WO2016077891A1

WO2016077891A1 - Construction screw pile

Info

Publication number: WO2016077891A1
Application number: PCT/AU2015/050734
Authority: WO
Inventors: Grant Macdonald
Original assignee: Tristanagh Pty Ltd
Priority date: 2014-11-20
Filing date: 2015-11-20
Publication date: 2016-05-26
Also published as: AU2015349623A1

Abstract

A construction screw pile including an elongate tubular body having a cutting assembly at a lower end thereof, and at least one helical flight provided on the body and a drive assembly at an upper end of the body to facilitate rotation of the screw pile to drive the screw pile into the ground, wherein the elongate tubular body is provided with a number of spaced apart openings therethrough.

Description

CONSTRUCTION SCREW PILE

TECHNICAL FIELD

[0001] The present invention relates to a construction screw pile and particularly to a construction screw pile configured for different uses in different stages of the construction.

BACKGROUND ART

[0002] Construction screw piles are conventionally available, as are dewatering apparatus to remove excess water from a bore prior to insertion of a structural screw pile.

[0003] Typically, the methodology of inserting a structural screw pile is to screw the pile into the earth. The structural screw pile typically has an elongate shaft made of hollow, round structural steel pipe with one or more helixes over the length of the shaft in order to screw the pile into the earth. The lower wall leading end of the shaft may be cut at 45° in order to assist installation.

[0004] Drive lugs are typically provided at an upper end of the shaft in order to engage with a drive machine in order to rotate the screw pile during insertion.

[0005] The screw pile is normally driven into the earth, and because the screw pile is hollow, earth normally collects in the hollow shaft of the screw pile. This earth is normally augured out of the shaft in order that the shaft can be filled with concrete as groundwater is difficult to collect with earth filling the body of the pile and the body cannot be filled with concrete if earth fills the body. A pile cap is normally formed on an upper end of the screw pile in order to connect the pile to a structure's foundation. Normally, metal reinforcing bars (starter bars) are cast into the piles and protrude out into the footing of the building which is poured at an upper end of the screw pile.

[0006] Screw piles differ from ground anchors in that ground anchors are normally used on a much smaller scale, and typically driven in by hand or using a rotator bar through an eyelet provided at an upper end of the ground anchor. The technology used in the creation of ground anchors is much simpler than structural screw piles as the ground anchors are normally only used in soil, and are not required to bear large loads and are typically not machine driven.

[0007] One of the problems in using structural screw piles is an accumulation of

groundwater at a lower end of the screw pile. Normally, operators have a dewatering apparatus which typically consists of a pipe which is connected to a vacuum pump in order to remove water from the hollow shaft of the screw pile. This system can generally only works well if there is sufficient water in the hollow shaft of the screw pile.

[0008] It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

SUMMARY OF INVENTION

[0009] The present invention is directed to a construction screw pile, which may at least partially overcome at least one of the abovementioned disadvantages or provide the consumer with a useful or commercial choice.

[0010] With the foregoing in view, the present invention in one form, resides broadly in a construction screw pile including an elongate tubular body having a cutting assembly at a lower end thereof, and at least one helical flight provided on the body and a drive assembly at an upper end of the body to facilitate rotation of the screw pile to drive the screw pile into the ground, wherein the elongate tubular body is provided with a number of spaced apart openings therethrough.

[0011] The screw pile of the present invention will typically facilitate the efficient establishment of deep groundwater wells, as well as allowing dewatering of a screw pile and formation of permanent foundation construction piles, not only to an appropriate bearing surface but also into rock if required. The screw pile of the present invention also facilitates an improved mechanism to increase the engagement of the screw pile with the surrounding ground elements through the application of concrete or grout under pressure that can penetrate the surrounding ground material through the openings provided in the body of the screw pile. The present invention also allows a single screw pile to be used as a ground dewatering system during the early stages of earthworks in construction and then to be used as a permanent foundation pile in order to mount a structure relative thereto.

[0012] The preferred embodiment of the present invention preferably includes a number of components including a main, elongate tubular body, a base plate, a cutting head, at least one helical flight and a drive assembly at an upper end of the screw pile (not to be confused with the mating drive assembly for driving the screw pile).

[0013] The elongate tubular body is preferably manufactured of a metal, and normally of steel. The tubular body is elongate. The body may be formed of a single part, or multiple parts may be connected together longitudinally in order to form the body. If multiple parts are attached together, normally mating flanges are provided through which there are openings which, when aligned, can receive fasteners to attach one body portion to another body portion.

[0014] According to a particularly preferred embodiment, the screw pile of the present invention may have a lower or terminal end as described herein as the screw pile and one or more elongate tubular bodies of a similar configuration but without openings through the body, located above the screw pile of the present invention.

[0015] Typically, the elongate tubular body is substantially circular in cross-sectional shape. Generally, the tubular body is between 300 mm and 600 mm in diameter. Preferably, the elongate tubular body will have a rigid and strong construction and preferably, the metal wall thickness is at least 3 mm in thickness up to 15 mm in thickness, but normally between 3 mm and 6 mm in thickness.

[0016] Preferably, the elongate tubular body of the screw pile of the present invention is provided with a closed forward end. Normally, the forward end is closed by the provision of a base plate. The base plate is generally thicker than the wall thickness of the tubular body given that the base plate will normally encounter high loads during insertion. According to a preferred embodiment, the base plate has a thickness of approximately 10 mm, although this could vary depending upon the diameter of the elongate tubular body. Normally the base plate is made of metal, and typically the same metal as the tubular body.

[0017] The base plate is preferably fixed in the end of the tubular body, normally at the end of the tubular body. The fixing mechanism will be chosen according to the materials involved, but will normally be welding given the metals involved. The base plate will preferably prevent ingress of material into the forward end of the body thereby keeping the elongate tubular body of the screw pile substantially empty of earth and rock which may have otherwise been forced thereinto during insertion of the screw pile.

[0018] The screw pile of the present invention includes a cutting assembly provided at a lower end of the elongate tubular body. Typically, different cutting assemblies or cutting heads can be used depending upon the ground conditions and/or the purpose of the pile. According to the present invention, three alternative cutting head types can be provided, namely a soil cutting head, rock cutting head and a combination of soil and rock head.

[0019] The soil cutting head is typically provided as a substantially planar head or blade that includes a number of peaks thereon. Normally the peaks are oriented away from the elongate body. Any number of peaks may be provided, but the particularly preferred embodiment includes three peaks. The peaks are normally generally triangular in shape and are normally formed in a unitary configuration with the head or blade. Generally, a planar plate is cut or otherwise provided with the preferred number and configuration of peaks.

[0020] It is preferred that the peaks provided on the soil cutting head are asymmetrical. Normally, a central peak is provided which has a pair of edges oriented at equal angles to one another. A pair of lateral peaks are provided outside the central peak, but the lateral peaks typically differ in configuration to the central peak and to each other. One of the lateral peaks will preferably be formed by providing a single leading-edge only with the remaining edge being the lateral edge of the head or blade. The other of the preferred lateral peaks will preferably have a pair of leading edges albeit of different lengths which thereby creates an asymmetrical pattern.

[0021] Preferably, the central peak extends further forwardly than the lateral peaks, with one of the lateral peaks extending further forwardly than the other. (Note: the "forward" direction is in the direction of insertion into the ground)

[0022] The soil cutting head preferably diverges laterally beyond the dimension of the elongate tubular body, but preferably only by a small distance. The cutting head is therefore approximately the same dimension at the root of the cutting head as the elongate tubular body but wider at its widest point.

[0023] Normally the soil cutting head is welded to the base plate fitted to the elongate tubular body and preferably extend substantially perpendicularly to the base plate. If no base plate is provided, the cutting head is typically welded to the terminal end edge of the tubular body, typically with some form of bracing provided.

[0024] The rock cutting head of the preferred embodiment preferably uses rock cutting tips which may be specifically shaped or manufactured for that purpose. For example, the rock cutting tips may have a particular shape and/or they may be hardened and/or provided with a wear resistant coating.

[0025] Typically, each of the rock cutting tips is attached or otherwise mounted to a substantially triangular plate which extends forwardly from the elongate tubular body in a manner similar to the soil cutting head. The rock cutting tips are typically smaller than those provided on the soil cutting head. The rock cutting head is typically used when there is no intermediate soil and the pile is driven directly into rock. [0026] The combination soil and rock head is typically used if the pile is required to be driven into rock strata lying beneath a soil layer. In this configuration, normally sacrificial rock cutting tips are welded to the soil cutting head. This preferably allows the pile to be driven through the soil overburden and then into the rock strata.

[0027] The screw pile of the present invention includes one or more helical flights. Each helical flight attached to the elongate body in order to provide downward pressure to force the screw pile into the ground as it is rotated by the driving head. The diameter and pitch of the helical flights is typically designed for each application, that is, a helical flight is customised to optimise performance for the conditions and outcomes sought for each application.

[0028] For typical soil applications, the helical flight is approximately 200 mm greater in diameter than the elongate tubular body and has a pitch of approximately 100 mm.

[0029] Generally, the helical flight is manufactured from metal and typically, from the same type of metal as the body and cutting head. The helical flight is typically manufactured as an annular ring that has been opened by being cut laterally. Typically, the ends of the helical flight will have a particular shape, formed by the cut used to open the annular ring. Normally, the leading end of the helical flight will have a tip or point formed by cutting the annular ring open using two different angled cuts that intersect one another. The opposite end of the helical flight will therefore have a chevron shape.

[0030] Normally, a first helical flight will preferably be connected directly to an external surface of the elongate tubular body immediately behind the cutting head. As mentioned above, one or more additional helical flights may be provided over the height of the screw pile but this will be dependent upon the material through which the screw pile is inserted.

[0031] A flange is typically provided at an upper end of the elongate tubular body.

Preferably the flange will extend radially from the end of the tubular body. The flange preferably is an annular plate with the radius of the inner opening matching the diameter of the elongate body. The outer diameter of the pipe can vary depending upon the pipe's dimension and the flange will typically match the outer diameter of the pipe.

[0032] The flange will preferably be provided with a number of openings spaced about the flange. Preferably, the openings are drilled through the flange at approximately 30° separation.

[0033] The flange preferably extends substantially perpendicularly to the elongate body and may be supported by one or more gussets, typically four gussets. The gussets are generally trapezoidal in shape with an edge to abut the outer surface of the elongate body, a substantially perpendicular upper edge of the substantially perpendicularly edge and an angled outer edge which angles from approximately the dimension of the flange back towards the elongate body.

[0034] The thickness of the flange and of the gussets will typically vary from between 10 mm to 20 mm depending upon the conditions and that the application of the pile. The gussets will normally be welded directly to the flange and the external surface of the elongate body to brace the flange against both longitudinal load and circumferential load.

[0035] The screw pile of the present invention includes a drive assembly at an upper end of the body to facilitate rotation of the screw pile to drive the screw pile into the ground through engagement with a mating drive assembly. The drive assembly normally includes a driving head which has a driving flange that matches the pile flange. Typically, the driving flange is similar in all respects to the pile flange. The driving flange may have fewer openings. According to a preferred embodiment, the driving flange has a number of openings through the flange which alternate with male spigots, the openings and the spigots corresponding in number and position to the openings on the pile flange. The provision of the male spigots allows alignment of the drive flange with the pile flange through insertion of the male spigots through the openings in the pile flange. Fasteners such as high tensile bolts are typically placed through the remainder of the aligned openings of the pile flange and drive flange.

[0036] The elongate tubular body is provided with a number of spaced apart openings therethrough. The openings can have any shape and configuration and any number of openings can be provided. Typically, the openings are either slots extending radially about the elongate tubular body or circular openings through the body.

[0037] Where provided in the slot configurations, the openings are optimised for the use of the pile as a deep dewatering well whilst the circular holes are optimised for extrusion of grout and/or concrete under pressure into the surrounding ground material once the pile is in place.

[0038] The openings are typically provided in a regular pattern on the body. Openings may be provided in the base plate, but if so, are generally provided with covers on the outside of the base plate such that it is difficult to force material through the openings in the base plate from the outside during insertion, but material can be forced through the openings from the inside of the pile as required.

[0039] Where provided as slots, each slot is typically approximately 100 mm in length by 1 mm in height. The slots are typically arrayed in a spaced apart configuration radially around the circumference of the body.

[0040] A number of sets of openings can be provided spaced over the height of the body. Typically, the openings do not extend completely over the height of the body with an upper section of the body will normally being opening free. The openings typically begin a short distance above the upper end of the helical flight.

[0041] The screw pile of the present invention may be used with a grout placement cap. In order to place grout under pressure through the screw pile and to maximise the penetration of the grout into the surrounding rock and soil strata, a special purpose cap matching the pile flange is preferably fitted to the top of the pile to allow grout insertion. Typically, a sealing member is used between the grout placement cap and the pile flange.

[0042] The grout placement cap preferably includes a grout inlet pressure valve which connects to an elongate conduit made of either steel or PVC located within the hollow interior of the screw pile to allow the grout to be inserted into the screw pile under pressure. The cap also preferably has a pressure release valve in order to allow displaced water, air and impurities to escape.

[0043] If there is groundwater present under pressure, the grout placement cap may be a single use item so that the whole system can be sealed whilst the grout cures. In this case, openings may be provided in the cap for the placement of reinforcing starter bars in order to allow pile cap to be formed thereon. Normally, grout is prevented from escaping through these holes by means of a simple flap placed over the holes on the inside of the grout placement cap.

[0044] The abovementioned construction screw pile when used as a dewatering well and in a preferred form includes a steel pipe with a bottom cutter and helix to enable it to be screwed into the ground, and a top flange and gussets to allow a hydraulic machine to be attached to apply a torque. The steel pipe has slots cut into it which allow groundwater to flow into the centre of the pipe. It is normally installed by first screwing a larger diameter plain steel pipe with an external auger flight into the ground to the required depth. This pipe can then be cleaned out with a standard flight auger, and backfilled with clean gravel. The larger diameter pipe is then removed, leaving a vertical cylinder of gravel in the soil. The construction screw pile of the present invention can then be screwed into the gravel, a submersible pump is lowered to the bottom and the pipe capped off forming the dewatering well.

[0045] This system works extremely well but, on occasions, can become blocked. This can occur for a number of reasons: 1. Fine soil particles (silt and clay) blocking the pores in the gravel layer;

2. Fine soil particles (silt) blocking the slots cut into the dewatering well pipe; and/or

3. Deposition of salts from the groundwater building up around the slots.

[0046] Therefore, when used as a dewatering well, the construction screw pile of the present invention may further be provided with an external annular screen around the slotted pipe to prevent larger objects abutting the exterior of the slotted pipe. The annular screen will preferably be spaced from the exterior of the slotted pipe to define an annular space therebetween.

[0047] A dispersion assembly may be provided within the preferably annular space between the annular screen and the slotted pipe. The dispersion assembly will preferably include at least one manifold, upper and/or lower and a number of dispersion elements, preferably tubes or the like with one or more openings therein extending from or between the manifolds. The one or more openings may be provided with shaped openings or nozzles to aid in dispersion and/or maintaining pressure. Each manifold may also be provided with one or more openings therein. The one or more openings therein are all preferably directed at least partially inwardly at the slotted pipe. Each opening can be aligned with or directed at a slot in the slotted pipe. The dispersion assembly will therefore also preferably be annular and may be attached or mounted to the external annular screen.

[0048] A vertical riser can be connected to at least one of the manifolds and, at the surface, this may be divided into different branches, preferably three, each with a separate valve. Should the system become blocked as described above, combinations of air, water and solvent can be applied under pressure through the valves and into the vertical riser, to be expelled from the one or more openings in the dispersion elements.

[0049] The air and water would be used to blast the blocked material through the slots, where it will be sucked up by the pump and discharged at the surface. Once the material is loosened the air flow will be reduced and the water flow increased to create sufficient flow for the pump. If there is build-up of salts then other solvents can be added through the third pipe to help to remove them.

[0050] Once the dewatering is completed and the extraction of groundwater is no longer required, it is also be possible to:

1. remove the submersible pump;

2. clear out any residue from the dewatering pipe; and

3. tremie concrete into the pipe with any necessary reinforcement and use the whole as a permanently steel cased cast-in-place foundation pile.

[0051] Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention.

[0052] The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.

BRIEF DESCRIPTION OF DRAWINGS

[0053] Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows:

[0054] Figure 1 is an isometric view of a construction screw pile according to a particularly preferred embodiment of the present invention.

[0055] Figure 2 is a side elevation view of the construction screw pile illustrated in Figure 1.

[0056] Figure 3 is a plan view of a screw pile flange according to a preferred embodiment of the present invention.

[0057] Figure 4 is a side elevation view of a cutting head according to a preferred embodiment of the present invention.

[0058] Figure 5 is a side elevation view of a gusset according to a preferred embodiment of the present invention.

[0059] Figure 6 is a plan view of a bottom plate according to a preferred embodiment of the present invention.

[0060] Figure 7 is a plan view of a helical flight according to a preferred embodiment of the present invention.

[0061] Figure 8 is a plan view of the construction screw pile as illustrated in Figure 1.

[0062] Figure 9 is an isometric view of a construction screw pile in dewatering mode according to a further aspect of the present invention.

[0063] Figure 10 is a sectional view of the construction screw pile illustrated in Figure 9 along line A-A.

[0064] Figure 10 is a detailed, partially sectional view of the configuration illustrated n Figure 9.

DESCRIPTION OF EMBODIMENTS

[0065] According to a particularly preferred embodiment of the present invention, a construction screw pile 10 is provided.

[0066] According to the illustrated embodiment, the construction screw pile 10 includes an elongate tubular body 11 having a cutting head 12 at a lower end thereof, and a helical flight 13 provided on the body 11 and a drive assembly 14 at an upper end of the body 11 to facilitate rotation of the screw pile 10 to drive the screw pile 10 into the ground, wherein the elongate tubular body 11 is provided with a number of spaced apart openings 15 therethrough.

[0067] The elongate tubular body 11 of the illustrated embodiment is manufactured of steel. The body 1 lof the screw pile lOis formed in a single part, but other tubular bodies (not shown) may be connected together longitudinally in order to locate the screw pile 10 at a required depth.

[0068] The elongate tubular body 11 is substantially circular in cross- sectional shape.

Generally, the tubular body is between 300 mm and 600 mm in diameter. The wall thickness is at least 3 mm in thickness up to 15 mm in thickness, but normally between 3 mm and 6 mm in thickness.

[0069] In one embodiment, the elongate tubular body 11 of is provided with a closed forward end by the provision of a base plate 16. The base plate 16 is generally thicker than the wall thickness of the tubular body 11 given that the base plate 16 will normally encounter high loads during placement of the screw pile 10. According to a preferred embodiment, the base plate 16 has a thickness of approximately 10 mm although this could vary depending upon the diameter of the elongate tubular body. Normally the base plate is made of metal, and typically the same metal as the tubular body. The base plate 16 is fixed in the lower end of the tubular body 11 by welding.

[0070] The cutting head 12 is provided at a lower end of the elongate tubular body 11 as illustrated in Figures 1 and 2. Different cutting heads can be used depending upon the ground conditions and/or the purpose of the pile. According to the present invention, three alternative cutting head types can be provided, namely a soil cutting head, rock cutting head and a combination of soil and rock head but only the soil cutting head is illustrated in the Figures.

[0071] The soil cutting head is illustrated in detail in Figure 4. This head is provided as a substantially planar blade that includes a number of peaks thereon oriented away from the elongate body 11 as illustrated in Figure 2. The peaks of the illustrated embodiment are generally triangular in shape and are normally formed in a unitary configuration with the blade. Generally, a planar plate is cut or otherwise provided with the preferred number and configuration of peaks.

[0072] The peaks provided on the soil cutting head illustrated in Figure 4 are asymmetrical. The central peak 17 has a pair of edges oriented at equal angles to one another. A pair of lateral peaks are provided outside the central peak 17, but the lateral peaks differ in configuration to the central peak and to each other. One of the lateral peaks 18 is formed by providing a single leading-edge 19 only with the remaining edge being the lateral edge 20 of the cutting head 12. The other of the lateral peaks 21 has a pair of leading edges 22, 23 of different lengths which thereby creates an asymmetrical lateral peak 21.

[0073] As illustrated, the central peak 17 extends further forwardly than the lateral peaks 18, 21 with one of the lateral peaks 21 extending further forwardly than the other 18. (Note: the "forward" direction is in the direction of insertion into the ground)

[0074] The soil cutting head also extends laterally beyond the dimension of the elongate tubular body 11, but preferably only by a small distance. In other words, the lateral edges 20 of the cutting head are oriented at a small angle outwardly from the tubular body 11. The soil cutting head is welded either to the base plate 16 fitted to the elongate tubular body 11 and preferably extend substantially perpendicularly to the base plate 11 or alternatively, can be fixed to the end edge of the tubular member 11 if there is no base plate provided.

[0075] A helical flight 13 is attached to the elongate body 11 in order to provide downward pressure to force the screw pile 10 into the ground as it is rotated by the driving head (not shown). The diameter and pitch of the helical flight 13 is typically designed for each application, that is, it is customised to optimise performance for the conditions and outcomes sought for each application.

[0076] For typical soil applications, the helical flight 13 is approximately 200 mm greater in diameter than the elongate tubular body 11 and has a pitch of approximately 100 mm. [0077] Generally, the helical flight 13 is manufactured from metal and typically, from the same type of metal as the body 11 and cutting head 16. As illustrated in Figure 7, the helical flight 13 is typically manufactured as an annular ring that has been opened by being cut laterally.

According to the illustrated embodiment, the ends of the helical flight 13 have a particular shape, formed by the cut used to open the annular ring. Normally, the leading end of the helical flight will have a tip or point formed by cutting the annular ring open using two different cuts that intersect one another. The opposite end of the helical flight will therefore have a chevron shape.

[0078] The helical flight 13 of the illustrated embodiment is connected directly to an external surface of the elongate tubular body 11 immediately behind the cutting head 12.

[0079] The drive assembly of the illustrated embodiment includes a pile flange 24 provided at an upper end of the elongate tubular body 11 and as illustrated in Figures 3 and 8. The pile flange 24 extends radially from the end of the tubular body 11 and is an annular plate with the radius of the inner opening 25 matching the diameter of the elongate body 11. The outer diameter of the elongate body can vary and the flange 24 will typically match the outer diameter of the elongate body.

[0080] The flange 24 is provided with a number of openings 26 spaced about the flange 24 at approximately 30° separation.

[0081] The flange 24 extends substantially perpendicularly to the elongate body 11 and is supported by four gussets 27. The gussets 27 illustrated in Figure 1 and 2 are rectangular whilst the preferred embodiment is illustrated in Figure 5 in which the gussets are trapezoidal in shape with an edge 28 to abut the outer surface of the elongate body 11, a substantially perpendicular upper edge 29, a substantially perpendicularly lower edge 30 and an angled outer edge 31 which angles from approximately the dimension of the flange 24 back towards the elongate body 11.

[0082] The thickness of the flange 24 and of the gussets 27 will typically vary from between 10 mm to 20 mm depending upon the conditions and that the application of the pile. The gussets 27 will normally be welded directly to the flange 27 and the external surface of the elongate body 11 to brace the flange 24 against both longitudinal load and circumferential load.

[0083] The screw pile of the present invention is typically used with a drive assembly attachable to the flange at the upper end of the body to facilitate rotation of the screw pile to drive the screw pile into the ground. The drive assembly normally includes a driving head which has a driving flange that matches the pile flange. Typically, the driving flange is similar in all respects to the pile flange. The driving flange may have fewer openings. According to a preferred embodiment, the driving flange has a number of openings through the flange which alternate with male spigots, the openings in the spigots corresponding in position to the openings on the pile flange. The provision of the male spigots allows alignment of the drive flange with the pile flange through insertion of the male spigots through the openings in the pile flange. Fasteners such as high tensile bolts are typically placed through the remainder of the aligned openings of the pile flange and drive flange.

[0084] A lower portion 32 of the elongate tubular body 11 is provided with a number of spaced apart openings 15 therethrough. The openings 15 can have any shape and configuration and any number of openings can be provided.

[0085] In the preferred embodiment, the openings are slots optimised for the use of the pile as a deep dewatering well whilst circular holes are optimises for extrusion of grout and/or concrete under pressure into the surrounding ground material once the pile is in place.

[0086] As illustrated in Figure 2, the slot openings 15 are provided in a regular pattern on the body 11. Each slot opening is typically approximately 100 mm in length by 1 mm in height. The slot openings 15 are typically arrayed in a spaced apart configuration radially around the circumference of the body. A number of sets of openings can be provided spaced over the height of the lower portion 32 of the body. The openings 15 do not extend completely over the height of the body 11 with an upper section 33 of the body 11 being free of openings. The openings 15 typically begin a short distance above the upper end of the helical flight 13.

[0087] The screw pile of the present invention may be used with a grout placement cap. In order to place grout under pressure through the screw pile and to maximise the penetration of the grout into the surrounding rock and soil strata, a special purpose cap matching the pile flange is preferably fitted to the top of the pile to allow grout insertion. Typically, a sealing member is used between the grout placement cap and the pile flange.

[0088] The grout placement cap preferably includes a grout inlet pressure valve which connects to an elongate conduit made of either steal or PVC located within the hollow interior of the screw pile to allow the grout to be inserted into the screw pile under pressure. The cap also preferably has a pressure release valve in order to allow displaced water, air and impurities to escape.

[0089] If there is groundwater present under pressure, the grout placement cap may be a single use items so that the whole system can be sealed whilst the grout cures. In this case, openings may be provided in the cap for the placement of reinforcing starter bars in order to allow pile cap to be formed thereon. Normally, grout is prevented from escaping through these holes by means of a simple flap placed over the holes on the inside of the grout placement cap.

[0090] The use of the construction screw pile of the present invention is also important.

[0091] When the screw pile is to be used for dewatering, it is typically placed as a deep well. After the ground conditions and proposed ground works have been carefully studied, the position and depth of the screw pile can then be established. For this purpose, the screw pile will typically extend at least 3m below the maximum elevation of the groundwater which is present. The screw pile for this purpose is normally provided with slot openings around the body at horizontal centres of approximately 150 mm and vertical centres of separation between adjacent sets of openings of approximately 75 mm. The screw pile is typically inserted into the ground into a bore and is surrounded with relatively fine stone or gravel. A submersible pump with an automatic water level sensor is typically placed within the hollow body of the screw pile and connected to a conduit to pump the water out of the screw pile body.

[0092] The ground in which the dewatering well is formed using the screw pile is to be placed, is preferably prepared by means of a large auger which is driven into the ground to the full depth of the proposed groundwater well. This breaks up the ground to allow the placement of the outer casing of the dewatering well in the form of the screw pile of the present invention.

[0093] The screw pile of the present invention is then preferably driven into the ground. It is particularly preferred that the screw pile used in this particular configuration is an open bottom screw pile without a base plate. If depths of greater than 6 m are required, one or more extension pipes are attached to the screw pile, using the pile flange and a mating flange on the extension pipes until the screw pile is driven to the full depth of the proposed well.

[0094] A smaller auger is typically then inserted into the hollow interior of the elongate body and is used to remove any soil within the casing to the full depth of the proposed well.

[0095] Typically, the hollow interior of the screw pile body is then filled with gravel or stone, typically relatively fine, washed gravel. Once the interior of the screw pile body has been filled with the gravel or stone, the screw pile is then removed by reversing the direction of rotation to screw the pile out of the ground.

[0096] A screw pile is then preferably screwed back into the ground through the gravel or stone. The helical flight pitch will typically be set to push the gravel outwards into the surrounding soil. As the screw pile is driven downwardly, additional gravel is typically added about the pile body to ensure that the pile body remains completely surrounded by gravel or stone. The gravel or stone will typically prevent the openings in the body from becoming clogged with soil fines and therefore maximise the drainage surface area between the well system and the surrounding soil.

[0097] Once the screw pile is properly located within the gravel or stone, a submersible pump with a fixed water level sensor is placed approximately 300 mm from the bottom of the pile. This is typically connected by means of a one-way valve to one or more dewatering conduits which can in turn be connected to a dewatering header line.

[0098] Screw piles can be used for foundation purposes as well, and these typically rely on end bearing and surface skin friction. The pile must typically provide resistance against compressive downward pressure and also uplift pressure from groundwater or other forces. Further, traditional piles driven into weak rock strata can cause cracking within the rock strata, fundamentally reducing the rock's ability to withstand the uplift pressures. The screw pile of the present invention differs fundamentally from other screw piles because it cuts its way through the soil and the rock via the preferred cutting tips and therefore, tends not to fracture the rock. It is designed to penetrate into and through class four rock and it dramatically increases the bond between the screw pile in the surrounding soils at rock by pressure injection of grout through the openings in the pile body and/or the base plate.

[0099] When the screw pile of the present invention is to be used as a structural pile, again, the ground conditions, direct site observations and requirements stipulated by the project structural and geotechnical engineers are considered. Once all the required information has been analysed, the screw pile will then normally be designed particularly for the job to be undertaken. That is the diameter of the elongate body and the length of the pile will be calculated, a cutting head chosen, the details of the helical flights, pile wall thickness, base penetration and grout placement are all determined for each particular pile location. Individual piles are then typically made and delivered to site which are uniquely tailored to particular locations.

[0100] The particular pile locations are generally located precisely and are marked. In some circumstances, in order to aid pile penetration and to increase the bond with the surrounding ground strata as well as filling ground voids, grout may be placed using a grout swivel system as the pile is screwed into the ground.

[0101] Once the pile is in place, the preferred grout placement cap is secured to the top of the screw pile via the pile flange. If high groundwater pressures are anticipated, this will be a single use cap as it will be required to remain in place to resist the pressures of the groundwater whilst the grout cures. In other situations, the grout placement cap will be a reusable cap. The preferred grout placement cap preferably incorporates a tremie pipe which extends more or less to the bottom of the pile as well as a pressure release valve.

[0102] A tremie concrete placement method uses a tremie pipe, through which concrete is placed below water level. The lower end of the tremie pipe is preferably maintained immersed in fresh concrete so that the rising concrete from the bottom displaces the water without washing out the cement content.

[0103] The grout is pumped under pressure to the bottom of the pile via the tremie pipe, forcing the water, air and impurities above it. This typically continues until all of the impurities are purged and the grout is observed coming out through the release valve. At this point, grout placement ceases and the pressure release valve is typically sealed.

[0104] Once the grout placement has been completed, the reinforcing bars (starter bars) are typically placed into the grout either through holes made in the grout placement cap for this purpose or once the grout placement cap has been removed.

[0105] If a site requires dewatering via deep wells, then these wells can be placed at structural pile locations specified by a project structural engineer. The screw pile of the present invention can then be designed so that it can initially act as a dewatering well as described above and once dewatering is no longer required, grout can then be placed relative to the screw pile as described in the structural application above, transforming the screw pile from a dewatering pile into a permanent structural pile. In this configuration, the pile will typically be specifically designed, manufactured and placed so that it complies with both a dewatering and structural functions.

[0106] When used as a dewatering well, the construction screw pile may further be provided with an external annular screen 40 around the body 11 in the area of the body 11 having the slot openings 15 to prevent larger objects abutting the exterior of the body and blocking the openings 15 as illustrated in Figures 9 to 11. The annular screen 40 will preferably be spaced from the exterior of the body 11 to define an annular space therebetween. The annular screen will normally have a solid upper portion 41 and a solid lower portion 42 and a capping ring 43 at both ends.

[0107] As illustrated in Figures 9 to 11, a dispersion assembly may be provided within the annular space between the annular screen 40 and the body 11. The dispersion assembly of the illustrated embodiment includes an upper manifold 44 and a number of dispersion tubes 45 extending therefrom, each dispersion tube 45 having one or more openings therein. The openings may be provided with shaped openings or nozzles to aid in dispersion and/or maintaining pressure. The manifold 44 may also be provided with one or more openings therein. The openings therein are all preferably directed at least partially inwardly at the body 11. Each opening can be aligned with or directed at a slot 15 in the body 11. The dispersion assembly will therefore also preferably be annular and may be attached or mounted to the external annular screen 40.

[0108] A vertical riser 46 can be connected to the manifold 44 and, at the surface, this may be divided into different branches 47, preferably three as illustrated, each with a separate valve to allow injection of air, water and/or solvent (or combinations thereof). Should the system become blocked as described above, air, water and/or solvent (or combinations thereof) can be applied under pressure through the valves and into the vertical riser 46, to be expelled from the one or more openings in the dispersion tubes 45.

[0109] The air and water would be used to blast the blocked material through the slots 15, where it will be sucked up by a submersible pump 48 and discharged at the surface. Power will normally be supplied to the pump and a discharge conduit will normally be provided in an umbilical 49 as shown in Figure 11 in particular. Once the material is loosened the air flow will be reduced and the water flow increased to create sufficient flow for the pump 48. If there is build-up of salts for example, then other solvents can be added to help to remove them.

[0110] Once the dewatering is completed and the extraction of groundwater is no longer required, it is also be possible to:

1. remove the submersible pump 48;

2. clear out any residue from the dewatering pipe; and

3. tremie concrete into the pipe with but preferably without any reinforcement and use the pile 10 as a permanently steel cased cast-in-place foundation pile.

[0111] In the present specification and claims (if any), the word 'comprising' and its derivatives including 'comprises' and 'comprise' include each of the stated integers but does not exclude the inclusion of one or more further integers.

[0112] Reference throughout this specification to 'one embodiment' or 'an embodiment' means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases 'in one embodiment' or 'in an embodiment' in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

Claims

1. A construction screw pile including an elongate tubular body having a cutting assembly at a lower end thereof, and at least one helical flight provided on the body and a drive assembly at an upper end of the body to facilitate rotation of the screw pile to drive the screw pile into the ground, wherein the elongate tubular body is provided with a number of spaced apart openings therethrough.

2. A construction screw pile as claimed in claim 1 wherein the body is formed of a lower or terminal end having an elongate tubular body, at least one helical flight on the body and a number of spaced apart openings and one or more elongate tubular bodies without openings through the bodies connected together longitudinally in order to form a pile body using mating flanges provided through which there are openings which, when aligned, can receive fasteners to attach one tubular body to another tubular body.

3. A construction screw pile as claimed in claim 1 or claim 2 wherein, the elongate tubular body is provided with a closed forward end.

4. A construction screw pile as claimed in any one of the preceding claims including a cutting assembly provided at a lower end of the elongate tubular body chosen depending upon the ground conditions and/or the purpose of the pile.

5. A construction screw pile as claimed in any one of the preceding claims wherein each of the number of spaced apart openings are slots extending radially about the elongate tubular body

6. A construction screw pile as claimed in any one of claims 1 to 4 wherein each of the number of spaced apart openings are circular openings through the body.

7. A construction screw pile as claimed in any one of the preceding claims wherein the number of spaced apart openings are provided spaced over the height of the body.

8. A construction screw pile as claimed in any one of the preceding claims wherein used as a dewatering pile.

9. A construction screw pile as claimed in 8 further including an external annular screen

around the body adjacent the number of openings to prevent larger objects abutting the exterior of the slotted pipe.

10. A construction screw pile as claimed in 9 wherein the external annular screen is spaced from an exterior of the body to define an annular space therebetween.

11. A construction screw pile as claimed in 10 wherein a dispersion assembly is provided within the annular space between the annular screen and the body, the dispersion assembly including at least one manifold, and a number of dispersion elements to disperse material injected.

12. A construction screw pile as claimed in 10 wherein a vertical riser is connected to the at least one manifold, the vertical riser extending to the surface, to allow material to be applied under pressure into the vertical riser, to be expelled from one or more of the dispersion elements.

13. A method of dewatering an ground area using a dewatering pile, the dewatering pile

including an elongate tubular body having a cutting assembly at a lower end thereof, and at least one helical flight provided on the body and a drive assembly at an upper end of the body to facilitate rotation of the dewatering pile to drive the dewatering pile into the ground, wherein the elongate tubular body is provided with a number of spaced apart openings therethrough, the method including the steps of driving the dewatering pile into the ground, installing a pump into the body with an outlet at an upper end of the body in order to pump water that enters the body through the number of spaced apart openings our of the body.

14. A method of dewatering a ground area using a dewatering pile as claimed in claim 13

wherein a larger diameter pipe with an external auger flight is driven into the ground to the required depth prior to driving the dewatering pile into the ground.

15. A method of dewatering a ground area using a dewatering pile as claimed in claim 14

wherein larger diameter pipe is cleaned out, and backfilled with particulate material, the larger diameter pipe then removed, leaving a core of particulate material in the ground.

16. A method of dewatering a ground area using a dewatering pile as claimed in claim 15

wherein the dewatering pile is then screwed into the core of particulate material, a pump lowered thereinto and the dewatering pile capped.

17. A method of forming a foundation pile in a ground area, the foundation pile including an elongate tubular body having a cutting assembly at a lower end thereof, and at least one helical flight provided on the body and a drive assembly at an upper end of the body to facilitate rotation of the foundation pile to drive the foundation pile into the ground, wherein the elongate tubular body is provided with a number of spaced apart openings therethrough, the method including the steps of driving the foundation pile into the ground, and injecting grout thereinto and allowing the grout to cure.

18. A method of forming a foundation pile in a ground area as claimed in claim 17 wherein a grout placement cap is secured to the top of the foundation pile and a tremie pipe which extends more or less to the bottom of the foundation pile is used to inject grout.

19. A method of forming a foundation pile in a ground area as claimed in claim 17 or claim 18 wherein once the grout injection has been completed, one or more reinforcing bars are placed into the grout prior to curing.

0. A method of dewatering a ground area as claimed in any one of claims 13 to 16 and then forming a foundation pile using the method claimed in any one of claims 17 to 19.