Abstract:
A landfill site is lined by attaching an impermeable line ( 90 ) to a support structure for the purpose of containing waste material and preventing substances from draining or being leached from the waste into the subsoil. The support structure comprises a plurality of substantially rectangular panels ( 10 ) with rolled edges ( 14, 15, 16, 17 ) and their corners removed. The panels are supported and located adjacent to the wall of the landfill site in a planar array by a plurality of bolts ( 30 ) which are connected to the wall of the landfill site and pass through the opening ( 32 ) constituted by the absent comers of the panels. Adjacent pairs of rolled edges of adjacent panels are engaged by respective elongate C-section linking strips ( 45 ) which connect the panels together in a manner which permits at least limited relative pivotal movement

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to the lining of landfill sites for receiving waste, and more particularly, but not exclusively, to provision of a support structure for a flexible impervious lining intended to contain the waste material and to prevent elements of that material from draining into or being leeched from the waste into the subsoil and water table. 
     Spent or disused quarries and other excavations are commonly used for tipping domestic and other waste. The sheer variety of material contained in such waste virtually ensures the presence of potentially environmentally damaging materials. There has for some years been increasing concern to prevent such potentially damaging materials either from draining from the tipped waste into the subsoil and further, or being leeched from the waste by rainfall to the same effect. Quarry and other excavation sites may or may not be in substantially impervious materials, but the tendency now of authorities responsible for environmental protection is not to rely on that and, whether the proposed landfill site is in impervious material or not, to require provision of an impervious lining at least along the base and up the side walls of tipped sites, and in some cases for that lining to be completed by a sealed impervious cap so as totally to enclose the tipped material. 
     A variety of methods for lining a tipping site have been proposed. It is all but essential now for such lining to comprise a continuous flexible impervious lining produced by welding or otherwise affixing together discrete sheets of the lining material. Given the irregularity of the walls and base of most landfill sites, it is generally not feasible simply to lay a flexible sheet or membrane in place and various methods have been proposed for provision of a stable substrate eg constructed out from the walls of a disused quarry, against which the flexible membrane can sit and be supported without concern over breach of the flexible material by interaction with it by the quarry face and/or the tipped waste. There are such methods which involve essentially building a fresh wall to the quarry for example using gabions containing rocks or the like, or by use of a rigid metal framework to which are attached sheets of expanded metal. The former has a number of disadvantages not least of which that it involves substantial incursion into the tipping volume available. The latter involves initial construction of an extensive and robust framework around the quarry wall and moreover can suffer problems with cutting of the flexible liner sheet by the proud edges of the slits of the expanded metal sheet. 
     It is an object of the present invention to provide a simpler, more effective and cheaper support construction for a flexible impervious lining of a landfill or tipping site such as a quarry. 
     It will be appreciated in this specification that references to quarries are not, unless the context is to the contrary, intended to be restricted to quarry sites themselves and can refer equally to other excavated tipping sites or even naturally occurring tipping sites. 
     SUMMARY OF THE INVENTION 
     According to the present invention a support structure for lining a landfill site comprises: 
     (i) a plurality of substantially rigid panels with rolled edges; 
     (ii) means to locate and support the plurality of panels side by side in a substantially planar array with the rolled edges of adjacent panels in close juxtaposition; and 
     (iii) substantially C-section elongate linking strips arranged to engage around the adjacent rolled edges c- two adjacent panels and thereby to connect the panels together. 
     The term “rolled ” when used herein in relation to an edge of the panels is used to define a edge having a channel along it, whether formed by rolling or folding or bending the panel edge over on itself, by affixing arcuate or chined flange(s) thereon or by any other suitable expedient. 
     The resulting channel may be formed eg by “rolling” the edge of the sheet through any appropriate angle. A 180 degree “roll” may suffice although a “roll” through a greater angle may provide greater location with the said elongate linking strips. If the channel is truly rolled then the edges of the panels are likely to be of arcuate shape. In practice, the channels are more likely to be formed by the processes commonly referred to as bending or folding and in this case it is convenient for the edges of the panels to have two or three substantially right angle bends. However, a lesser angle is also possible but the bend or rolling should be through at least 90° and in practice through at least about 120°. 
     The C-section of the elongate linking strips may likewise be formed to have two inwardly opposing facing channels along opposite edges formed by rolling or folding the edges of an elongate metallic strip over on themselves, by affixing arcuate or chined flange(s) thereon or by any other suitable expedient. In this event the channels in the linking strips will accommodate respective edges of adjacent panels which are thus connected together in the manner of a hinge, which permits relative rotation of the associated panels and thus ready adaption of the support structure to an uneven or undulating surface of the quarry wall against which the support structure is to be constructed. Additional strength is thus imparted to the structure. 
     The combination of the the rolled edges of the panels and of the linking strips provides an marked degree of stiffening and reinforcement to the panel array, as well as a means of articulated connection of adjacent panels. If flexibility of the panels is desired, e.g. to permit adaptation to an unusually uneven quarry wall, at least certain of the rolled edges may have a gap or discontinuity in them. 
     The panels are preferably configured to leave openings between adjacent panels, when they are assembled, for the location and support means. The panels are preferably rectangular with each corner removed, whereby substantially quadrilateral openings are defined between adjacent panels, when the panels are assembled, for the location and support means. Each panel may be provided with means to attach a flexible impermeable liner thereto. 
     The invention also embraces a support structure of the type referred to above in situ in a landfill site in which the panels are located and supported side by side in a substantially planar array by the locating and support means and adjacent pairs of rolled edges of adjacent panels are connected together by respective linking strips and in which the locating and support means are affixed to the wall of a landfill site or to a substantially vertical framework extending from the base of the landfill site. The location and support means preferably comprises rods or bolts protruding from the wall of the landfill site or from the framework. The rods or bolts preferably extend through and are affixed to the panels at the periphery of the openings defined between them. 
     In the preferred embodiment each rod or bolt carries an abutment, e.g. in the form of a plate, which is engaged by one side of the panels defining the opening through which the rod or bolt extends, retaining means, e.g. in the form of a retaining plate, engaging the other side of the said panels and a fastener holding the retaining plate in position, e.g. a nut screw threaded onto the bolt. 
     The invention also embraces a lining for a landfill site comprising a support structure as referred to above and a flexible impermeable liner supported thereby. 
     The invention also embraces a method of constructing a support structure for a lining for a landfill site comprising: 
     (i) affixing location and support means to the wall of the landfill site or to a substantially vertical framework extending from the base of the landfill site, 
     (ii) aligning and affixing panels to and between the location and support means in a substantially planar array, the panels each having rolled edges, each rolled edge being located adjacent a rolled edge of an adjacent panel in the array, and 
     (iii) connecting adjacent rolled edges of adjacent panels by engaging substantially C-section elongate linking strips around them. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may be put into practice in various ways, some of which will now be described, by way of example, with reference to the accompanying diagrammatic drawings in which: 
     FIG. 1 is a plan view of a panel for use in constructing the support framework for a landfill site lining according to one aspect of the present invention. 
     FIG. 2 is a scrap sectional view of a corner of the panel of FIG. 1 in the direction of the arrows I—I. 
     FIG. 3 is a view of an assembly of panels as shown in FIG. 1 located against eg a quarry wall (not shown); FIG. 3A shows a detail variation of a clamping plate in FIG.  3 . 
     FIG. 4 is a scrap section along the line II—II of FIG. 3 showing the manner in which the panels are connected. 
     FIG. 5 is a further scrap sectional view in the direction of the arrows III—III of FIG. 3 through a connection of the panel array to eg a quarry wall behind. 
     FIG. 6 is a sectional view of a joint between two adjacent panels showing one form of means to affix a flexible impervious lining sheet thereto. 
     FIG. 7 is a sectional view of a further form of clamp used with the arrangement of FIG. 6 to affix a plurality of flexible impervious lining sheets to the panels. 
     FIGS. 8A &amp; B are scrap sections similar to FIG. 6 but of a further embodiment 
     FIG. 9 is a scrap section similar to FIG. 6 but of a still further embodiment 
     FIG. 10 shows a further embodiment of a liner support and liner 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings, FIG. 1 shows a substantially rectangular panel  10  of mild steel sheet, galvanised or otherwise protected against corrosion. It is approximately 3 metres by 1.5 metres, though may be larger or smaller, e.g. 1 metre by 0.5 metre, and has its four corners  12  removed. Each of the edges ( 14  to  17 ) of the panel  10  is rolled as shown in section in FIG. 2, the rolled edges providing stiffening and reinforcement to the panel  10  and, as will be described below, a means of connection of adjacent panels  10  when disposed in a planar array against eg a quarry wall. 
     As shown in FIG. 2, the edge  14 , and indeed the other three edges are rolled or otherwise bent through substantially 180°. However, as shown by the dotted portion  14 ′, the edge may be rolled through a larger angle of e.g. 270° which will result in a greater degree of location with linking strips  45  (see below). In alternative embodiments each edge of the panel may be formed into a channel of equivalent effect eg by bending or folding the panel edge over on itself, by affixing arcuate or chined flange(s) thereon or by any other suitable expedient. 
     The panel  10  is provided with impressed corrugations  20  to provide further reinforcement. The corrugations  20  in this embodiment are substantially diagonal but can be of any structurally sound and effective disposition. 
     FIG. 3 shows an array of panels  10  located with their edges adjacent to one another. In this view the array would normally be vertical or substantially vertically disposed up against the wall of the quarry or like landfill site. The wall of the landfill site is first prepared by affixing to it a pattern of mounting rods or bolts  30  each of which protrudes from the wall (not shown in FIG. 3 —but see FIG. 5) to a degree sufficient to pass through the intended plane of location of the array of panels  10  at that point. 
     The absence of corners  12  from each panel  10  creates a substantially square recess or opening  32  at each point where four panels  10  meet. The panels  10  are arranged so that a rod or bolt  30  affixed to eg the quarry face protrudes through each recess  32 . Means to locate and optionally clamp the array of panels  10  to each rod or bolt  30  are provided. Each rod or bolt  30  is provided with a rear locating washer or plate  38  affixed eg by welding onto the rod or on a thread to an appropriate position behind the plane in which the panel array is to be located. The rear locating washer may be of a shape and area substantially exceeding that of the recess  32  to provide a stable base on which the panels  10  may sit. A round washer  34  of a diameter sufficient to extend over the edges of each removed corner  12  is used to clamp the four panels to the plate  38 . Alternatively a square washer  36  of similar dimensions to the recess  32  may be used located at roughly 45° to the recess  32  so that the corners of the square washer  36  overlay the corners  12  of the adjacent panels  10 . That arrangement is shown in section at FIG.  5 . 
     In a further form (see also FIG. 3A) a larger plate  37  may be provided to be located over the rod or bolt  30  to clamp the array of panels  10 . The plate  37  may have pressed radial channels  39  to receive the edges of the panels proud of the surface of the panels  10  to allow the plate  37  to sit flush with the surfaces of the panels  10 . 
     The panel array is then clamped between the washers or plates  38  and  34 , 36  or  37  for example by nut  40  threaded on to the bolt  30 . 
     If required for further support of the panel, elements (not shown) may be affixed to the quarry face with intermediate rods or bolts  30  so that any excess pressure on the panels  10  from tipped waste will press the panels  10  onto the support elements rather than causing them to buckle or sag. The support elements may for example be rods with flanges affixed thereto parallel to the plane of the intended array of panels  10 . This manner of further support, if provided, will optimally be located behind each panel  10  at approximately the intersection of the diagonals of the panel  10 . 
     As already indicated the rolled edges  14  to  17  of each panel serve not only to reinforce the panel but also to provide a means for connecting together an array of panels as shown in FIG.  3 . The section shown at FIG. 4 shows two adjacent panels  10  against a quarry face  50 . The upper edge  14  of the lower panel  10  is adjacent to or abuts the lower edge  16  of the upper panel  10  and the whole array is held in place for example as described in relation to FIGS. 3 and 5 above. 
     A linking strip  45  is provided having a substantially C-shaped section. It may be made of the same mild steel, galvanised or otherwise protected, as the panels  10 . A suitable length of the linking strip  45  is provided, either as a single strip or a number of shorter strips, preferably over the whole length of the rolled edges  14 / 16  of the adjacent panels  10 , and is slid in place with the rolled edges  14  and  16  of the panels  10  being received in the opposing channels  46  and  47  of the linking strip  45  thereby locking the adjacent panels  10  to one another. Corresponding strips  45  would be provided at the vertical edges  15  and  17  of each panels  10  and as the array of panels  10  is built up using the bolt  30 , washers or plates  38  and  34 ,  36  or  37  and linking strip  45  arrangement a rigid support structure is produced affixed to the quarry wall  50 . 
     In areas where the quarry wall is not capable of supporting bolts  30  or the like, or where an array of support panels  10  is required to be free standing for example to section off an area of an excavation site, then a freestanding framework (not shown) may be provided for attachment of the bolts  30  or the like, the free-standing framework either being built up from the quarry floor or being affixed to any stable area of the quarry wall  50  adjacent to the point or points at which bolts  30  or the like are required to be located to support the array of panels  10 . 
     In a further embodiment of the invention the array of panels  10  may be located such that the lower run of panels  10  is not located vertically but is located at an angle of say 45° to the quarry base to provide in effect a chamfer in section and thereby avoid the need for the flexible impermeable membrane sheet (see below) to have to bridge right angled corners. In that case the upper bolts  30  to locate the lower level of panels  10  would be located rather closer to the base of the quarry. A further line of bolts  30  or the like may also be required to be located in the quarry base approximately 0.75 metres from the plane of the array of panels  10  to affix the bottom panel at the desired eg 45° angle. 
     The intention of the constructed array of panels  10  is to support a conventional flexible impervious synthetic liner. For obvious reasons the lining material will be provided in discreet sheets or areas along the support array of panels  10  and adjacent, and preferably overlapping, sheets of the liner material will be welded or otherwise affixed to one another in the conventional manner. 
     Once the support structure provided by the array of panel  10  is in place either against the quarry or the like wall or supported by a free standing framework, a liner of suitable impervious flexible sheeting needs to be affixed to the array of panels  10 . In this embodiment each of the panels  10  is provided near an edge  16  with fixing points  60 / 61 , for example keyhole arrangements. As shown in FIG. 6, a channel member  65  is provided in a length corresponding to the horizontal dimension of panel  10 , as shown in FIG. 1, and the channel member  65  has affixed along its length a plate  67  which protrudes above the channel member  65  at  66  and below channel member  65  at  68 . The protrusion  66  of the plate  67  is provided with means to attach the channel and plate assembly  65 / 67  to a panel  10  by use eg of a key arrangement  70  which engages with a corresponding fixing point  60 / 61  on the panel  10 . The protrusion  68  beneath the channel member  65  extends down into the rolled lower edge  16  of the panel  10 . The arrangement thereby produces a channel running adjacent to the bottom rolled edge  16  firmly affixed to the panel  10 . The channel member  65  itself has a rolled front edge  72  for reasons which will become apparent below. 
     Next there is provided a double channel clamping member  75  made up of two C-section linear channels  77  and  79  which can be bolted or otherwise affixed together by bolts or other fixings  80 . It will be seen that the combination  75  of channel members  77  and  79  is arranged to fit stably into the channel member  65 . In FIG.6, a flexible impervious membrane lining material  90  is fed between the channels  77  and  79  and the channel members  77  and  79  are clamped on to the liner  90  to secure the liner  90  between them. The clamp  75  is then dropped into the channel  65  and the membrane  90  arranged so that it lies along the rolled edge  72  of the channel member  65  and drops down over the face of the panel  10  or panels  10  below depending on the length of the membrane sheet  90 . The next arrangement of a channel member  65  will be affixed to a lower row of panels  10  above the foot (not shown) of the membrane sheet  90  and the arrangement repeated. The lower end of the membrane sheet (equivalent to  90 ′ in FIG. 6) can therefore be affixed (eg welded) where it overlaps with the equivalent but lower sheet  90  and thereby a waterproof lining to the landfill site can be built up. 
     FIG. 7 shows a modified version of the clamp  75  and membrane  90  arrangement to fit in channel  65  where it is felt that a compound lining may be required comprising a number of liners or membranes selected with their properties directed to waterproofing, scuff resistance, physical integrity or whatever. Three different liners or membranes  90 ,  91  and  92  are shown. Liner  90  is the flexible impervious liner as above. A protective membrane  91  is provided on the quarry side of membrane  90 , with a further protective membrane  92  being provided on the waste side of membrane  90 . The protective membranes  91  and  92  may be of “Gedtex” or similar protective material. With this multi-layer construction it will be apparent that the membrane  90 ′ from the arrangement above that shown in FIG. 7 will in fact not contact membrane  90  for welding —there will be two layers of protective membrane  91 / 92  between them. To address this a further membrane  93  made of the same liner material as membrane  90  overlays membrane  92  to a depth sufficient only to provide a point of welding contact with membrane  90 ′. The four membranes  90 / 91 / 92 / 93  are clamped between the channel members  77  and  79  and passed in different routes around those channel members so that they can be overlaid in layers over the rolled edge  72  on the front of the clamp member  65 . 
     With a single layer arrangement such as that shown in FIG. 6 the vertical, lateral, edges of the membranes  90  may overlap for welding together or a supplemental strip of suitable liner material may be welded in place to link adjacent drops of liner membranes  90 . When a multi-layer liner arrangement, eg as shown in FIG. 7, is used essentially the same welding operation will be required, but for further protection she waste-side protective layers  93  of adjacent drops may be joined by a further strip of similar material by adhesion, clamping or “Velcro” to reduce the risk of damage to the liner sheet  90  between the adjacent drops of protective sheet  93 . 
     The various forms of the invention described above all have the “rolled” edges of the panels  10  facing the intended waste-side of the panels  10  in use. This facilitates assembly of the support structure but means that the liner will overlie the linking strips  45 . This may well not constitute a problem, depending on the composition and thickness of the liner, because the linking strips present a relatively smooth surface and are thus unlikely to puncture the liner. However, if this is thought to be a potential problem, the problem may be eliminated by filling the rectangular spaces defined by the lining strips with lightweight panels, e.g. of polystyrene whose thickness is such that their surface opposed to the liner is substantially flush with that of the linking strips. However, FIGS. 8 A &amp; B show an alternative arrangement of the panels  10  with their rolled edges  14  on the quarry-side of a panel array, in each case with a modified form of channel member  65 A and  65 B, and this of course also eliminates the potential problem referred to above in that this form of construction presents a smooth face to the inside (waste-side) of the quarry. In each case a linking strip  45  (not shown here) of suitable construction will be affixed over the edges of the adjacent panels  10  at the rear of the array. 
     FIG. 9 shows a further modified form of channel member  65 C using an arrangement of panels  10  having their “rolled” edges facing the intended waste-side of the quarry. It will be appreciated that either the linking strip  45  (not shown) or the modified channel member  65 C must be interrupted along the length of a panel  10  for this to work. 
     The channel member  65  and plate  66 , and the channel members  77  and  79  making up the clamp member  75  may be made in the same materials as the panels  10  and linking strips  45 , again suitably protected against corrosion. 
     If required, a stabilising or cover strip may be bolted or welded over the channel member  65  (or  65 A, B) to ensure that the clamping member  75  and its membrane sheet load remain in place and protected. 
     FIG. 10 shows a modified arrangement of liner. support and liner which uses a channel member  86  of similar construction to channel member  65  of eg FIG. 6, but with its front edge  73  rolled inward rather than outward as at  72 . The clamp member  85  differs from previously described clamp member  75  in that its central clamping walls are at an angle of about  75  degrees to the “horizontal” plane as shown in the drawing. The outer element  89  of the clamping member  85  has its upper edge  97  at a position such that, with the clamping member  85  in place in the channel member  86  as shown, the upper edge  97  snap-fits under the inward rolled front edge  73  to lock the clamping member in place. 
     The liner  90 , or multi-layer lining arrangement used in this embodiment, may take any appropriate form. The arrangement shown in FIG. 9 has a protective membrane  91  on the quarry-side of a flexible impervious liner  90 . A further membrane  100  of protective material is suspended temporarily from a fixing at  102  at the top of the panel  10  supporting the clamping member  85  and its membranes  90 / 91 . As the infill of waste (or a reinforcing wall of gabions if required) rises, the lower reaches of the membrane  100  will be clamped in place against the liner membrane  90 , its upper reaches being overlaid in turn by a next membrane  100 ′ (not shown). This may involve part of the membrane  100  or its support at  102  being discarded once the waste etc reaches a certain level. 
     It will be appreciated that the support structure is unlikely to extend truly vertically and in practice it is likely to extend somewhat rearwardly. This is not of itself a problem but does means that where e.g. the rear and side walls meet there is likely to be an upwardly diverging gap. This can be readily accommodated by using linking strips of upwardly increasing or decreasing width or inserting panels of upwardly increasing or decreasing width at that point or by covering the gap by galvanised plates affixed by welding, rivetting or otherwise.