Prestressed pipe piles have the same shortcomings as ordinary pipe piles.
- Diesel hammer with a pipe pile, the vibration, noise, squeeze soil volume, will cause a certain degree of environmental pollution and impact. However, the use of static pressure method of construction, no vibration, no noise, but the squeezing effect is still there.
- Pile pile depth is limited, in the deep foundation pit excavation truncated after pile more, but the static pressure method construction, send pile depth can increase, more than pile less.
- Some geological conditions, such as limestone for the bearing layer, in the “soft under the hard, hard and soft mutations,” the geological conditions, should not use hammer method construction.
1. Water impulse method
Pile tip set high pressure water nozzle. High-pressure water jet loosens the soil and loosens the soil and rock, reduces the resistance of the pile tip and reduces the friction between the pile surface and the buckle, which makes it easy to pile and reduce the damage of pile and equipment.
2. Pre – drilling method
Pre-drilling can reduce soil resistance:
It is generally effective to drill a hole having a diameter of about 30 cm at the center of the pile width or to loosen the soil with a twist drill.
This method is applicable to soils where it is difficult or impossible to construct steel sheet piles (H-piles, box-piles or pipe piles).
Common Blasting: Explosion creates a V-shaped groove in the pile wall. Piling conditions in loose soil areas are still difficult, as it is recommended to strengthen the pile tip.
Impact Blasting: The solid rock into fine particles, but does not move it, the impact of the rock is small.
Prestressed pipe piles not only have the same advantages as ordinary pipe piles, but also possess some advantages not possessed by other pipe piles due to their own characteristics.
- Single pile bearing capacity is high. Prestressed concrete pile pile strength is high, and some up to 80MPa, and can enter the dense sand and strong weathering layer, the pile tip into the strong weathering layer or dense sand layer, after a strong squeeze, near the tip of the pile Strong weathered layer or dense sand layer is not the original state, pile end bearing capacity can be 80-100% increase than the original, so the design value of pile bearing capacity than the same diameter cast-in-place pile or bored pile, such as Φ100- 500 pile, the maximum design bearing capacity used to 2700kN, equivalent to Φ600 and Φ700 of the drill (red) bored piles.
- Wide selection of design options. Pipe pile specifications, the general manufacturers can produce Φ300-Φ600 pipe piles, individual can also produce Φ800 and Φ1000 pipe pile; single pile bearing capacity from 600kN to 4500kN, both for multi-storey building, but also for 50 layers below High-rise building, but also in the same building foundation, but also according to the size of the column load with different diameter pipe piles, pile design is easy to solve the problem, but also give full play to the maximum bearing capacity of each pile, and pile settlement Uniform.
- And it has strong adaptability to geological conditions with large fluctuation of bearing layer. Because the pipe pile section length is short, commonly used 10-12m section, there are 15-16m section, there are 4-5m, 6-7m short section, with a flexible, convenient section, at the construction site at any time according to geological conditions Changes in the amount of adjustment section pile length, saving the amount of pile, not like ordinary precast concrete square pile as prone to lack of pile length or pile phenomenon.
- The bearing capacity of single pile is cheap. It is unscientific to compare the economic value of the pile with the cost per meter or the cost of the concrete. The comparison is made by the bearing capacity of the unit (per ton or per KN). Although the cost per meter pipe pile than the sinking of the pile, but the bearing capacity of a single pile is high, the resulting cost per tonne bearing capacity is still cheaper than the immersion pile; although the cost of concrete pipe pile than the man-made digging pile and pile , But the bearing layer than the manual digging pile and bored pile shallow, so the cost per ton bearing capacity under normal circumstances is still cheaper than digging pile and bored pile, in general, the prestressed pipe pile unit The cost of bearing capacity in many pile type is a cheaper one.
- Transport lifting convenient, then pile fast. Pile section length is generally less than 13m, there are prestressed pile, lifting hook with a special hook at both ends of the pipe pile can be easily suspended. Then take the pile welding method, if the use of two welders work together, Φ500 of the pile, a connector about 20 minutes or so can be welded.
- Pile length is not limited by construction machinery. As the pile with a flexible, piles can be long or short length, unlike the sinking cast-in-place by the construction machinery restrictions, not the same as manual dug pile, pile length limited by geological conditions.
- Pipe pile construction speed, short construction period. Mainly in the following three aspects: a) pre-construction preparation time is short, PHC pile from production to use the shortest time only 3-4 days; b) construction speed, a 2-3 million m2 building area of high-rise building , A month or so will be able to complete the pile; c) detection time is short, 2-3 weeks to test the inspection is completed.
Steel Pipe Piles are also designed to transfer structural loads through the foundation to soils below. Where H-Piles are typically classified as point bearing, Pipe Piles are most efficient as friction piles. Pipe Piles have substantial surface area that interacts with the surrounding soil to provide great frictional load resistance.
Pipe Piles are also used in conjunction with sheet piles to add lateral stiffness and bending resistance where loads exceed the capacity of sheet piles alone.
ERW Pipe Piling
Electric Resistance Weld (ERW) pipe is manufactured through individual sheets or from rolls of skelp.
DSAW Pipe Piling
Double Submerged Arc Weld pipe (DSAW) is created through a welding process in which the welding arc is immersed in flux at the time of welding. Double welds (both inside and outside the pipe) are required to manufacture this pipe, and generally each weld is completed separately.
Spiralweld Pipe has a joint running along it’s entire length in a spiral form. Due to the manufacturing process, a wide variety of diameters can be produced.
(This article comes from R.W. CONKLIN STEEL editor released)
The present study investigates the behaviour of plug on pile load capacity and effect of plug removal. The sand used as a foundation soil is poorly graded clean sand. It was prepared at different densities using a raining technique. To simulate the pile load test in the field, a new apparatus was manufactured. A driving–pressing system for pile installation was manufactured. The soil plug is removed by a device manufactured to remove the soil column entrapped inside the pipe piles during installation by driving and pressing devices. The present study focuses on the determination of effect of soil plug on the ultimate compression capacity of single open-ended steel pipe pile, and makes a comparison with closed-ended pipe pile. A new type of pipe piles is suggested; it is closed–open-ended pipe piles driven and pressed into sandy soil of different densities (medium and dense) in which axial compression load tests were performed on model piles. The pile end will be open to a predetermined depth in order to make pile penetration easy and closed at a distance in order to increase the pile base resistance. Twenty-four models of open-ended piles have been modified by closing the pile ends by a plate welded at a distance of 2D, 3D and 4D(where D is the diameter of the pile) from tip of the pile. These piles have been installed in sand by two types of installation, driving or pressing. It was concluded that the pile load carrying capacity in dense sand is several times greater than those in loose and medium sands, especially in the case of closed-ended or open-ended piles, since the pipe pile can produce external and internal skin friction in addition to end-bearing resistance that makes the total pile capacity close to that of closed-ended pile. On the other hand, the removal of soil plug decreases the pile load capacity. This decrease becomes apparent in dense sand. The decrease in load capacity is about 45%–63%, 55%–63% and 51%–79% in loose, medium and dense sands, respectively. Open-ended pipe piles behave as closed-ended, if the soil plug formed inside piles in a state of partial plug or full plug. The length of soil plug depends on the type of installation and relative density.
For the type of pile proposed in this study, open-ended piles are closed with a plate welded at a distance of 2D, 3D and 4D from the tip of the pile, and the open part of the pipe pile has a limited length, which was found to be 3D. This length revealed the maximum pile capacity due to the development of both interior and exterior skin friction in addition to end resistance. In addition, at this length, the soil column is pressed inside the pipe and hence the soil was densified leading to increase the skin resistance.
(This article comes from tandfonline.com editor released)
Prior to the placing of concrete in a closed end pipe pile, the pile shall be inspected by an acceptable method to confirm the full pile length and dry bottom condition. If accumulations of water in pipes are present for either closed end or open end pipes, the water shall be removed before the concrete is placed.
The concrete for concrete filled pipe piles shall have a minimum compressive strength of 2.5 ksi (17.3 MPa) and a slump of not less than 6 inches (150 mm) and not more than 10 inches (250 mm). Concrete shall be placed in each pile in a continuous operation.
No concrete shall be placed until all driving within a radius of 15 feet (4600 mm) of the pile has been completed, or all driving within the above limits shall be discontinued until the concrete in the last pile cast has set for at least two days.
A drop light or mirror system, or weighted tape with attached dry cloth are possible inspection methods.
It is not necessary to use a tremie or centering cone when placing concrete in pipe piles. It is impossible to center the concrete in a batter pile.
Continuous operation may include changing of concrete supply trucks or other brief interruptions.
(This article comes from PILE DRIVING CONTRACTORS ASSOCIATION editor released)