Lining of landfill sites

Details Lining of landfill sites Lining of landfill sites

1999-03-01

2001-06-05

Lillis, Eileen D. (Department: 3673)

Hydraulic and earth engineering

Subterranean waste disposal, containment, or treatment

With treatment of waste

C405S258100

Reexamination Certificate

active

06241423

ABSTRACT:

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

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