP PILES
- Fundex piles are full section soil displacement
- The mandrel prevents intrusion of soil and ground water into the structural elements
- Reinforcing is not limited, nor ‘pushed’ in grout columns. The cage is set prior to concrete placement
- The pile may be fully inspected at any point during installation prior to or during concrete placement. Inspection B does not rely on ‘black box’ interpretation to evaluate the pile shaft. The inspector can literally look down the || shaft to the tip.
FUNDEX PILES PILING WITHOUT VIBRATION
Method of Installation:
A crawler mounted hydraulic piling rig fitted with an hydraulic drill table with 1,5 m stroke Hydraulic pull down.
The drill point complete with a bayonet joint, is attached to a drill tube which in turn is clamped in the drill table.
To commence drilling the drill table is raised to its maximum height and the drill tube is clamped. The drill tube is drilled into the ground with a pull down force on the axis (F = 200 kN) and a torque (var. 120-500 kNm). The ground is displaced, as drilling takes place.
After ensuring that the drill tube is dry, the reinforcing is placed in position and sufficient concrete for the complete pile is poured into the drill tube.
The drill tube is extracted with upward and downward oscillating movements. The drill-point forms an enlarged pile base and stays in the soil.
The pile is completed when the reinforcing cage is placed in position.
TEST PROGRAM FUNDEXPILES
Powerstation Yselcontrole Harculo/Executed by “Delft Soil Mechanics laboratory.”
By using a manometer installed in the hydraulic circuit it is possible to assess the ground resistance by direct comparison with the pressure and it is therefore possible to measure the load bearing capacity of the foundation layer There is a fairly accurate correlation between the pressure shown on the manometer and the cone resistance which has been measured previously.
Because of horizontal displacement and compaction, the cone-resistance of the soil will increase, which has a positive effect on the pilebearing capacity.
Should this system be applied in very weak soils, it is possible to place a prefabricated core or a thin steel casing in the drill-tube after reaching the foundation level. The inner casing is then filled with concrete and the drill-tube extracted.
The space formed by the drill point and the inner-casing or prefabrication core is then filled with grout. When very dense or hard layers have to be penetrated the tube will be drilled by using fluidation. Water is injected through the drill-point around drillpoint and drill-tube. By means of increasing the pore pressure the effective stress of the soil is temporary decreased in order that the drilling’procedure will continue easier.
ADVANTAGES OF THE FUNDEX PILES
- No vibration. No danger to adjacent buildings during drilling. Soil displacement so no decrease of cone resistance and no harm to existing piles.
- Silent operation: The only noise comes from the power pack.
- Speed: The piling rig can be moved on site and quickly erected and made ready for work, thereby providing a high production capacity.
- Bearing capacity: A strong bond between the ground and the pile is created due to the shape of the pile surface, and the soil displacement and compaction.
- Control: The changes in the ground resistance can be monitored by the pressure readings shown on the manometer.
- Economy: There is no superfluous pile length and reinforcement can be light.
- Removal of the ground: The ground is not removed but displaced to the side, so that it compacts and improves.
- Anchor piles: The Fundex pile can be installed to a maximum rake of 1 in 3.
- Bearing capacity: Depending the soil resistance from 1000 to 1250 kN.
- Fundex tension piles: A variation on the system is the Fundex tension pile.
- Method of installation: The drill-tube is provided with a specially designed drill point in which a short reinforcement cage is installed.
When the foundation level is reached, the reinforcement is placed over the anchorcage in the pilepoint, which guarantees sufficient anchor length. The drill-tube can be extracted after placing of concrete. Due to the shape of the pilepoint, the Fundexpiles is very suitable for tension piles.
For piles with high tension, Fundexpiles with prestressed steel bars can be applied, also Tubexpiles (like Fundex but with permanent casing).
Standard sizes of Fundexpiles:
||Drill point diameter:
In special cases, but depending pile length and soil resistance:
||Drill point diameter:
Fundex piles can be constructed at 800 mm from an adjacent building, but in a corner this distances is more.