Hydraulic and earth engineering – Foundation – Columnar structure
Patent
1998-05-28
2000-09-12
Lillis, Eileen D.
Hydraulic and earth engineering
Foundation
Columnar structure
405240, 405233, E02D 534
Patent
active
06116819&
DESCRIPTION:
BRIEF SUMMARY
This invention relates to auger piling, and in particular, but no exclusively, to the automation of the digging and piling phases of continuous flight auger piling operations.
Continuous flight auger piling has been used in the construction industry since the early 1980s. Piles are constructed by drilling to the required depth with a continuous flight auger mounted on a piling rig, withdrawing the auger, and pumping concrete into the excavation through the auger as the auger is withdrawn. A reinforcement cage may subsequently be placed in the wet concrete.
Reliable installation of the pile is influenced by a number of factors. A first consideration is that the ground surrounding the excavation should not be overly disturbed. A second consideration is that sufficient concrete should be delivered through the auger so as to prevent ingress of soil from the walls of the excavation which would otherwise contaminate the concrete cross-section.
With reference to the first of these considerations, it is possible to insert a continuous auger into the ground merely by rotating it with sufficient torque. Under these conditions, lateral displacement of the surrounding soil compacts the soil material, resulting in increased resistance against rotation until the resistance matches the applied torque. At this point refusal occurs, that is, the auger is no longer able to rotate and no further penetration can be achieved. If, at refusal, the auger tip has achieved the required depth and the piling rig is able to withdraw the loaded auger, then it would be possible to deliver the concrete in a straightforward manner. In practice, however, the depth of penetration achieved in this way is rarely sufficient. In order to achieve greater depths, it is possible to limit the rate of penetration of the auger so that soil on the auger flights is gradually sheared from the soil surrounding the excavation.
An auger turning in a soil where there is no peripheral friction will not transport soil upwards and will be very inefficient. An auger turning in a soil with a high angle of friction (this is where the vertical component of the shear force between soil on an auger flight relative to soil comprising the bore wall is large compared to the horizontal component) will have little lateral pressure available from the soil and will therefore be an inefficient transporter. However, an auger turning in a loose sand, for example, is subject to a high lateral soil pressure and will be an efficient transporter. If the penetration rate of the auger in such a soil is not fast enough to keep the auger flights fully loaded from the digging action, the auger will load material by inward failure of the bore wall and cause considerable disturbance to the surrounding ground.
With reference now to the second consideration, namely the delivery of concrete through the auger, it is possible to monitor the concrete feed by determining the concrete pressure in the feed pipe at a suitable location, for example at the top of the auger. A pile may then be installed by maintaining a positive concrete pressure as the auger is withdrawn. This assumes that no additional concrete can be delivered to the void vacated by the withdrawing auger. However, not all ground conditions allow this method to operate reliably. In particular, in badly consolidated soils which allow concrete to escape to the surface, pressure monitoring becomes meaningless. In addition, spoil can block the hole through which the concrete is supplied and result in positive pressure readings although an insufficient amount of concrete is being delivered. Furthermore, the concrete pressure readings are dependent on whether the auger is rotated during withdrawal, since the reading will be reduced if concrete is continually transported up the auger flights. Accordingly, pressure monitoring by itself is not a good technique for controlling pile installation, nor does it provide a good indication of a successfully installed pile.
In order to address these difficulties, it has been proposed, for example i
REFERENCES:
patent: 3200599 (1965-08-01), Phares et al.
patent: 3300988 (1967-01-01), Phares et al.
patent: 4042043 (1977-08-01), Appleman
patent: 4433943 (1984-02-01), Pao Chen
patent: 4958962 (1990-09-01), Schellhorn
patent: 5002435 (1991-03-01), Dupeuble
patent: 5099696 (1992-03-01), Yabuuchi
patent: 5542786 (1996-08-01), Blum
Kvaerner Cementation Fondations Ltd.
Lagman Frederick L
Lillis Eileen D.
LandOfFree
Auger piling does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Auger piling, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Auger piling will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-89892