DE20209076U1 - Combination seal system, especially for surface of waste or refuse disposal sites, has convection barrier located between capillary barrier layers - Google Patents

Abstract

The seal (4) contains a capillary barrier made from at least one mineral or recycled material. The convection barrier (7) is located between the capillary block (9) and capillary layer (8) that form the two capillary barrier layers.

Description

Combi-capillary barrier3.doc # Dr.-Ing. U. Sehrbrock # User manual Combi-capillary barrier ♦ * Page 2/7

Description Combined capital lock

Seals, particularly seals in surface sealing systems of landfills, are often constructed as multi-layer systems by combining different materials when they are designed as permanent seals. In landfill construction, sealing elements that can be described as convection barriers (e.g. plastic sealing sheets or asphalt seals) are combined with sealing components made of mineral building materials in what is known as a combination seal. In the TA Abfall and the TA Siedlungsabfall, or the Landfill Ordinance (DepV) and in Council Directive 1999/31/EC of 26 April 1999 on landfills, such combination seals are described as examples and are thus defined in terms of their basic design as the standard for landfill construction in Europe.

In the regulations applicable to landfill construction (including those cited above), it is often assumed that the mineral component of the combination seal is made of cohesive, low-permeability soils or soil mixtures (e.g. clay, bento gravel, etc.). However, comparable systems are also expressly permitted.

A proven alternative to the sealing made of cohesive earth materials, which is now recognized and established in the professional world, is the so-called capillary barrier. A capillary barrier consists of two layers: the lower, comparatively coarse-grained so-called capillary block and the upper, finer-grained so-called capillary layer. Water that penetrates into the uppermost capillary layer does not pass into the capillary block due to the jump in pore size that occurs at the interface with the capillary block, but flows downhill within the capillary layer - provided the entire system was installed with a sufficient incline.

Combi-capillary barrier3.doc # Dr.-lng. U. Sehrbrock # GelSrauohlmuster (ioniii-Kepillafspeire. * Page 3/7

The convection barrier and mineral seal components are usually combined in such a way that the convection barrier is placed above the mineral seal. In some cases, the sequence was also reversed, so that the mineral seal (here: a capillary barrier) was built on top of the convection barrier. It was essential for approval that both components were included in the sealing system. Since the convection barrier is only expected to have a limited lifespan, the mineral sealing component is conceptually responsible for ensuring continued sealing after the convection barrier fails.

In addition to the sealing components, further layers are usually required in a surface sealing system for a landfill. The overall structure can look like this in the sequence from top to bottom, as shown in Figure 1 below.

Figure 1: Surface sealing system (example)

(1) Topsoil with vegetation

(2) Recultivation or root soil

(3) Drainage layer

(4) Combination seal

(5) Gas drainage and/or base and levelling layer

(6) Subsoil or landfill body

Overall, the construction of several layers is therefore necessary in order to create a sealing system that is considered to be permanently functional and can be approved. A base and/or drainage layer is usually arranged below the combination seal, which on the one hand enables a controlled construction of the seal (base and leveling layer) and on the other hand also allows media to be drained off in a controlled manner (e.g. landfill gas). A drainage layer is usually required above the combination seal, through which the

Combi-capillary barrier3.doc # Dr.-lng. U. Sehrbrock # GetJrauctismuster Korri>i-Kapi!laispe&e · * Page 4/7

rainwater seeping through the recultivation layer is ensured.

With the invention presented here as a combination capillary barrier, some of the layers otherwise required in complex, multi-layer sealing systems become superfluous because the special arrangement of a reduced number of layers allows several tasks to be assigned, whereby the basic principle of setting up a combination seal in which the mineral components take over the sealing function alone after the convection barrier is eliminated is fully retained.

Because the convection barrier is placed between the capillary block and the capillary layer, the capillary block that is built at the bottom can function as a leveling and supporting layer and can also be used as a gas drainage layer as long as the convection barrier is functional. The capillary layer placed above the convection barrier functions as a drainage layer for the life of the convection barrier. From the point at which the convection barrier can no longer fulfil its function - because it has dissolved (in extreme cases), for example - the capillary block and capillary layer components made of mineral materials (or recycled materials) take over the sealing function as a capillary barrier. If a sealing sheet is installed as a convection barrier and it is necessary due to the expected stress, a suitable fleece can be placed below and/or above the convection barrier as a protective layer to avoid inadmissible stress on the sealing sheet.

The images, Figure 2.1 and Figure 2.2, show schematic examples of how a combination capillary barrier works in a surface sealing system. Figure 2.1 shows the initial state in which the convection barrier (7) is placed between the capillary layer (8) and the capillary block (9). Figure 2.2 shows the state after the convection barrier has been removed (dissolved). The capillary layer (8) and the capillary block (9) now lie directly on top of each other and form a capillary barrier.

Combi-capillary barrier3.doc # Dr.-Ing. U. Sehrbrock # Geliraucfesmuster fomlii-KSpitlaKpe&e , * Page 5/7

The advantages achieved with the invention are in particular that the number of layers can be reduced. This means that both the use of materials and the construction costs can be minimized. The reduced number of layers results in advantages in terms of stability, since the overall system only has a correspondingly reduced number of potential shear surfaces. In addition, the height of the entire system can be reduced. With the final height remaining the same, a larger amount of waste can be stored. A further advantage in terms of construction is that by arranging the convection barrier in the manner described, a clear separation between the capillary block and the capillary layer is provided from the outset, so that no separating element - e.g. fleece - has to be inserted to ensure the sharpest possible layer boundary. The layer boundary, which is inevitably precisely defined by the existence of the convection barrier, is maintained even if the subsoil (landfill body) subsides. As long as there is still sufficient gradient everywhere after such possible subsidence has subsided, the functionality of the capillary barrier layers is maintained. This means that the combination capillary barrier is a system that is relatively insensitive to settlement and can therefore be installed on a landfill body earlier than conventional combination sealing systems, so that there is no need to install a temporary system that can be replaced later by a permanent system in order to prevent environmental hazards and/or reduce the amount of seepage water.

In contrast to the previously occasionally used construction method, in which the capillary barrier was placed below or above the convection barrier, the combined capillary barrier requires the collection and drainage of the water collected in the drainage layer (or capillary layer) in just one level for the period during and after the functional life of the convection barrier, since the water is carried in one and the same layer in both phases. In the previous construction methods, the collection of the drainage layer is provided first and then the capillary layer, or both drainage levels are combined into one collection facility using correspondingly complex constructions.

Combi-capillary barrier3.doc # Dr.-Ing. U. Sehrbrock # Gety-auctosmuster KpmlhKapiilaispeire * * Page 6/7

The materials of the capillary layer and the capillary block can - as before - be selected on a project-specific basis according to local conditions or defined based on experience from other projects that have already been completed. However, due to the reliable separation of the capillary block from the capillary layer by the convection barrier installed between them, the grain sizes can be selected purely according to hydraulic aspects without taking into account the construction operational requirements (avoiding mixing due to construction operations).

The images, Figure 2.1 and Figure 2.2, show the combination capillary barrier as a combination seal as an example in a possible structure of a surface sealing system for landfills. Figure 2.1 shows the initial state with the convection barrier (7) still fully functional. The capillary layer (8) serves as a drainage layer, while the capillary block (9) functions as a supporting and leveling layer and/or gas drainage layer. Figure 2.2 shows the situation after the convection barrier (7) has been removed. The capillary layer (8) and the capillary block (9) now function together as a capillary barrier.

The combi-capillary barrier can be installed directly on the substrate (6), e.g. waste body, or on an existing or previously separately installed layer.

Claims (1)

Combination seal, consisting of an element serving as a convection barrier and a component consisting of mineral material(s) - or of recycled material(s) - characterized in that the component consisting of mineral material(s) - or of recycled material(s) - is designed as a capillary barrier and the convection barrier ( 7 ) is arranged between the two layers of the capillary barrier, capillary block ( 9 ) and capillary layer ( 8 ).