Method for sheet pile installation

Abstract

A method for preaugering and preparing a pile line in weathered rock on a construction site, comprising the steps of; defining a central line relating to where the sheet piling is to be installed; aug

Description

METHOD FOR SHEET PILE INSTALLATION Field of the Invention This invention relates to a new method for sheet pile installation on a construction site. Background of the invention Pre-augering is an ancillary technique used within the sheet piling industry to pre-treat the ground prior to sheet pile installation by effectively loosening the ground into which the sheet pile is to be installed. Pre-augering is a relatively basic technique which can provide significant cost effective benefits to a sheet pile solution. The current industry method of pre-augering involves ‘screwing’ either a 450mm diameter or 600mm diameter auger into the ground at either 600mm or 750mm centres respectively with a 7.0Te maximum torque auger motor. The method is an 'open hole' technique which means only the auger flight is ‘screwed’ into the ground and no casing is provided using an 'open hole' augering method. The auger is simply screwed into the ground and back wound once the design level has been achieved with no flighting of material occurring. The process leaves a column of loosened material along the pile line. For a long time the inventors of this application have been aware of the limitations of the current pre-augering methods adopted in the sheet piling industry particularly when pre- augering is done to facilitate sheet pile installation into Weak or Weathered Rock . Itis known that weak or weathered rock typically has the following parameters: Extrapolated SPT (standard penetration test) value of 150-500, and Uniaxial compressive strength of 50-400N / mm? The technique has the advantage of allowing sheet piles to be installed into ground conditions which would otherwise prove too hard or dense to allow sheet pile installation. Also, by modifying the ground in advance, this allows a lighter sheet pile section to be used on the project. The problem which exists with the technique is that since it is an ‘open hole’ method, a residual shoulder of un-augered material remains between the auger holes. This is required in order to prevent the auger trying to deviate back into the previously augered hole. Figures 1(a) to (d) show different prior art piling arrangements using Z-piles and U- piles. Figure 1(a) shows a plan view of Z-piles inserted into auger holes 102, 104, 106, 108, alternate holes are offset from reference line 110, with holes 102, and 106 having centres along a common central line above reference line 110, and holes 104 and 108, having the centre along a different common central line below reference line 110. As shown, the distance between the centres of adjacent holes is 630mm, and each hole has a diameter of 450mm. Z-piles 120, 122, 124 are inserted so that adjacent holes are connected by the 2Z-pile. Typically the vertical sections of the Z-pile will go along vertically along the central diameter of the holes, and the central sloped section of the Z-pile connecting the two vertical sections is positioned close to the circumference of the auger holes, and then extends in the region between adjacent auger holes to end closed the the circumference of the adjacent auger hole. Figure 1(b) shows a plan view of U-piles 150 with auger holes 132, 134, 136, 138, with a 450mm diameter. The centre of all of holes 132, 134, 136 and 138 are aligned on central line 110. As shown, the distance between the centres of adjacent holes is 630mm, and each hole 132, 134, 138 and 138 has a diameter of 450mm. Each of the holes is connected to the adjacent hole by a U-shaped pile 150. The pile 150 has a vertical section 152, with two sloping sides 154, extending away from the vertical section to produce a U- shape, where the top open section is typically larger than the base 152. As shown, the U- shaped piles 150 are alternately arranged with the vertical section 152 on a first side of a first auger hole, and the vertical section 152 for a the adjacent pile 150 on the opposing side of the adjacent hole, with the sloping sides of adjacent U-piles meeting in approximately in the centre of the augur hole. Figure 1(c) shows the use of Z-piles with auger holes with a 600mm diameter and a separation of 750mm between the centre of adjacent auger holes, In this case the auger holes 160, 162, 184 and 166 all have their centre along common central line 170. A shown, the Z-piles 120, 122, 124 and 126 re arranged in a similar fashion to those of figure 1(a). In this arrangement, the areas between the auger holes are shoulder regions 172. These are residual shoulders of unaugered material that prevent the installation of the sheet pile. Figure 1(d) shows the use of U-piles with auger holes with a 600mm diameter. This is similar to the arrangement as shown in figure 1(h) except that the diameter of the auger holes is 600mm, and the separation between the centre of adjacent holes is 750mm. Although the shoulders 172 are only shown in figure 1(c), these will result in all of the different sheet piling arrangements as shown in figures 1(a)-(d). It is this shoulder of remaining un-augered material which causes significant sheet pile installation problems particularly when trying to install sheet piles into Weak or Weathered Rock. With this in mind and on stich projects, the only current solution to the problem would be the options discussed below. :- Alternative solutions include a contiguous or secant pile wall. However, these solutions are much more expensive and time consuming than a sheet piling solution. Figure2(a) shows an example of contiguous piling holes produced by the open-hole method. As shown, there are three structural piles 10, 12 and 14, with variable pile spacing between the three piles. As described above, the ‘open hole' technique which means only the auger flight is 'screwed' into the ground and no casing is provided using an ‘open hole’ augering method. The auger is screwed into the ground and the material removed / flighted to form an open hole. This process basically leaves an open hole along the pile line which is then infilled with concrete and reinforcing bar between each of piles 210, 212 and 214. Utilise a cased augering system used for forming a secant wall to carry out the pre- augering. Secant pile walls are formed by constructing intersecting reinforced concrete piles. Secant pile walls are reinforced with either steel rebar or with steel beams and are constructed by drilling under mud. Primary secant piles are installed first with secondary reinforced secant piles constructed in between primary piles once the latter gain sufficient strength. Pile overlap is typically in the order of 3 inches (8 cm). In a tangent pile wall, there is no pile overlap as the piles are constructed flush to each other. The advantages of secant pile walls are: increased construction alignment flexibility, increased secant pile wall stiffness compared to sheet piles, easier to install in difficult ground, construction is less noisy. An example of a secant wall formed in this way is shown in figure 2(b). In stage 1, a series of pile holes 220, 222, 224, 226, and 228 are formed. Each of these holes will receive an unreinforced primary pile. In stage 2, secondary holes 230, 232, 234, 236 are formed between the primary piles, and then a reinforced secondary pile is inserted into the secondary holes. Typically, the unreinforced piles are usually installed first and consist of cement / bentonite or weak concrete. The reinforced piles are then installed in stage 2 and the reinforcement can be either cages or I-beams. Secant walls are typically used for enabling and supporting excavations. supporting wing walls, water cut off for drainage channels and slope stabilization. However, this technique is extremely time consuming and can only be undertaken using small diameter casing typically between 473mm- 810mm diameter, with a maximum auger torque of 15Te. According to the invention there is provided a method for preaugering and preparing a pile line in weathered rock on a construction site, comprising the steps of: defining a central line relating to where the sheet piling is to be installed; auguring a first circular basis hole of a first series of basis holes, with a diameter of x mm at a first position, with the centre of the first circular basis hole positioned on the central line; where the material in the first circular basis hole is loosened by the augering but not removed from the first circular basis hole; auguring a second circular basis hole of the first series of basis holes with a diameter of x mm, with the centre of the second circular basis hole on the central line, where the separation, y, between the centre of the first and the second circular basis hole is given by 1 Xsys 12 x mm; where the material in the second basis hole is loosened by the augering but not removed from the first circular basis hole; repeating the auguring step for the first series of basis holes (n-2) times, to produce a series of n circular basis holes, all with centres along the central line, where the separation between each successive basis hole of the first series is given by 13x sys 12x mm; where the material in each successive basis hole is loosened by the augering but not removed from each successive basis hole; augering a first circular basis hole of a second series of basis holes with a diameter of x mm , where the first circular basis hole of the second series is located between the first and second holes of the first series of basis holes, with a centre on the central line, so that the circumference of the first circular basis hole of the second series of basis holes overlaps with the circumference of the first and second basis holes of the first series of basis holes to form a first lens overlap between the first hole of the first series of basis holes and the first hole of the second series of basis holes, and a second lens overlap between the first hole of the second series of basis holes and the second hole of the first series of basis holes ; where the material in the first circular basis hole of the second series of basis holes is loosened by the augering but not removed from the basis hole; repeating the auguring step for the second series of basis holes (n-1) times, to produce a second series of n circular basis holes, where the material in each basis hole of the second series of basis holes is loosened by the augering but not removed from the basis hole; where the nth circular basis hole of the second series is located between the nth and n+1th basis hole of the first series of basis holes, so that the circumference of the nth circular basis hole of the second series overlaps with the circumference of the nth and n+1th basis holes of the first series of basis holes, so that the basis holes of the first and second series of basis holes are arranged alternately, and they is a lens shaped overlap between every adjacent basis hole inserting sheet piling between the first basis hole of the first series of basis holes, and the first basis hole of the second series of basis holes, and repeating the sheet piling insertion, so that the sheet pile installation extends from the first hole of the first series of basis holes through all the holes in the first and second series of basis holes, where the sheet piling is inserted into the loosened material in each of the basis holes Preferably, the sheet piling to be inserted is Z shaped sheet piling. In a preferred embodiment of the invention, the central line is a substantially vertical line. Preferably, x is between 500mm-1200mm. Preferably, the preaugering is done into a rock substrate. Further preferably, the rock substrate is weathered sandstone with an SPT value between 300-600. Further preferably, the augering steps are performed at a maximum torque of 30T. Preferably, the lens overlap between adjacent holes of the first and second series of basis holes has a maximum value of 200 mm. Further preferably, the lens overlap has a maximum value of 150mm. In a preferred embodiment of the invention, n is as least 4. In a further embodiment of the invention there is also provided a method for the installation of sheet piling comprising: preaugering a pile line as described above, inserting sheet piling into the preaguered pile line. By the term 'piling' we mean a support which may be used as a deep foundation to transfer and distribute loads through ground material or stratum (e.g. soil) with inadequate bearing, sliding or uplift capacity to more solid ground material located at a depth with a higher bearing, sliding or uplift capacity and more capable of supporting a load. Suitably, a piling may be constructed from steel, concrete, timber and other metals. Preferably, a piling comprises steel, including reinforced steel, or concrete. By the term ‘displacement piling’ we mean a piling as defined herein which is driven into the ground and ground material is displaced essentially simultaneously. By the term ‘replacement piling’ we mean a piling as defined herein which is inserted (e.g. driven) into a hole in the ground and ground material is not displaced essentially simultaneously. By the term ‘sheet piling’ we mean a piling which is essentially in the form of sheet material. The sheet material may comprise different shapes, dimensions and configurations. Other optional and preferred features of the invention are set out in the dependent claims, and the description, below. The features of one aspect of the invention can be combined in any complimentary manner, with one or more features of another aspect of the invention, the dependent claims, and / or with one or more features of the description, where such a combination of features would provide a working embodiment of the invention. Brief Description Of The Drawings The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views, which together with the detailed description below are incorporated in and form part of the specification and serve to further illustrate various embodiments of concepts that include the claimed invention, and to explain various principles and advantages of those embodiments. FIG 1(a) illustrates an example of pre-auguring using Z-piles known from the prior art. FIG 1(b) illustrates an example of pre-auguring using U-piles known from the prior art. FIG 1(c) illustrates an alternative example of pre-auguring using Z-piles known from the prior art FIG 1(d) illustrates an alternative example of pre-auguring using U-piles known from the prior art. FIG. 2(a) illustrates an example of contiguous wall piling, as known from the prior art. FIG. 2(b) illustrates an example of secant wall piling, as known from the prior art. FIG. 3(a) shows an example of a first stage of pre-auguring according to an embodiment of the invention: FIG. 3(b) shows an example of an intermediate stage of pre-auguring according to an embodiment of the invention; FIG. 3(c) shows an example of a final stage of pre-auguring according to an embodiment of the invention; FIGs 4A and 4B show a flow chart for a method of operation according to an embodiment of the invention. FIG 5 shows an example of a drilling rig used in an embodiment of the invention. Detailed Description of the invention The new improved method adopted in this invention to overcome the problems discussed above, was to utilise a high torque piling rig set up in 'open hole' or 'CFA" mode to effectively pre-auger the pile line using a 900mm diameter auger which would be drilled on a 'hit and miss' basis at 1500mm centres. Preferably, the drilling rig that is used to carry out the process of this invention is summarised below:- - Bauer BG33 Rotary Drilling Rig - CFA Drilling Mode utilised. - Maximum drilling torque = 28Te - Maximum drilling depth = 21.0m Although other drill rigs may also be used if they operate in CFA mode with the maximum torque and depth as specified above. Figure 5 shows an example of the drill rig 500, as used in this invention. The drill rig comprises undercarriage 501, upper carriage 502, main winch 503, kinematic system 506, mast 507, mast head 508, Kelly bar 509, rotary drive (KDK) 510 and drilling tool 511. The skilled person in the art would be aware of how this device would operate to generate a pile, and so this will not be describe in great detail, however, we refer to https: / / www.ecanet.com / uploads / files / Resources / BG 33 H BT 85 PremiumLine EN 905 791 2.pdf which provides more information about the operation of the drilling rig. Continuous flight auger (CFA) piles are drilled in one continuous operation enabling much faster installation time than for bored piles. Reinforcement is placed into the wet concrete after casting, enabling the pile to resist the full range of structural loading. Typical uses of CFA piling include: providing structural support, providing earth retention, especially on site boundaries or close to adjacent buildings, prevent landslides or protect existing buildings and are often combined with other techniques such as ground anchors or soil nails CFA piles are typically constructed by rotating a hollow stem continuous flight auger into the soil to a designed depth. Concrete or grout is pumped through the hollow stem, maintaining static head pressure, to fill the cylindrical cavity created as the auger is slowly removed. The reinforcement cage is placed through the freshly placed concrete. With reference to Figure 3(a), , it can be seen that by augering with a 900mm diameter auger on a 'hit and miss’ basis of alternate holes sites; the complete sheet pile line can be effectively pre-augered without leaving any shoulders or un-augered rock which would prove problematical to sheet pile installation. In this way, the pre-augered material is not removed from the alternate hole sites, but is loosened so that sheet piles can be inserted into the loosened material. Preferably, the construction site comprises a series of holes 1,2, 3,.....n, all aligned along a central line. Preferably, the central line is a substantially vertical line. In a preferred embodiment of the invention, the diameter of each of the series of holes 1...n is between 500-1200mm. Further preferably, the rock substrate to be pre- augered is weathered sandstone with an SPT value between 300-600. Specifically in an embodiment of the invention, in the pattern as shown in figure 3(a), a first series of basis holes 310, 312, 314, 316 and 318.... are sequentially preaugered using a 900mm diameter auger at 1.5m centre to centre for successive holes. This preaugering will loosen the material within the drilled region, without the material being removed from the drilled region. The sheet piling can then be easily inserted into the loosened material in the pile, without the need for removal of the material (flight mode), and insertion of material such as concret or grout into the drilled region. . The position of the sheet piling is also indicated at 370, 372, 374, 376, 378, 380 and 382. In an embodiment of the invention, the sheet piling is Z-shaped sheet piling. Preferably, the sheet piling is not inserted until the preaugering has been completed as shown in figure 3(c). In an embodiment of the invention, the process then returns as shown in figure 3(b). In this stage the “missed” holes, specifically second series of basis holes 320, 322, 324 are also pre-augered using the same 900mm diameter at 1.5m c / c. The material in the drilled region of each of the holes 320, 322, 324 of the second series of basis holes is not removed from the hole, as it typically would in flight mode, but is loosened, so that the sheet pile can be easily inserted into the drilled region of hole 320, 322, 324. As shown, the distance between the centre of holes 310, 312, 314, 316 and 318 as created in stage 1, and between the centre of the holes 320, 322, 324 as created in the second stage is 1500mm, and the overlap between adjacent augur holes, in oval regions 350, 352, 354, 356, 358, 360, 360 has a maximum width of 150mm. Figure 3(c) shows the arrangement when the second stage has been completed, and all of the preauger holes have been created, and the sheet piling has been inserted, into the loosened material in the drilled regions, without the need for concrete or other grout material. Fig. 4(a) and (b) is a flowchart of an example process 400. In some implementations, one or more process blocks of Fig. 4(a) and (b) may be performed by a device . As shown in Fig. 4(a), process 400 may include defining a central line relating to where the sheet piling is to be installed (block 402) on the construction site. Preferably, the sheet piling is to be inserted into weak or weathered rock.. For example, device may define a central line relating to where the sheet piling is to be installed, as described above. As also shown in Fig. 4, process 400 may include auguring a first circular basis hole of a first series of basis holes, with a diameter of x mm at a first position, with the centre of the first circular basis hole positioned on the central line (block 404). For example, device may augur a first circular basis hole of a first series of basis holes, with a diameter of x mm at a first position, with the centre of the first circular basis hole positioned on the central line, as described above. As further shown in Fig. 4, process 400 may include auguring a second circular basis hole of the first series of basis holes with a diameter of x mm, with the centre of the second circular basis hole on the central line, where the separation, y, between the centre of the first and the second circular basis hole is given by 114 x = y < 145 x mm (block 406). For example, device may augur a second circular basis hole of the first series of basis holes with a diameter of x mm, with the centre of the second circular basis hole on the central line, where the separation, y, between the centre of the first and the second circular basis hole is given by 114 x = y < 145 x mm, as described above. As also shown in Fig. 4, process 400 may include repeating the auguring step for the first series of basis holes (n-2) times, to produce a series of n circular basis holes, all with centres along the central line, where the separation between each successive basis hole of the first series is given by 114 x <y < 145 x mm (block 408). In a preferred embodiment of the invention, n is at least 4. For example, device may repeat the auguring step for the first series of basis holes (n-2) times, to produce a series of n circular basis holes, all with centres along the central line, where the separation between each successive basis hole of the first series is given by 114 x <y < 145 x mm, as described above. As further shown in Fig. 4, process 400 may include augering a first circular basis hole of a second series of basis holes with a diameter of x mm , where the first circular basis hole of the second series is located between the first and second holes of the first series of basis holes, with a centre on the central line, so that the circumference of the first circular basis hole of the second series of basis holes overlaps with the circumference of the first and second basis holes of the first series of basis holes to form a first lens overlap between the first hole of the first series of basis holes and the first hole of the second series of basis holes, and a second lens overlap between the first hole of the second series of basis holes and the second hole of the first series of basis holes (block 410). For example, device may auger a first circular basis hole of a second series of basis holes with a diameter of x mm , where the first circular basis hole of the second series is located between the first and second holes of the first series of basis holes, with a centre on the central line, so that the circumference of the first circular basis hole of the second series of basis holes overlaps with the circumference of the first and second basis holes of the first series of basis holes to form a first lens overlap between the first hole of the first series of basis holes and the first hole of the second series of basis holes, and a second lens overlap between the first hole of the second series of basis holes and the second hole of the first series of basis holes, as described above. As also shown in Fig. 4, process 400 may include repeating the auguring step for the second series of basis holes (n-1) times, to produce a second series of n circular basis holes, where the nth circular basis hole of the second series is located between the nth and n+1th basis hole of the first series of basis holes, so that the circumference of the nth circular basis hole of the second series overlaps with the circumference of the nth and n+1th basis holes of the first series of basis holes, so that the basis holes of the first and second series of basis holes are arranged alternately, and they is a lens shaped overlap between every adjacent basis hole (block 412). Process 400 may also include the step of inserting sheet piling between the first basis hole of the first series of basis holes, and the first basis hole of the second series of basis holes, and repeating the sheet piling insertion, so that the sheet pile installation extends from the first hole of the first series of basis holes through all the holes in the first and second series of basis holes, where the sheet piling is inserted into the loosened material in each of the basis holes (block 414). For example, an augering device may repeat the auguring step for the second series of basis holes (n-1) times, to produce a second series of n circular basis holes, where the nth circular basis hole of the second series is located between the nth and n+1th basis hole of the first series of basis holes, so that the circumference of the nth circular basis hole of the second series overlaps with the circumference of the nth and n+1th basis holes of the first series of basis holes, so that the basis holes of the first and second series of basis holes are arranged alternately, and they is a lens shaped overlap between every adjacent basis hole, as described above. In a preferred embodiment of the invention, the augering steps are performed at a maximum torque of 30T. Further preferably, the lens overlap between adjacent holes of the first and second series of basis holes has a maximum value of 200mm. Further preferably, the lens overlap has a maximum value of 150mm. Although Fig. 4 shows example blocks of process 400, in some implementations, process 400 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in Fig. 4. Additionally, or alternatively, two or more of the blocks of process 400 may be performed in parallel. The method of this invention also has the following advantages:- The method allows the cost effective 'open hole' / CFA augering technique to be maintained without having to consider a cased augering system. Provided a maximum torque at 30Te which was sufficient to allow the auger to progress through the competent bedrock strata. Ensured the augering technique could be carried out using a piling rig which was of similar size / nature to that which would install the sheet piles. If a cased augering system was required than a much larger rig would be required as a result of the dual activities of installing a casing and progressing the auger. The new method effectively overcame the problems identified using current techniques for pre-augering prior to sheet pile installation and the residual problems when considering a sheet pile solution in Weak / Weathered Rock. No shoulders of un-augered material remained along the pile line during pile installation. The drilling torque of the rig was sufficient to auger into the Weak / Weathered Rock, without removal of the material has has been drilled, so that the hole contains material that was loosened during the drilling process. In summary, the new method provided a continuous trench of augered / loosened ground along the sheet pile line, without requiring concrete or other grout to be put in the augered regions to receive the sheet piling, thereby ensuring a sheet pile solution could be successfully installed on the project. In the foregoing specification, the invention has been described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes may be made therein without departing from the scope of the invention as set forth in the appended claims, and that the claims are not limited to the specific examples described above. Details have not been explained in any greater extent than that considered necessary, for the understanding and appreciation of the underlying concepts of the present invention and in order not to distract from the teachings of the present invention. The word ‘comprising’ does not exclude the presence of other elements or steps then those listed in a claim. Furthermore, the terms ‘a’ or ‘an,’ as used herein, are defined as one or more than one. Also, the use of introductory phrases such as ‘at least one’ in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles ‘a’ or ‘an’ limits any particular claim to embodiments of the invention containing only one such element. The same holds true for the use of definite articles. Unless stated otherwise, terms such as ‘first’ and ‘second’ are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements.

Claims

Claims A method for preaugering and preparing a pile line on a construction site, comprising the steps of defining a central line relating to wherein sheet piling is to be installed; auguring a first circular basis hole of a first series of basis holes, with a diameter of x mm at a first position, with the centre of the first circular basis hole positioned on the central line; wherein material in the first circular basis hole is loosened by augering but not removed from the first circular basis hole; auguring a second circular basis hole of the first series of basis holes with a diameter of x mm, with the centre of the second circular basis hole on the central line, where the separation, y, between the centre of the first and the second circular basis hole is given by 17 Xsys 13x mm; where the material in the second basis hole is loosened by the augering but not removed from the first circular basis hole: repeating the auguring step for the first series of basis holes (n-2) times, to produce a series of n circular basis holes, all with centres along the central line, where the separation between each successive basis hole of the first series is given by 13x sys1 : Xx mm; where the material in each successive basis hole is loosened by the augering but not removed from each successive basis hole; augering a first circular basis hole of a second series of basis holes with a diameter of x mm , where the first circular basis hole of the second series is located between the first and second holes of the first series of basis holes, with a centre on the central line, so that the circumference of the first circular basis hole of the second series of basis holes overlaps with the circumference of the first and second basis holes of the first series of basis holes to form a first lens overlap between the first hole of the first series of basis holes and the first hole of the second series of basis holes, and a second lens overlap between the first hole of the second series of basis holes and the second hole of the first series of basis holes ; where the material in the first circular basis hole of the second series of basis holes is loosened by the augering but not removed from the basis hole; repeating the auguring step for the second series of basis holes (n-1) times, to produce a second series of n circular basis holes, where the material in each basis hole of the second series of basis holes is loosened by the augering but not removed from the basis hole; where the nth circular basis hole of the second series is located between the nth and n+1th basis hole of the first series of basis holes, so that the circumference of the nth circular basis hole of the second series overlaps with the circumference of the nth and n+1th basis holes of the first series of basis holes, so that the basis holes of the first and second series of basis holes are arranged alternately, and they is a lens shaped overlap between every adjacent basis hole inserting sheet piling between the first basis hole of the first series of basis holes, and the first basis hole of the second series of basis holes, and repeating the sheet piling insertion, so that the sheet pile installation extends from the first hole of the first series of basis holes through all the holes in the first and second series of basis holes, where the sheet piling is inserted into the loosened material in each of the basis holes...

2. A method as claimed in claim 1 wherein the sheet piling to be inserted is Z shaped sheet piling.

3. A method as claimed in claim 1 or claim 2 wherein the central line is a substantially vertical line.

4. A method as claimed in any preceding claim wherein x is between 500mm-1200mm.

5. A method as claimed in any preceding claim wherein the preaugering is done into a rock substrate.

6. A method as claimed in claim 5 wherein the rock substrate is weathered sandstone with an SPT value between 300-600.

7. A method as claimed in any preceding claim wherein the augering steps are performed at a maximum torque of 30T.

8. A method as claimed in any preceding claim wherein the lens overlap between adjacent holes of the first and second series of basis holes has a maximum value of 200 mm.

9. A method as claimed in claim 6 wherein the lens overlap has a maximum value of 150mm.

10. A method as claimed in any preceding claim wherein n is as least 4. Amendments to the claims have been filed as follows: Claims A method for preaugering and preparing a pile line on a construction site, comprising the steps of defining a central line relating to wherein sheet piling is to be installed; auguring a first circular basis hole of a first series of basis holes, with a diameter of x mm at a first position, with the centre of the first circular basis hole positioned on the central line; wherein material in the first circular basis hole is loosened by augering but not removed from the first circular basis hole; auguring a second circular basis hole of the first series of basis holes with a diameter of x mm, with the centre of the second circular basis hole on the central line, where the separation, y, between the centre of the first and the second circular basis hole is given by 17 Xsys 13x mm; where the material in the second basis hole is loosened by the augering but not removed from the first circular basis hole; repeating the auguring step for the first series of basis holes (n-2) times, to produce a series of n circular basis holes, all with centres along the central line, where the separation between each successive basis hole of the first series is given by 13x sys1 : Xx mm; where the material in each successive basis hole is loosened by the augering but not removed from each successive basis hole; augering a first circular basis hole of a second series of basis holes with a diameter of x mm , where the first circular basis hole of the second series is located between the first and second holes of the first series of basis holes, with a centre on the central line, so that the circumference of the first circular basis hole of the second series of basis holes overlaps with the circumference of the first and second basis holes of the first series of basis holes to form a first lens overlap between the first hole of the first series of basis holes and the first hole of the second series of basis holes, and a second lens overlap between the first hole of the second series of basis holes and the second hole of the first series of basis holes ; where the material in the first circular basis hole of the second series of basis holes is loosened by the augering but not removed from the basis hole; repeating the auguring step for the second series of basis holes (n-1) times, to produce a second series of n circular basis holes, where the material in each basis hole of the second series of basis holes is loosened by the augering but not removed from the basis hole; where the nth circular basis hole of the second series is located between the nth and n+1th basis hole of the first series of basis holes, so that the circumference of the nth circular basis hole of the second series overlaps with the circumference of the nth and n+1th basis holes of the first series of basis holes, so that the basis holes of the first and second series of basis holes are arranged alternately, and there is a lens shaped overlap between every adjacent basis hole inserting sheet piling between the first basis hole of the first series of basis holes, and the first basis hole of the second series of basis holes, and repeating the sheet piling insertion, so that the sheet pile installation extends from the first hole of the first series of basis holes through all the holes in the first and second series of basis holes, where the sheet piling is inserted into the loosened material in each of the basis holes..

2. A method as claimed in claim 1 wherein the sheet piling to be inserted is Z shaped sheet piling.

3. A method as claimed in claim 1 or claim 2 wherein the central line is a substantially vertical line.

4. A method as claimed in any preceding claim wherein x is between 500mm-1200mm.

5. A method as claimed in any preceding claim wherein the preaugering is done into a rock substrate.

6. A method as claimed in claim 5 wherein the rock substrate is weathered sandstone with an SPT (standard penetration test) value between 300-600.

7. A method as claimed in any preceding claim wherein the augering steps are performed at a maximum torque of 30T (294200 Nm).

8. A method as claimed in any preceding claim wherein the lens overlap between adjacent holes of the first and second series of basis holes has a maximum value of 200 mm.

9. A method as claimed in claim 6 wherein the lens overlap has a maximum value of 150mm.

10. A method as claimed in any preceding claim wherein n is as least 4.

Images