WALL LINING STRUCTURE

The present invention relates to a wall lining structure and more particularly, but not exclusively, to a wall lining suitable for lining a wall of a landfill site or the like, such as a disused quarry.

A common problem in the construction industry is that a wall or surface of a containment structure does not have the characteristics of smoothness, durability or stability that are required in order for the structure to perform its intended function satisfactorily. For example, in the construction of landfill sites, a site must be lined with a liner having low permeability to fluids prior to use of the site, so as to prevent precipitation and ground fluid, such as water or air, from entering the site and to prevent fluid leachate, such as waste liquids and gases, from leaving the site.

A similar problem is encountered in the construction of reservoirs, in that a natural or man-made geological formation within which a reservoir is to reside is not always naturally impermeable to water, or may be susceptible to erosion by water, and must therefore be lined before the reservoir can be filled. Providing reliable and durable lining for walls is therefore an important problem.

In the case of landfill sites in particular, the problem of lining walls is exacerbated by the tendency of waste to settle over time, which causes solid waste adjacent the lining to drag against the lining as the waste moves, damaging and potentially breaching the lining. This makes the requirements for wall linings for landfill sites higher in terms of durability, integrity, stability and reliability.

A particular problem related to lining landfill or reservoir sites is that the lining must cover the steep walls of such sites. Previous attempts to line steep walls in landfill sites have included laying bunds of clay against the walls. However, clay generally cannot be laid to a gradient of greater than approximately 25° to the horizontal as clay is not sufficiently self-supporting. At a gradient of greater than

around 25° the clay would tend to become unstable and would therefore be unsafe and unreliable. Where clay is to be used as the hydraulic barrier material for a landfill lining system, it is generally laid as one or more layers of 500 to 1,000 mm thickness against a mineral bund formed from natural soils. The upper slope of the bund and the clay lining material are generally constrained to a maximum inclination in the order of 25° from the horizontal. The need to construct the natural soil bund and clay liner at these relatively modest inclinations has cost impacts in terms of provision of the natural soil bunds and clay liner, also the space lost within the landfill void space which could potentially generate income from receipt of waste materials.

Another approach to lining steep walls in landfill sites has been to use a geomembrane, constructed from for example, thin sheets of a polyolefin material, such as high-density polyethylene (HDPE). The geomembrane is suspended from the top of the wall and laid out to cover the wall. Covering walls, particularly steep walls, with a geomembrane does not incur the costs of lost void space and materials that are incurred by a clay lining. However geomembranes, such as those formed from HDPE, are not as resilient to damage as a clay bund, and so geomembrane liners suffer from problems relating to reliability and durability.

It is an object of the present invention to obviate or mitigate one or more of the problems with existing wall lining structures outlined above.

The present invention relates to a structure to line a wall comprising a bituminous layer provided with a sufficient level of reinforcement to secure the bituminous layer to the wall.

According to a first aspect of the present invention there is provided a wall lining structure for lining a wall of a landfill site or the like, the wall lining structure comprising a buffer layer to be located nearest to the wall, a first layer to be located adjacent to the buffer layer and a second layer to be located adjacent to the first

layer such that the first layer is located in between the buffer layer and the second layer and that the wall lining structure has an outer surface remote from the wall which defines an angle in the range of around 45° to 90° to horizontal, said first layer comprising a bituminous material and said second layer comprises an aggregate and a binder, wherein the second layer possesses an air voids content of up to around 20 %.

According to a second aspect of the present invention there is provided a wall lining structure for lining a wall of a landfill site or the like, the wall lining structure comprising a first layer comprising a bituminous material and at least one securing member arranged, in use, to secure the first layer to the wall.

The wall lining structure of the present invention provides significant advantages, particularly over existing clay and geo-membrane based lining structures, in that the structure of the present invention can be used to line significantly steeper walls than clay and the bituminous layer is more resistant to damage than most common geo-membranes.

According to a third aspect of the present invention there is provided a method of lining a wall of a landfill site or the like comprising: laying a first lift comprising a buffer layer to be located nearest to the wall, a first layer comprising a bituminous material to be located adjacent to the buffer layer and a second layer comprising an aggregate and a binder to be located adjacent to the first layer such that the first layer is located in between the buffer layer and the second layer and that the wall lining structure has an outer surface remote from the wall which defines an angle in the range of around 45° to 90° to horizontal, wherein the first layer and the or each other layer are laid simultaneously.

According to a fourth aspect of the present invention there is provided a method of lining a wall of a landfill site or the like comprising: laying a first lift comprising a buffer layer to be located nearest to the wall, a first layer comprising a bituminous

material to be located adjacent to the buffer layer and a second layer comprising an aggregate and a binder to be located adjacent to the first layer such that the first layer is located in between the buffer layer and the second layer and that the wall lining structure has an outer surface remote from the wall which defines an angle in the range of around 45° to 90° to horizontal the method further comprising: heating an upper surface of the first layer in the first lift; providing a second lift on the first lift so that the first layer of the second lift contacts the heated surface of the first layer of the first lift.

According to a fifth aspect of the present invention there is provided a method of lining a wall of a landfill site or the like comprising: laying a first lift including a first layer comprised of bituminous material; and securing the first layer to the wall using at least one securing member.

With regard to the methods forming the third, fourth and fifth aspects of the present invention it is preferred that the bituminous material is heated prior to being laid.

With regard to the fifth aspect of the invention it is preferred that the first lift further comprises a second layer adjacent the first layer, said second layer, when laid, being on a side of the first layer that is remote from the wall.

The methods according to the third, fourth and fifth aspects of the invention may further comprise laying said second layer on a fixation portion of a facing member, and locating a retaining portion of said facing member against the surface of the wall lining remote from the wall.

The first lift, and any subsequent lifts, may further comprise a third layer adjacent the second layer, said third layer, when laid, being on the side of the second layer that is remote from the wall. When a third layer is provided, it is preferred that the third layer, rather than the second layer, is laid on a fixation portion of a facing

member, and a retaining portion of said facing member is located against the surface of the wall lining remote from the wall.

With regard to the fourth and fifth aspects the first layer and the or each other (i.e. second and/or third) layer may be laid simultaneously.

The methods according to any of the above defined aspects may further comprise compacting the first lift and any subsequent lifts in any appropriate manner.

It is preferred that the method according to the third and/or fifth aspects of the present invention comprises heating an upper surface of the first layer in the first lift; and providing a second lift on the first lift so that the first layer of the second lift contacts the heated surface of the first layer of the first lift.

Concerning the fifth aspect of the invention it is preferred that the first lift further comprises a buffer layer provided between the first layer and the wall. Preferably the first and any subsequent lifts are arranged to form a waste-side surface (i.e. a surface remote from the wall being lined) which defines an angle of around 45° to 90° to horizontal, more preferably around 55° to 80° and most preferably around 70° to horizontal.

Concerning the first and second aspects of the present invention it is preferred that the outer surface of the wall lining facing away from the wall and into the space for receipt of waste defines an angle in the range of around 45° to 90° to horizontal, more preferably around 55° to 80° and most preferably around 70° to horizontal. The methods forming the third, fourth and/or fifth aspects may be employed to provide such arrangements. In contrast, existing methods for lining walls, such as clay bunds, cannot achieve such gradients. Where the outer surface of the wall lining is inclined to the vertical, i.e. defines an angle of less than 90° to horizontal, this inclination may be achieved in any convenient manner. For example, the lining may be constructed by laying any appropriate number of lifts and then finishing the

outer surface such that it defines the appropriate angle to horizontal, e.g. by removing greater amounts of material from successively higher lifts as necessary. More preferably, the desired inclination of the outer surface may be achieved by forming a first lift and then forming a second lift closer to the wall by a suitable distance to define a 'step' at the outer surface between the first and second lifts. Successively higher lifts can then be further stepped inwards (i.e. towards the wall) to provide the outer surface of the lining with the desired overall inclination.

In cases where the wall which is being lined defines an angle of between 45° and 90° to horizontal, a wall lining according to the present invention would be capable of lining the wall without the need to make the angle shallower, as is the case with clay bunds, which represents a saving in materials and an increase in the efficient use of space in the landfill site.

The first layer is preferably substantially impermeable to fluids so as to substantially prevent fluid from passing through the first layer. It is preferred that the first layer exhibits a hydraulic conductivity initial flow value of less than around l.E-09 m/s, more preferably less than around 1.E- 12 m/s when tested under a 1.0 MPa pressure (i.e. 10 bar - equivalent to 100 m head of water or 10 kg/cm ² ). The substantial prevention of fluid transfer through the first layer provides a capability of the wall lining which is preferable for many applications such as landfills and reservoirs. The thickness of the first layer may be between 50mm and 2m, and more preferably between 200mm and Im. It is preferred that the first layer additionally comprises a graded aggregate. The first layer may possess bulk density of around 1.5 to 3.5 g/cm ³ , more preferably around 2.5 g/cm ³ , measured using the method set out in BS 598-104, 2005, Pat 104. Preferably the first layer possesses an air voids content of less than around 5 %, more preferably less than around 3 %, and most preferably an air voids content of around 1 to 3 %. In a preferred embodiment of the first and second aspects of the present invention the first layer comprises dense asphaltic concrete (DAC). Characteristics of density, low fluid

permeability and structural strength make DAC eminently suitable for use as, or as a component of the first layer of the wall lining of the present invention.

The securing member preferably comprises a reinforcing portion to strengthen the structure of the wall lining and said reinforcing portion preferably comprises a generally planar mesh. A mesh support portion allows the securing member to add to the structural strength of the wall lining while allowing the first layer to form a continuous layer over the extent of the wall lining. The support portion may comprise a geogrid material, which has characteristics of toughness that provide a strong and stable wall lining. The securing member preferably further comprises an anchoring portion to anchor the securing member to the wall.

The wall lining of the second aspect of the present invention preferably further comprises a second layer, wherein the first layer is provided between the second layer and the wall.

The second layer present in the first aspect and optionally present in the second aspect of the present invention serves to protect the first layer from damage, particularly damage which would impair the ability of the first layer to act as a low permeability barrier. The second layer preferably comprises an aggregate, which may be suitably graded. The second layer may also provide a fluid drainage facility, particularly when the second layer comprises a relatively loose or low density aggregate. The provision of drainage is advantageous in that fluid is not allowed to collect near to the first layer.

In the second aspect of the present invention the second layer preferably further comprises a binder material, as specified in respect of the first aspect of the present invention. The binder material can interact with the aggregate material so as to reinforce the second layer, thereby increasing the stability of the wall lining as a whole, and so the use of binder in the second layer may supplement or completely replace any form of reinforcement provided by a reinforcing portion of a securing

member which may be provided to anchor the first bituminous layer to the wall. Preferably the second layer comprises a bituminous binder. This binder coats the aggregate present in the second layer and binds the aggregate together. The bituminous-coated aggregate representing the second layer may be considered a form of Macadam commonly used in the construction industry. The second layer is preferably less dense than the bituminous first layer. The second layer may possess an air voids content of up to around 20 %, and preferably possesses an air voids content of at least around 5 %. More preferably the second layer possesses an air voids content of around 10 to 18 %.

The wall lining preferably further comprises a facing member. The facing member defines a fixation portion embedded in the second layer so as to fix the retaining portion to the second layer and add structural support to the wall lining. The facing member increases the structural strength of the wall lining and makes the wall lining more stable. The fixation portion may define projections, the projections mechanically interacting with the second layer so as to substantially fix the fixation portion relative to the second layer. The projections increase the force required to move the facing members relative to the wall lining.

The facing member preferably further defines a retaining portion located on the surface of the wall lining structure remote from the wall. The retaining portion may therefore define at least part of the outer surface of the wall lining. The retaining portion may be substantially planar. The retaining portion provides added strength to the layers of the wall lining and also serves to protect the remainder of the wall lining from damage. The retaining portion may comprise a textile so as to more effectively retain the granular material of the wall lining. The textile may form part of a geo-composite material, which could provide an enhanced drainage function.

The wall lining structure further comprises a further securing member, the further securing member attached at a first end to the first layer and at a second end to the fixation portion of the facing member so as to secure the facing member to the first

layer. The first layer, being secured to the wall by the securing member, serves to transfer forces from the further securing member to the other securing member and thereby to the wall, increasing the structural strength of the wall lining.

The further securing member may be formed integrally with the other securing member. Such an arrangement allows direct transfer of tension forces between the two securing members.

The first end of the further securing member is preferably embedded within the first layer. The embedding allows for a secure and simple attachment of the further securing member and the first layer.

The two securing members may be separate elements, lying in the same horizontal and/or vertical plane, or they may lie in different horizontal and/or vertical planes.

The further securing member preferably comprises a substantially planar mesh, so as to provide a structural support function for the second layer. The mesh may be comprised of a geogrid material.

The wall lining structure preferably further comprises a third layer, wherein the third layer is provided on a surface of the second layer remote from the wall. The third layer preferably provides a drainage function so as to enhance the drainage capabilities of the wall lining structure.

The second layer is preferably provided between the first layer and the third layer, so as to allow fluid to drain away from the wall lining structure as soon as possible after entering the wall lining. This enhances the drainage characteristics of the wall lining structure. The third layer preferably has a minimum hydraulic conductivity approximately equal to a 500 mm thickness of material having a minimum hydraulic conductivity of l.E-04 m/s. The third layer may comprise any appropriate material, such as a drainage aggregate, which may possess a maximum

fines content of up to around 10 %, more preferably up to around 8 %, and most preferably up to around 5 %. The third layer may alternatively or additionally comprise a drainage geocomposite, in which case the minimum hydraulic conductivity and layer thickness criteria above shall be met by an equivalent in- plane transmissivity for the relevant thickness of geocomposite.

The wall lining according to the first aspect may further comprise a buffer layer provided between the first layer and the wall. The buffer layer preferably comprises a granular material so as to provide a drainage function. The first reinforcing portion of the securing member may provide structural support to the buffer layer. The buffer layer enhances the drainage capabilities of the wall lining and is preferably used to provide a more uniform surface adjacent which to provide the first layer. In certain preferred embodiments a steel mesh netting or the like is provided against the exposed face of the wall prior to the application of any layers of the wall lining itself. The mesh may be affixed to the wall using any appropriate means, such as a series of bolts provided near the top and bottom edges of the mesh. Once the mesh is in place, the buffer layer can then be placed directly against the mesh, followed by the first layer of bituminous material and any subsequent layers.

Embodiments of the present invention are now described by way of example only with reference to the accompanying figures, in which:

Figure 1 is a side elevation of a first embodiment of a quarry lining in accordance with the present invention;

Figure 2 is a front elevation of the quarry lining of Figure 1 taken on the line I-I;

Figure 3 is an enlarged side view of a segment of the quarry lining shown in Figure l;

Figure 4 is an enlarged side view of a partially completed segment of the quarry lining shown in Figure 1 ;

Figure 5 is an enlarged side view of a second embodiment of a quarry lining in accordance with the present invention;

Figure 6 is an enlarged side view of a third embodiment of a quarry lining in accordance with the present invention;

Figure 7 is an enlarged side view of a fourth embodiment of a quarry lining in accordance with the present invention; and

Figure 8 is an enlarged side view of a fifth embodiment of a quarry lining in accordance with the present invention.

In Figures 1 to 3, a lining structure 1 is shown provided against a quarry wall 2, in preparation for use of the quarry wall as the boundary of a landfill site or the like. The quarry wall 2 adjacent which the lining 1 is provided has an irregular surface but the surface defines a major plane having a gradient of a , where a is 70°, though it will be appreciated that the lining may be used to line a quarry wall defining an angle a of up to around 90°, and is particularly suitable to line a quarry wall defining an angle. The quarry lining 1 defines the boundary of a waste space 3 into which landfill waste (not shown) can be placed. The quarry lining 1 extends to cover at least part of a quarry wall 2 which borders the quarry.

The quarry lining 1 comprises a quarry-side shoulder layer 4 which is provided adjacent the quarry wall 2. Adjacent the quarry-side shoulder layer 4, an impermeable layer 5 is provided such that the quarry-side shoulder layer 4 is located between the impermeable layer 5 and the quarry wall 2. A waste-side shoulder layer 6 is provided adjacent the impermeable layer 5 such that it is situated between the two shoulder layers 4, 6. Adjacent the waste-side shoulder

layer 6, a drainage layer 7 is provided so that the waste-side shoulder layer 6 is situated between the drainage layer 7 and the impermeable layer 5. The drainage layer 7 is held in position relative to the other layers 4, 5, 6 in the lining 1 by a plurality of facing members 8, each facing member 8 being secured to the quarry wall 2 by a securing member 9. The facing members 8 and the securing members 9 also contribute to the overall structural strength of the lining 1.

As shown in Figure 3, the quarry-side shoulder layer 4 has an inner surface 10, which closely follows the contours of the quarry wall 2, and an outer face 11, which has a more uniform contour than the quarry wall 2, so as to provide a regularised and substantially uniform substrate against which the impermeable layer 5 is provided. The quarry-side shoulder layer 4 has a drainage function so as to allow precipitation, ground water and gases to drain away from the impermeable layer 5 of the quarry lining 1. The drainage capabilities of the quarry-side shoulder layer 4 are approximately equal to a 500mm thickness aggregate layer having a minimum hydraulic conductivity of 1.E-04m/s, though it will be appreciated that the drainage capabilities of the quarry-side shoulder layer 4 may be of any acceptable hydraulic conductivity. The quarry-side shoulder layer 4 comprises a combination of granular aggregate material, such as a Type 1 fill (equivalent to Type 1 granular sub-base to the UK Department of Transport Specification for Highways Works).

The quarry-side shoulder layer 4 is constructed so as to be capable of supporting weights commensurate with plant machines that would be used to apply the lining 1 to the quarry wall 2, for example approximately 40Te. Referring again to Figure 3 the quarry-side shoulder layer 4 has an average horizontal thickness of A, where A is approximately Im, though the value of A may range between around 50mm and 10m, or more preferably around 500mm and 3m depending upon the particular application. It will be appreciated that in some embodiments of the present invention, the quarry-side shoulder layer 4 may be omitted partially or completely.

The impermeable layer 5 is provided adjacent to the outer face 11 of the quarry- side shoulder layer 4 and prevents egress of liquid leachate and gases from, and ingress of precipitation, ground water and gases to, the landfill waste space 3. The hydraulic conductivity of the impermeable layer 5 is at least equivalent to an approximately 500mm thickness of clay, the clay having a maximum hydraulic conductivity of l.E-09m/s. The impermeable layer 5 comprises dense asphaltic concrete (DAC) having a 3% air voids ration, though it will be appreciated that the impermeable layer 5 may comprise any desirable asphaltic or bituminous material and may have an air voids ration of around 0% to 10% or more preferably in certain applications around 1% to 5%. The density and rigidity of the impermeable layer 5 adds to the structural strength of the quarry lining 1. With reference to Figure 3, the DAC layer 5 has a thickness B, where B is around 400mm, though it will be appreciated that the value of B may be around 50mm to 2m, and may be around 200mm to Im depending on the particular application.

The waste-side shoulder layer 6 is provided adjacent the impermeable layer 5 to protect the impermeable layer 5 from damage during use of the landfill site due to movement of waste in the landfill waste space 3 relative to the quarry lining 2. Importantly the waste-side shoulder layer 6 also provides structural support to the quarry lining 1. m particular, it is desirable that the waste-side shoulder layer 6 should be capable of supporting the weight of a plant machine of at least 40Te during construction of the lining 1. The waste-side shoulder layer 6 is of horizontal thickness C (as shown in Figure 3), where C is approximately 2.5m, though it will be appreciated that C may be around Im to 4m, and more preferably around 2m to 3m. The waste-side shoulder layer 6 comprises granular aggregate material, such as a Type 1 fill or the like, and preferably a bituminous binder to coat the aggregate and bind it together. In this way, the waste-side shoulder layer 6 can provide a significant amount of reinforcement to the lining 1, potentially obviating the need for any additional means of reinforcement, such as anchor members and/or layers of geogrid material.

The drainage layer 7 is provided adjacent the waste-side shoulder layer 6 to provide drainage for liquid leachate and waste gases from waste which, during use of the quarry as a landfill site, is located in the waste space 3. The drainage layer 7 may have any suitable hydraulic conductivity to suit a particular application and preferably has a hydraulic conductivity approximately equal to a 500mm thickness of material having a minimum hydraulic conductivity of 1.E-04m/s. The drainage layer 7 has a thickness D (shown in Figure 3), where the value of D is around 500mm, though it will be appreciated that the value of D may be around 2mm to 1500mm, or more preferably around 250mm to 750mm depending on the particular application. The drainage layer 7 comprises suitably graded drainage aggregate, optionally possessing a maximum fines content of up to around 10 %, more preferably up to around 8 %, and most preferably up to around 5 %, such as clean, non-calcareous 25 to 40 mm gravel. The drainage layer 7 may comprise a geo- composite material such as a geonet or cuspated core with thermally bonded filter geotextiles adhered to each side of the core, in which case the thickness of the drainage layer D may be around 3mm to 5OmTn;, and is preferably around 10mm. The drainage layer 7 is held in position relative to the waste-side shoulder layer 6 by a plurality of facing members 8 as will now be described in more detail.

Each of the facing members 8 has two generally planar portions: a retaining portion 12 and a fixation portion 13. The retaining portion 12 and the fixation portion 13 are generally rectangular and share one long edge. The retaining portion 12 and the fixation portion 13 are set at an angle to one another so as to define an angle β , where β is approximately equal toα so that the retaining portion 12 of each facing member 8 defines a major plane which is substantially parallel to the major plane defined by the quarry wall 2. It will be appreciated that the angle of β may be around 35° to 90°, around 45° to 80° or, in some applications, around 70°, moreover angle β may not be equal to a .

The retaining portion 12 maintains the drainage layer 7 in position relative to the waste-side shoulder layer 6 and, when the landfill site is in use, protects the

drainage layer 7 from damage due to movement of waste inside the waste space 3. The retaining portion 12 has a vertical height Y and a horizontal width Z (as shown in Figure 2). The height Y is measured perpendicular to the width Z. Y and Z may each take any appropriate value, although it is preferred that Y is around 800 mm, but may vary between around 200 mm and 2000 mm, and/or Z is around 5 m, but may vary between around 1 m and 10 m depending upon the requirements of a particular application. In a preferred embodiment, stock sheets of reinforcement fabric, 2.4m x 4.8m, are pre-bent along their major axis before being provided on site. Where a vertical height Y of 800 mm is desired, (which may equate to any desirable number of lifts, e.g. 1, 2, 3, 4 or more), the length of the retaining portion of each sheet would need to be around 850 mm to provide an angle β of around 70°, leaving a fixation portion 13 of length, X, around 1550 mm.

As shown in Figure 2, the retaining portions 12 of horizontally adjacent facing members 8 are connected together by a lateral connector 14 so as to add to the structural strength of the quarry lining 1. It will be appreciated that the lateral connector 14 may be any suitable connection arrangement.

The fixation portion 13 of the facing member 8 is set into the drainage layer 7 and the waste-side shoulder layer 6 so as to secure the facing member 8 relative to the waste-side shoulder layer 6. The fixation portion 13 has a horizontal depth X (as shown in Figure 1) and is of the same width Z as the retaining portion 12. The value of X is preferably around 1500 to 1600 mm, though the value of X may be between around 200 mm and 2000 mm. The height and depth of the facing member 8 may therefore be the same or different. It will be appreciated that the fixation portion 13 may not be the same width as the retaining portion 12 but may rather be wider or narrower as desired.

The fixation portion 13 defines along the long edge furthest from the retaining portion 12, a number of projections 15 (see Figure 3) and a support fastening 16. The projections 15 extend through the major plane defined by the fixation portion

13 into the waste-side shoulder layer 6 and contribute to securing the fixation portion 13 in position relative to the waste-side shoulder 6. The projections 15 are elongate dowels, though it will be appreciated that the projections 15 may be any appropriate shape including those forming a bodkin, or arrowhead, type arrangement. The fastening 16 fastens the facing member 8 to the securing member 9, and thereby to the quarry wall 2. It will be appreciated that the facing member 12 may be anchored to the waste-side shoulder 6 and may be fastened to the structural securing member 9 by any appropriate method.

In the present embodiment each of the facing members 8 is substantially of the same composition and construction, though it will be apparent that in some embodiments each of the facing members may differ in their composition and/or construction. Each facing member 8 is formed integrally, comprising a steel grid or mesh. The retaining portion 12 of each facing member 8 comprises a substantially planar separator geotextile 17 over the extent of the retaining portion 12, so as to prevent small elements of the drainage layer 7 from passing through the retaining portion 12. It will be appreciated that if the drainage layer 7 is or comprises a geocomposite, the geocomposite may partly or fully fulfil the role of the separator geotextile 17.

In an alternate embodiment not illustrated herein some of the functions of the facing member 8 may be fulfilled by a standard reinforced slope 'wraparound'.

Each facing member 8 is fastened to a corresponding securing member 9 so that forces acting on the quarry lining 1 are at least partially transferred to the quarry wall 2. The facing member 8 and the securing member 9 combine to provide the quarry lining 1 with adequate strength to be essentially self-supporting at the required inclination to horizontal. As shown in Figure 3, each structural securing member 9 comprises one or more rock anchors 18 and a generally planar material 19, such as a mesh of geogrid material. The material 19 is attached to the rock anchors 18 along a first edge 20 of the material 19. The securing member 9 also

adds structural support to the layers through which it passes, as the geogrid material 19 prevents movement of the aggregate material in the shoulder layers 4, 6 relative to the remainder of the lining 1 and the quarry wall 2.

The rock anchors 18 are embedded within the quarry wall 2 approximately in line with the fixation portion 13 to which they are connected so as to attach the geogrid material 19 to the quarry wall 2. It will be appreciated that the geogrid material 19 may be attached to the quarry wall 2 by any desirable means, including rock dowels. In the present embodiment the material 19 passes from the anchors 18 through three of the layers 4, 5, 6 of the quarry lining 1, without dividing the layers 4, 5, 6 completely, so as to attach the fixation portion 13 of the corresponding facing member 8 to the quarry wall 2. The geogrid material 19 is attached to the fixation portion 13 along a second edge of the material 21 remote from the quarry wall 2.

A partially constructed quarry lining 1 is shown in Figure 4. During construction of the quarry lining 1, a suitable base 22 is formed in the quarry floor either by excavating a substantially flattened surface upon which to build the lining, or by lining the base of the quarry to produce a flat surface. A series of horizontally adjacent securing members 9 are attached to the quarry wall 2 near the base 22 by rock anchors 18. Facing members 8 are attached to the securing members 9 by support fastenings 16 and horizontally adjacent facing members 8 are connected together by lateral mechanical fastenings 14. The layers 4, 5, 6, 7 of the quarry lining 1 are laid at the same time between the retaining portion 12 of the facing member 8 and the quarry wall 2 in consecutive lifts 23 of around 200mm, wherein a lift 23 is a single laying step including all of the layers 4, 5, 6, 7. The boundaries between each of the layers 4, 5, 6, 7, e.g. surface 11, are effectively vertical as the material making-up each layer 4, 5, 6, 7 is laid. To achieve the desired inclination for the quarry lining 1, subsequent lifts are successively stepped laterally inwards towards the quarry wall 2 by a sufficient amount.

As each lift 23 is laid, the waste-side shoulder layer 6, the impermeable layer 5 and the quarry side shoulder layer 4 are compacted so as to increase their density and reduce the likelihood of substantial movement of the layers 4, 5, 6, 7 after construction. When the layers 4, 5, 6, 7 of the quarry lining 1 have been laid to a vertical height approximately matching the vertical height of the respective row of facing members 8, a second row of facing members 8 and securing members 9 are attached to the wall 2 and the laying process repeated.

During laying of each consecutive lift 23, the upper surface 24 of the impermeable layer 5 of the previous lift 23 is reheated to a molten state so that the upper surface 24 will bind to the impermeable layer of material being laid in the present lift 23, thereby creating a continuous impermeable layer 5.

Figure 5 shows an enlarged section of a quarry lining 101 in accordance with a second embodiment of the present invention. Parts corresponding to those already described in relation to Figures 1 to 4 will be provided with corresponding reference numerals increased by 100 and will not be any further described, except to describe any differences in structure or function.

A quarry-side securing member 109 A comprises a geogrid mesh 119A and a number of rock anchors 118. The mesh 119A is attached along a first edge 120A to the rock anchors 118, which are embedded into the quarry wall 102. A second edge 12 IA of the quarry-side securing member 109A opposite to the first edge 120A does not pass through the impermeable layer 105 as in the first embodiment shown in Figures 1 to 3, but rather terminates and is embedded within the impermeable layer 105.

A waste-side securing member 109B comprises a waste-side mesh 119B, which is typically comprised of geogrid material. The waste-side mesh 119B is generally planar and rectangular and, along a first edge 120B, is embedded within the impermeable layer 105 at a vertical distance E from the mesh 119A of the quarry-

side securing member 109 A. The value of E is around 20 0mm, though it will be appreciated that the value of E may vary between around 0 mm and 1 m, more preferably around 5 mm to 500 mm. When E is around 0 mm, i.e. when there is no vertical separation between the quarry-side and waste-side securing members 109 A, 109B, a suitably dimensioned horizontal gap is preferably provided between the ends 120B, 12 IA of the securing members 109 A, 109B embedded within the impermeable layer 105 to ensure that a potential fluid pathway through the impermeable layer 105 is avoided. The horizontal gap (not shown in Figure 5) may be any appropriate size, such as around 5 to 30 mm, more preferably around 20 mm, depending, at least in part, upon the thickness of the impermeable layer 105.

Along a second edge 121B, which is opposite the first edge 120B, the waste-side geogrid material 119B is mechanically fastened to the fixation portion 113 of a facing member 108. The stepped configuration of the quarry-side securing member 109 A and the waste-side securing member 109B has advantages over the securing member 9 of the first embodiment in that the securing members 109 A, 109B of the second embodiment do not pass continuously through the impermeable layer 105 and therefore do not present a potential passage through the impermeable layer 105 for egress of waste leachate and gases from waste in the waste space 103 or for ingress of precipitation, ground water and gases from outside the landfill site. The securing members 109A, 109B also add structural support to the layers 104, 105, 106 through which they pass, as the geogrid material 119A, 119B prevents movement of the aggregate material in the shoulder layers 104, 106 relative to the remainder of the lining 101 and the quarry wall 102. The securing members 109 A, 109B function as structural support for the quarry lining 102 as a whole, as the impermeable layer 105 is used to transfer stresses from the waste-side securing member 109B to the quarry-side member 109A and to the quarry wall 102.

In order to achieve the stepped configuration of the quarry-side and waste-side securing members 109 A, 109B, during construction of the quarry lining 101 the

securing members 109 A, 109B may for example be placed during the laying of the same or different lifts 123 of the quarry lining 101.

Figure 6 shows an enlarged section of a lining 201 in accordance with a third embodiment of the present invention. Parts corresponding to those already described in relation to Figure 1 to 3 will be provided with corresponding reference numerals, increased by 200, and will not be any further described except to describe any differences in structure or function.

A quarry-side structural securing member 209A provides support to the quarry lining 201 by not only anchoring the impermeable layer 205 to the quarry wall 202, but also allowing some of the forces acting on the lining 201 to be transferred directly via the securing member 209 A to the quarry wall 202. Each securing member 209A comprises an elongate rock anchor 218. Each elongate rock anchor 218 is embedded at a first end 225 in the quarry wall 202 and at a second end 226 in the permeable layer 205.

Further structural support is added to the quarry lining 201 by the quarry-side shoulder layer 204 comprising a combination of aggregate such as a standard Type 1 fill and a binding agent such as a cementitious or bituminous binder. The resulting layer 204 is substantially more self-supporting than the corresponding layers 4, 104 of the first and second embodiments.

A waste-side securing member 209B is provided which is substantially similar to the waste-side securing member 109B of the second embodiment, which is described above with reference to Figure 5.

Figure 7 shows an enlarged section of a lining 301 in accordance with a fourth embodiment of the present invention. Parts corresponding to those already described in relation to Figures 1 to 3 will be provided with corresponding

reference numerals increased by 300 and will not be any further described, except to describe any differences in structure or function.

A quarry-side securing member 309A is provided that is substantially similar to the quarry-side securing member 109 A of the second embodiment, which is described above with reference to Figure 5. The quarry-side securing member 309 A in accordance with the fourth embodiment may instead be substantially similar to the quarry-side securing member 209A of the third embodiment with or without the quarry-side shoulder 304 comprising a binder material in addition to the granular material, similar to the quarry-side shoulder 204 of the third embodiment.

A facing member 308 is provided having a retaining portion 312 and a fixation portion 313, the fixation portion 313 being embedded within the drainage layer 307 and the waste-side shoulder layer 306.

The waste-side shoulder layer 306 comprises a combination of an aggregate material and a binder material such as a cementitious or bituminous binder. In this way, the waste-side shoulder layer 306 is sufficiently rigid to provide enough structural strength to support the adjacent impermeable layer 305 and, depending upon the nature of the binder used, may be affixed to the impermeable layer 305 and/or the facing member 308.

Figure 8 shows an enlarged section of a lining 401 in accordance with a fifth embodiment of the present invention. Parts corresponding to those already described in relation to Figures 1 to 3 will be provided with corresponding reference numerals increased by 400 and will not be any further described, except to describe any differences in structure or function.

A quarry-side shoulder layer 404 and a waste-side shoulder layer 406 are shown, both comprising a granular aggregate material in combination with a binder material, such as a cementitious or bituminous binder. The combination of

aggregate and binder provides enhanced structural strength to the layers 404, 406 and substantially prevents movement of the layers 404, 406 relative to the quarry wall 402. It will be appreciated that just one of the two shoulder layers 404, 406 may be provided with a binder leaving the other layer unbound and relatively loose to increase its drainage ability. By way of example, the waste-side shoulder 406 may comprise a graded aggregate and a bituminous binder (e.g. a Macadam material) and the quarry-side shoulder 404 may comprise an unbound aggregate.

In contrast to the lining 1 of the first embodiment described above, which comprised a securing member 9, the shoulder layers 404, 406 of the lining 401 of the fifth embodiment are able to stand without further reinforcement. In particular, in contrast to the above described embodiments, the impermeable layer 405 of the lining 401 of the fifth embodiment is not directly physically attached to the quarry wall 402, but rather is supported sufficiently by the neighbouring relatively rigid shoulder layer 406 or layers 404, 406. The impermeable layer 405 may be adhered to one or both of the shoulder layers 404, 406 using any desirable means of adhesion.

It will be appreciated that any of the above described embodiments may have one or both of the quarry-side and waste-side shoulder layers comprising a binder material such as a cementitious or bituminous binder in place, or in addition to, one of the other forms of reinforcement (e.g. securing members) described above. It will further be appreciated that any of the above described embodiments may be used in combination to line a single quarry wall.

In certain circumstances it may be necessary to provide some form of drainage system at the foouT^ase of the lining to provide a means of directing fluids drained from the lining away from the lining and, if desired, out of the landfill site. Any such drainage function may be achieved, for example, by constructing a horizontal layer of granular material upon which the waste is placed. One or more additional layers of similar material may be provided underneath this top layer, with one or

more drainage pipes being provided in between the layers of granular material. It will be appreciated that there should be no perforations through the landfill lining system. Pipes in fluid communication with the quarry-side drainage layer may connect to an adjacent drainage duct outside the landfill site. Any fluids to be drained from the waste-side drainage layer will be passed upwards and piped from the site. In this way, drainage on the quarry wall-side and the waste-side of the impermeable layer are kept separate.