Device and Method for Improved Pile Casting

Abstract

This invention deals with a device and a method for an improved concrete pile casting in swelling soils by substantially lowering or eliminating heave forces created in active soils from affecting said piles by surrounding selectable parts of the pile by an easily deformable material for lowering the horizontal and the vertical soil movement effect, and by providing a low friction surface for further lowering vertical forces effect. This inventive device and method further facilitates subsequent operations by permitting an easy and seamless casting of columns and by ensuring a clean and smooth pile surface for a better adhesion of new concrete to an old one, as well as preventing cement dough seepage to surrounding soil and concrete segregation.

Description

FIELD OF THE INVENTION[0001]This invention deals with a device for the neutralization, i.d. the lowering or the elimination, of heave forces acting on piles sunk in certain types of expansive soils and for the improvement of the properties of cast in situ piles.BACKGROUND OF THE INVENTION[0002]Certain types of soils, such as clay and marl, swell when absorbing water and shrink when this water is exuded. Water is usually absorbed by soils during the rainy season and exuded by evaporation and the like during the dry season. The shrinkage leads to cracks which can be several meters deep and ten centimeters wide, depending on many factors. The soil depth in which this phenomenon occurs is called the active depth hereinbelow, and may not be uniform. In a rainy season following a dry one, water tends to flow into the cracks and leads to soil swelling, which also closes the cracks, and in the following dry season the soil shrinks to create cracks. Thus an annual soil shrinkage-swelling cyc...

AI Technical Summary

Benefits of technology

[0020]The inner sleeve also supports its weight and that of the other two sleeves. The filling sleeve is intended to be deformed by the horizontal and the vertical forces created by the soil movements, therefore passing only a sma...

Problems solved by technology

The shrinkage leads to cracks which can be several meters deep and ten centimeters wide, depending on many factors.

The soil depth in which this phenomenon occurs is called the active depth hereinbelow, and may not be uniform.

In a rainy season following a dry one, water tends to flow into the cracks and leads to soil swelling, which also closes the cracks, and in the following dry season the soil shrinks to create cracks.

Also, water from other sources, such as water used during construction or for irrigation could flow into soil cracks during a dry season and cause soil swelling.

Both the soil shrinkage and the soil swelling lead to soil movements.

The heave forces act on piles and the like built in active soils, and the pressures, summed over the pile circumference, are known to cause severe structural damage.

The vertical heave forces exceed the design load acting on the pile by low-rise buildings and may exceed the load acting on the pile, in higher / heavier buildings, especially during mid-construction, when the design load is not yet applied.

Desiccation of the soil in the active depth causes pile settlement.

This heave or settlement may be differential among piles, thus leading to cracks in the supported structure.

The horizontal forces may bend, shear and tilt the piles, cracking them and any supported structures.

Either way, damage to the piles and to the supported structures often ensues.

Such collapse fills parts of the borehole with soil and may cause pile shortening, partial concrete filling along some pile sections or even concrete discontinuity with negative structural consequences.

Still another problem caused by the collapse of soil around the bore head is that a roughly inverted conical depression is formed in the collapsed soil region at the upper part of the soil around the bore mouth, and, when filled by concrete, forms a mushroom shaped pile.

This effect is particularly harmful in swelling soils.

Heave forces acting on such mushroom, in addition to their effects elsewhere, may raise the pile, cause tension forces, crack it and the supported structure and lead to other problems.

Yet another problem is the seepage of concrete dough into porous soil such as fill, in contact with the concrete.

This seepage weakens the concrete.

This problem is aggravated when the top part of the concrete is compacted.

No device or method for economically fully solving the abovementioned problems have been developed so far, although partial attempt is shown in GB Patent 2283266 to Sloma.

Such extension is always expensive and often impractical, as bedrock or water table may be encountered.

Of course, this conventional way does not eliminate the heave forces reaching the pile and leading to tension stresses.

These stresses might lead to pile cracking or failure and require added reinforcement.

This conventional solution, as the previous one, is expensive and often impractical.

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