Today, let us focus on some features and piling technic of steel pile.
1 ,Type and feature of steel pile
- Type
Steel pile used in many projects mainly includes steel sheet piles, shape sheet piles and steel pipe piles.
- Steel sheet pile. There are quite many kinds of steel sheet piles with different shapes of composite interface After the first sheet pile is in position, the second are driven from the first one’s side slot. Thus, groups of sheet piles can form one whole sheet pile wall along the sea coasts or river banks. Sheet pile groups also can be used as cofferdam or temporary retaining measures when digging foundation ditch.
- Shape sheet piles. The most common shape piles is H beam and I beam. H beam and I beam can bear vertical or horizontal loading. The penetration capacity of shape piles is very strong and cause a little ground disturbance, which is also called compaction pile. When the center distance is small, H beam can replace other pre-cast compaction piles in avoid of land upheaval and side compacting during driving.
3) Steel pipe pile. Compared with other types of piles, steel pipe shows advantages on the penetration ability, anti-bending, bearing and lengthening welding.
1.2 Steel pipe piles feature
A, Many specification for choosing.
The pile diameter produced at present is 316mm-2500m, thickness 6.5mm-25mm. Same diameter can be matched with different thickness. Different specification can be used at the same time according to the bearing.
B, Strong bearing.
Most of steel pipes are made of 1% low carbon copper, with strong compression, tensile, shear resistance strength. The good bearing feature will be greatly shown when used in the condition with good bearing layer, thus the single pile bearing capacity greatly improved, pipe quantity and foundation size reduced.
C, Easy length adjustment, high economical effect.
Steel pipe pile is 6m long usually, adopting welding lengthening. When the bearing layer change, it can be cut or welded accordingly. The cut-down section can be welded to another piles, not cause wasting. This measure can also precisely control the pile top elevation.
D, Limited soil compacting.
Steel pipe pile usually adopts open pipes. The soil can be compacted in the pipe, and cause soil plug effect, thus lower the compaction soil and the land surface soil upheaval, reduce soil disturbance and environmental effect. Steep pipes can be used in a limited area with intensive construction.
2, Driving technic
2.1 Construction order arrange.
Before making construction order, please make a full understanding on the project characteristic, geological information, pile feature, pile specification, layout, density, project quantity, working condition, design requirement, project time and used construction machines.
With groups of pipes are driven into the soil, the soil foundation would be compressed, soil density will rise, soil around the pipe will move laterally and vertically, and cause the foundation sink or upheaval with big area. The cross sectional area of steel pipe is small, and the bottom is open. Compared with other solid pipes, the soil compaction quantity is less. However, even these compacting soil would cause pipe position change and damage to the surrounding building and underground pipelines. So it’s very important for pile groups foundation with big quantity and density to arrange the driving order reasonably.
The following is the principle of pile driving order:
For foundation with small quantity or linear foundation: ①Long pipes first then short ones②solid pipes first, then hollowed one③small diameter pipes first, then big diameter ones.
For pipe groups with big quantity and density, besides the above principle, the following should be obeyed: ①the pipes in the center is driven first, then driving peripherally ②driving backwards③The pipes in the return radius of the piling equipment can be arranged at the same time. ④ Piling equipment moves short and less.
2.2 Driving pipes
Pipe stacking
Steel pipes should be stacked carefully. The ground should be flat so the truck can reach directly. The low lying area should be consolidated under the resting point. Drainage ditch should be dug around. The pipes should be stacked with the same specification(upper section pipe, middle section pipe, down section pipe), easy for transit. The stacking point should not cause transformation of the pipes. The stacking layer is normally three, within 2m high. The resting point should use crosstie, and wedged firmly with wood in the two sides in avoid of bottom pipe rolling. When stacking H beam, all the resting point should be arranged in a vertical line. The pipes should be stacked within the piling equipment hoisting area. As the steel pipes are hoisted with one lifting point, all the pipe top should face the piling equipment, and lay as the driving order.
- Steel pipe driving requirement.
- Measure and check every pipe.
- Pile equipment and leader should be vertical. Hammer, pile cap and pipe should be in vertical line, and parallel with leader..
- For special project, leader can be held on in the bottom in avoid of leader tilting when hoisting
- For those pipes with big diameter and easy to be reversed, adjustable hoop should be installed in the leader bottom, especially for H beam. The hoop can
4, Driving through hard soil layer.
In order to fully use the pile strength, the pile length is required to be long enough to reach the deep sand soil layer with N value(standard penetration value) over 50, so the single pile bearing would be improved, and reduce the surrounded building sinking. During the piling of deep and long pipes, piling penetration possibility should be seriously considered as middle hard soil layer is very usual in working condition. According to the capacity of piling equipment and blow bearing of steel pipe, the penetration possibility of piling through hard soil layer can be estimated as follows:
a, For hard soil layer about 20m deep underground, it’s easy to be penetrate it.
b, For sand soil layer with N value over 50 and the thickness is over 5mm, it’s quite difficult to penetrate it.
c, If the subjacent layer under middle hard soil layer is soft soil layer, it’s easy to penetrate the hard layer.
d, Reinforced hoop can be installed in the pile bottom to enhance the penetration possibility.
Yongan Machinery is professional manufacturer of piling equipment with 30 years’ experience, focusing on hydraulic vibratory hammer, hydraulic impact hammer, electric vibratory hammer and excavator mounted hammer. For more information, pls visit: www.yonganpiledriver.com.
Related Reading:Piling Hammers,Machine Piling Hammers,Construction Piling Machines