Patent Application
20050129465
The invention relates to a method of construction. In particular, although not exclusively, the invention relates to a method of constructing and installing a structure, such as a building foundation. The method is particularly applicable to forming and positioning foundations on building sites and in particular on sites composed of soft ground material and/or where the effects of water are problematic and/or where extensive excavation would ordinarily be required.
Conventionally, foundations for buildings are often constructed by excavating a site to a required depth, at which, settable material, such as concrete is laid. The foundations may take various forms depending on the composition of the ground on which the building is to be constructed, the design and function of the building and the height to which the building will extend.
In the case of large buildings such as office complexes, skyscrapers and the like, often foundation piles are driven deep into the ground using a variety of known methods and a variety of pile designs, the particular method depending on at least some of the above factors. For example, some piling methods utilise prefabricated pile shafts screwed into the bearing ground layer, such as those disclosed in U.S. Pat. No. 5,697,734 assigned to Beheersmaatschappij Verstraeten B. V.
On sites where the ground is soft and/or there are problems with the presence of water in the area being excavated or where foundation piles are being driven, such as on many coastal sites or sites located near rivers or other bodies of water, piles sometimes have to be driven to incredible depths, and/or very deep excavations made, before a suitable bearing ground layer is reached. This is not only highly inefficient because of the time and expense associated with the need to excavate such huge volumes of material and/or to pile to such depths, but it is also potentially very dangerous for those working on the site. Furthermore, the stability of neighbouring sites and buildings are put at risk because of the inordinately deep excavations and/or piling.
Hence, there is clearly a need for a construction method that addresses or at least ameliorates some, if not all, of the aforementioned problems associated with the prior art construction methods and/or provides a viable commercial alternative to the prior art methods.
In one form, although ft need not be the only or indeed the broadest form, the invention resides in a method of construction including the steps of:
Step c) may further include the step of partially excavating the ground beneath the foundation to temporarily leave at least one supporting region of ground in contact with and supporting the foundation. Suitably, a plurality of such supporting regions may be temporarily maintained beneath the foundation separated by excavated regions of ground.
Dropping of the formed foundation may be guided by the at least one support member and/or a wall of the excavation created in step c).
Suitably, the method includes repeating steps c) and d) until a desired depth for the foundation is reached.
Suitably, prior to performing step c), a structure, such as a wall or the like, may be constructed on one or more sections of the foundation.
Suitably, the at least one supporting member may be a pylon, a pile, a hollow tube, a hollow tube filled with settable material, a H-frame, a beam or the like. Where a plurality of supporting members is employed, one type or a combination of types of supporting members may be employed.
Suitably, the foundation may be formed in one or more segments, at least one support member being provided for each said segment. Preferably, an expansion/contraction joint is provided between adjacent segments of the foundation.
Suitably, the wall created by step c) may be prevented from deflecting by one or more bracing means.
Suitably, a structure, such as a wall, formed on the foundation is prevented from deflecting by one or more bracing means.
Suitably, the bracing means is a bracing member, A-frame, beam or the like.
Where the term “foundation” is used in this specification, it will be appreciated that this term includes structures such as walls and more particularly, walls that may function as a foundation.
Further features of the invention will become apparent from the following description.
To assist in understanding the invention and to enable a person skilled in the art to put the invention into practical effect preferred embodiments of the invention will be described by way of example only with reference to the accompanying drawings, wherein:
In accordance with the present invention and with reference to
Alternatively, the support members 2 may be formed from hollow tubes, such as lightweight cylinders or the like, that are driven or forced into the ground. The hollow tubes may be manoeuvred into position prior to filling the hollow tubes with concrete or other settable material. Such hollow tubes are often used in soft and/or sandy ground.
As yet further alternatives, the support members inserted or otherwise positioned in the ground may be simple beams or H-frames or similar, which are familiar to persons skilled in the art, and may be formed and positioned in the ground according to known techniques.
According to the method of the present invention, a conventional foundation 4 made from, for example, settable material such as concrete, is constructed at the surface 5 of the site adjacent the one or more support members 2 in accordance with known techniques. The foundation 4 may be constructed around the perimeter of the ultimate location of the building, as shown in
Hence, no initial excavation is required prior to laying the foundation and the support members may be formed in the ground to conventional, relatively shallow depths, as discussed below.
With reference to
Once a plurality of regions of earth have been excavated such that foundation 4 is supported by bridges 10 separated by voids 8, support bridges 10 are then initially weakened by partially excavating the support bridges. As the earth of support bridges 10 beneath the foundation 4 is gradually removed, the mass of the foundation above collapses the remaining material of the support bridges 10 causing the level of the foundation to drop in the direction of the arrows shown in
If the foundation is to be dropped to, for example, about 3 metres below the surface, supporting members 2 may be formed in, or otherwise inserted into, the ground to a depth of, for example, about 6 metres below the surface 5. The aforementioned specific depth to which the earth is excavated therefore corresponds to the new depth to which the foundation will be dropped. It will be appreciated that the method of the invention is not limited to these depths.
The above excavation process may then be repeated to drop the foundation to a greater depth if required. This process can be continued until the desired foundation depth is achieved. As the depth of excavation increases, bracing means such as supporting braces or bracing members 22, A-frames (not shown), beams or the like may be used to prevent walls 9 of the excavation adjacent the foundation, from deflecting. Walls 9 are shown in
The width of supporting bridges 10 and the number thereof beneath the foundation 4, or sections of foundation, will depend on the dimensions and composition of the foundations and on the composition of the ground. Where harder ground material is present, the supporting bridges can afford to be narrower than the width of supporting bridges required with softer ground material. It will be appreciated that the method of the invention is not limited to support bridges 10 and/or voids 8 being of the same dimensions or being at regular intervals. These may differ according to, for example, ground conditions and foundation dimensions.
The size of supporting bridges 10 may also increase with depth. For example, for a section of concrete foundation about 2 metres long and about 1.5 metres wide to be dropped to a depth of about 3 metres, a supporting bridge of, for example, approximately 1 metre wide and the same width as the foundation 4, located about the midpoint of the foundation, may be sufficient to support that section of foundation, depending on the composition of the ground material. If the foundation is to be dropped to greater depths, the width of supporting bridges 10 will need to be increased.
Excavation of the supporting bridges may be facilitated by the use of suitably shaped excavating buckets (not shown). Such a bucket may have a width approximately the same as that of the supporting bridge with a substantially triangular cross-sectional shape. The shape of the bucket is such that more of the earth of the supporting bridges is removed at shallower depths closer to the foundation 4 than at deeper depths further away from the foundation. This causes the material of the supporting bridges to initially collapse closer to the foundation where the supporting bridge is weaker. The collapsing material to be excavated is then pushed out away from beneath the foundation. This method is particularly appropriate where the ground material is hard and potentially difficult to excavate.
With reference to
It will be appreciated that on larger, or awkwardly shaped sites, it could be difficult to excavate evenly around the perimeter foundation, which could lead to, for example, cracking in the foundation if it were unevenly or uncontrollably dropped. Therefore, in accordance with the present invention and with reference to
The earth beneath the foundation of each segment can be excavated, as described above, at its own rate, independent of the excavation rate of other segments on the site if necessary. The foundations of each segment can then be dropped when the excavation in that segment is ready, thus allowing each segment of the site to proceed at its own rate. This avoids progress on the whole site being hindered by, for example, excavation difficulties encountered in only one other segment.
It will be appreciated by persons skilled in the art that although four supporting members 2 per foundation segment are shown in
The method of the present invention addresses the aforementioned problems of the prior art in that it is not necessary that supporting members 2 be driven to incredible depths from the surface 5 of the site. The foundation 4, wall 12 or the like only needs to be constructed at the surface 5 and dropped to the desired depth relative to, and guided by, the supporting members and the excavation itself.
Furthermore, excavation of the site is hugely simplified because only comparably small volumes of material need to be excavated at one time from the site to enable the foundation to be lowered a prescribed distance, before repeating the process as necessary. This avoids the prior art danger of having to excavate large volumes of material at one time, which increases the risk of collapse of the ground, the risk being amplified by the presence of soft/sandy ground material and/or the presence of water.
The method of the present invention is more rapid than prior art methods because time is not wasted in driving piles, pylons or the like from the surface 5 to great depths. Supporting members 2 only need to be driven or otherwise inserted into the ground to a depth that is sufficient to support dropping of the foundation 4 to, for example, the first or second new level, which may occur at, for example, 3 metres and 6 metres respectively. If the foundation is to be dropped further, the supporting members can then be driven further into the ground. However, the supporting members will be further inserted from a level that is already, for example, 3 metres or 6 metres below the surface 5, making the piling or similar process easier.
Excavation of the ground material is also assisted by the mass of the foundation 4 and any structure built thereon, such as walls 12, pressing down on the ground material, which helps force the ground material out from beneath the foundation.
The present invention could be applied to the preparation and installation of structures such as walls, foundations and the like, for a wide range of constructions. The present invention is particularly useful for the foundations of tall buildings that require substantial foundations, especially in locations with soft and/or sandy require substantial foundations, especially in locations with soft and/or sandy conditions and/or where the presence of water is a problem.
The present invention is also particularly applicable for the construction of underground car parks and the like, which are ubiquitous in modern buildings.
Throughout the specification the aim has been to describe the invention without limiting the invention to any one embodiment or specific collection of features. Persons skilled in the relevant art may realize variations from the specific embodiments that will nonetheless fall within the scope of the invention. For example, additional guiding means may be provided to provide further control over the descent of the foundation and increase safety of the method. For example, foundation 4 may be coupled to one or more support member 2, such as with a cable or the like coupled to foundation 4 and to a collar, the collar adapted to slide up and down support member 2 to restrain descent of the foundation once supporting bridges 10 have been removed.
| Number | Date | Country | Kind |
|---|---|---|---|
| PS 0960 | Mar 2002 | AU | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/AU03/00274 | 3/7/2003 | WO |
