BACKGROUND ART Sheet-piling has been used in the construction industry for over 200 years to support excavations, create seepage cut-offs, form quay walls and stabilise ground slopes. The sheet-piling can be used as a free standing structure or used in conjunction with tie-backs, ground anchors or props. Earth and groundwater loads are dispersed along and across the sheet-pile profile making flexural strength the main factor in the design of the sheet-pile profile.

Conventional sheet-piling consists of hot rolled steel sections (t > 7.5 mm thick) manufactured to unit profiles (U or Z) which are linked through interlocking joints to create a complete structural section. In recent years, a series of light sheetpile profiles have been developed from folded or cold rolled plate into lighter versions of the standard sheet-pile. Also pleated or corrugated sheet profiles have been used as light sheet-piles. The normal sheet-piles lie within a narrow range of simple profiles, usually being progressively developed form the original Frodringham (Z) and Larrsen (U) sheet-pile profiles.

Recently specific ranges of'wide'sheet-pile (w> 1000 mm) have been proposed in the prior-art literature. A large part of the'prior-art'has been created by the Inventors prior patents in which the profiles were catagorised by eight sets of dimensions, (d, t, f, i, f/d, ws/t, n, N) as defined in Figure 1. The various sheetpiles created within these profile dimensions were linked by interlocking joints made up of a variety of slide-able'female'/'male'elements along both edges of the sheetpiles.

The sheet-piles may also be fitted out with stiffeners in the form of folded plates, bars or rods across the sheet-pile section. Provision was made for the attachment of de- watering tubes on one side of the sheet-pile to drain-off groundwater at the sheet-pile line. The profiles and means proposed within this new Invention lie outside the profiles covered in the preceding patents and other'prior-art'.

STATEMENT OF INVENTION The present invention consists of a sheet-pile made up of a single (N= or <1) or dual (N = or < 2) profile out of steel, aluminum, fiber reinforced plastic or other form-able materials. The profile is made up of a stiffening means (0.5 = or < n = or < 2.0) (SP) fitted with joint means (JS) along each edge of the stiffening means-see Figures 2 and 3. The joint flange width (f/2) of the earlier'prior-art'is divided into two sizings (fi) & (fii) on alternating profiles (fi X fii). This creates sheet-piles with different profiles for single sheet-piles (N = or < 1) or dual sheet-piles (N = or < 2) with unequal profile. However dual sheet-piles (N = or < 2) may have equal profiles within the sheet-pile.

Dimensions specifying the profile of the stiffening means (SP) on the basis of the terminology in the preceding'prior-art', both profiles are defined by:- 150 mm = or < d < 700 mm t < 30 mm 0 < f < 1000 mm 0 < fi < 400 mm 0 = or < fii < fi 45° < i < 125° 0=or<f/d=or< 1.3 w/t > 40 0. 5 = or < n = or < 2. 0 N = &< 2. 0 where (d) is the depth of the profile, (t) is the thickness of the material forming the profile, (f, fi & fii) are the widths of the fanges, (i) is the inclination of the webs of the profile, n is the number of profiles of a specific set of dimensions within the sheet-pile width (w) and N is the total number profiles within this sheet-pile width (w)-see Figure 2. In the case of N = 0.5 a'true'Z profile is created-see Figure 2G. While the web panel connecting the flange panels of the stiffening means (SP) is usually planar, it may be broken into two or more subpanels of different inclinations (ii, i2 etc) within the depth (di & dii) and web inclination range (I) stated above to create sub-variant profiles-see Figures 2H & 21.

The thickness of the material forming the profile (t) is constant across the profile. However the thickness (t) may vary along the sheet-pile. Also the thickness (t) of the basic profile can be upgraded by the provision of supplementary flange plates on the profile or by overlapping profiles (n = or < 1.0)-see Figure 3. Extra flange and web plates may be employed to cover local bearing loads, delay onset of panel buckling and flexure and/or web shears. The deeper profile are particularly suited to the use of fiber reinforced plastic materials.

This profile is incomplete as a sheet-pile until inclusion of the joint strips (JS) either extends the ends of the stiffening panel (SP) or are incorporated into the edge of the stiffening panel to provide a slide-able interlocking joints. The joint strips (JS) complete the various sheet-pile profiles forming this Invention,-see Figure 3. The overall profile forms a complete structural element equal in stiffness to the final insitu profile. Thus it represents an improvement over conventional U and Z sheet-piles in which the profile forms only half of sheet-pile's final profile with a much reduced stiffness and strength. The joint strips on both sides of a particular sheet-pile can consist of either Type 1 and/or Type 2 slide-able joints-see Figures 4A to 4E.

However it is preferable that only Type 1 or Type 2 joints are provided on a particular profile. This differs from normal sheet-piles on which a'male'and'female'joints are used on the opposite sides of a single sheet-pile. The Type 1 or Type 2 slide-able joints may be fitted to either of the two profiles with the (fi) or (fii) edge fanges. The dimensions of the profiles (n) within a sheet-pile or of alternate sheet-piles piles with the Type 1 and Type 2 joints can be the same or differ in all aspects (d, t, f, fi, fii, i, f/d, w/t, n, N). However it is preferable to maintain an equal, and symmetrical profile in each sheet-pile and similar profiles between sheet-piles-see Figure 3. However some profiles allow the Type 1 and 2 joints to be similar or identical with reversal or overlap forming the interlock-see Figure 3C and 3D. In one case, the Type 2 joint forms a means of overlapping the two Type 1 joints-see Figure 3E.

The sheet-piles fitted with one joint type (Type 1) are driven first at every second locations as'soldier'piles along the sheet-pile alignment. Thence the sheet- piles fitted with other joint type (Type 2) are driven as'infill'piles between the'soldier' sheet-piles. A reverse driving sequence in which the sheet-piles with the Type 2 joints are driven first and thence sheet-piles with the Type 1 joints can be adopted with the joint means formed by hollow sections for the Type 2 joints. While the Type

1 and Type 2 joints can be in any form, the preferable forms used in this Invention are made up of:- * A'clasp'joint formed to allow the joint means to provided for an sharp angular change at the edge of the sheet-piles-see Figure 4A. This includes conventional joint means being added to a bent plate on the edge of the stiffening profile-see Figure 4B * A triangular or polygonal Type 1 joint of formed, moulded or fabricated to dimensions in the range of:- <BR> <BR> 75=or<d, =or<300mm<BR> 75=or<d2=or<250mm - 30° < or = ß < or = 30° D = orD = or 45°<BR> s = or < 25 mm t = or < 20 mm and a complementary Type 2 joint made up of either a smaller triangular joint or a out-turned plate, both having dimensions to fit loosely into the Type 1 joint-see Figures 4C-1/2. In the Type 2 plate joint, the dimensions are in the range of:- 25 = or < d3 = or < 150 mm<BR> 70°<or=a<or=150° t = or < 20 mm * An'encircling'Type 1 joint with a slot oriented to match the incoming Type 2 joint on the alter- nate sheetpile-see Figure 4 C. The'encircling' member forming the Type 1 joint may be a pipe, square or polygonal sections, within the following

dimensions:- <BR> 50 = or < d4= or < 250<BR> i-30°=or< B=or<i+30°<BR> 0 = or < â =s i + 20°<BR> t = &< 30 mm within which a complementary shaped Type 2 means will loosely fit-see Figure 4 C.

* A triangular Type 1 joint with a slot at the center of one face and oriented to match the inclination of the incoming web of the Type 2 joint of the alternate sheetpile-see Figure 4 D The encircling means forming the Type 1 joint shall be within the following dimensions:- 50 = or < d4= or < 250 75° -1 = or < ß = or < i + 110° 60° = or, < # = or < 150°<BR> t=or<30mm within which a complementary shaped Type 2 means or flat T plate will loosely fit-see Figure 4E.

* A'overlap'joint formed by the re-entrant corner in the profile being fitted with an upstanding plate as per the Type 2-see Figure 4B-1/2 to form an interlocking'wedge' -see Figure 3 C and 3E. However the re-entrant corners can become a means of partially inter-locking the sheet- piles.

These dimensions are selected to offset the wider ( flange to maintain the profiles centroid or neutral axis at or close to the central third of the web panels. The

joint strips (JS-Type 1 & 2) may be either formed into the edge of the stiffener profile (SP) or connected onto it, preferably by welding.

The final profile forms a structural section acting as two incline (i), opposing plates diaphragm plates connected at the flange imparting a resistance to flexure and shear effects in the transverse and longitudinal axis of the sheet-pile. This stiffness is much higher than in the normal sheet-pile profile which individually form an incomplete section. This'plate'diaphgram system allows the sheet-pile to be driven accurately by large static or dynamic forces. However the joint strip offers little stiffness to transverse forces unless stiffened by'stiffeners'across the profile as outlined in the preceding patent by the Inventor. These stiffeners are required above to ground to remove joint misalignments in the sheet-pile and maintain the joint aligned along the sheet-piles axis matching the imprint in the ground created by the tip of the sheet-pile. The stiffeners are removed on entry into the ground after which the alignment has to be set by the longitudinal stiffness of the joint means (Iyy> 300 cm4).

The looser fit of these joint reduces the joint friction and tolerance in the joint.

Also the internal surfaces to be coated and the coatings preserved during driving.

The coatings include zinc galvanizing and thicker (> 300um) tar epoxy coatings etc.

The joints of the slotted Type 1 or hollow Type 2 joints can be pre-drill through the joint to facilitate penetration into'hard', cemented or dense ground. The hollow Type 2 joints can be fitted out to act as jetting tubes to facilitate penetration into the Type 1 joint and/or dense strata. The hollow Type 2 joints can be used to grout up the joint assembly to seal the slide-able joints against the through flow of groundwater. In the case of non-hollow Type 2 joints, sealing can be achieved by prior filling of the Type 1 joint with sealant, injection of grout or sealants after driving through an enclosed void in the re-entrant corner of the joint means. The sealant may be cement/bentonite grout, polystyrene, solid foam etc. The slotted Type 1 and hollow Type 2 joints can be surveyed using an inclinometer apparatus prior to driving of the alternate'infill'sheet-pile or through the hollow Type 2 joints on completion of the sheet-piling but prior to excavation. These ancillary functions may determine the sizing of the sheet-pile joints.

The sheet-pile profiles can be fitted out with subsoil drains down selected segments of the sheet-pile with the installation of a'cover'plate, angle plate or'half' pipe to form a'void'behind the sheet-pile wall-see Figure 5. Entry of ground water into this drain occurs either through discontinuities in the sheet-pile/cover plate joint connection and/or slots or holes cut into the'cover'plate. The'void'can be filled with a filter material and/or drain strip to forestall soil erosion and/or entry of fines into the drain. Drainage of the enclosed void occurs through small outlet holes cut through sheet-pile wall at any level needed to generally or selectively drain the groundwater level-see Figure 5. The subsoil drains can also be used in reverse to recharge groundwater levels behind the sheet-piling that would otherwise be drawn down by the excavation.