Geosynthetic mat

Abstract

The present invention relates to a geosynthetic mat comprising an upper cover layer and a lower cover layer, and a middle filler layer disposed between the upper cover layer and the lower cover layer and composed of a filler layer material containing an expandable material. The present invention is characterized in that the top cover layer and / or the bottom cover layer is / are composed of a biodegradable material or contain a biodegradable material, and the peel strength is characterized by the degree of residual peel strength at a predetermined time point after the start of the biodegradation process. The degree of this residual peel strength is formed by the square of the quotient of the reduced peel strength of the connection structure between the upper cover layer and the lower cover layer at a predetermined time and the initial peel strength of the connection structure between the upper cover layer and the lower cover layer before the start of the biodegradation process.

Description

Technical Field

[0001] The present invention comprises a top cover layer, a bottom cover layer, and a center filler layer disposed between the top cover layer and the bottom cover layer and comprising a filler layer material containing an expandable material, the filler layer material being a geosynthetic mat having an expansion behavior, and a connection structure in which the top cover layer and the bottom cover layer are mechanically connected to each other at a plurality of positions via a middle filler layer, the connection positions being spaced apart from each other, preferably arranged at a certain distance from each other along a straight line, whereby the upper cover layer and the lower cover layer are mechanically connected to each other at a plurality of positions via the center filler layer, the connection positions being spaced apart from each other, preferably arranged at a certain distance from each other along a straight line, whereby the upper cover layer and the lower cover layer have a peel strength with respect to each other due to the connection structure, and relates to a geosynthetic mat.

Background Art

[0002] The filler layer material has a swelling behavior, which is typically characterized by the degree of swelling determined by the ratio of the volume of the filler layer material containing water absorbed at a predetermined time point after the start of the swelling process to the initial volume of the filler layer material before the start of the swelling process. The degree of swelling is determined by completely immersing the geosynthetic mat in a water bath until a predetermined time and determining the volume of the filler layer material before immersion and at the predetermined time. Therefore, the degree of swelling indicates the swelling ability of the material in an unobstructed state and can be determined, for example, in accordance with ASTM D5890. For example, a specified amount (2 g) of dry filler layer material is placed into a 100 ml graduated cylinder containing 90 ml of water. Then, water is added up to 100 ml. The filler layer material sinks to the bottom, and the initial volume of the filler layer material can be read from the scale of the graduated cylinder immediately after adding the filler layer material. Thereafter, the filler layer material swells over a predetermined period, for example, at least 16 hours. The swollen volume can be read by determining the height of the swollen filler layer material using the scale on the measuring cylinder, and the degree of swelling can be determined by calculating the quotient with the initial volume.

[0003] A further aspect of the present invention is the use of such a geosynthetic mat and a method for manufacturing such a geosynthetic mat.

[0004] The aforementioned type of geosynthetic mat is used to form a seal on or within a soil layer. In other applications, such a geosynthetic mat can also be used to further stabilize the soil layer and / or to protect structures from mechanical or hydraulic effects or a combination thereof in areas such as waterways and the banks, levees, breakwaters, and dike structures of waterways. It can also be used to protect other thin-layer sealing components.

[0005] The functional principle of such a geosynthetic mat is that the center filler layer is usually several times thicker than the upper cover layer and the lower cover layer, and in the state immediately after production, it does not expand or harden, so it has mechanical flexibility that allows the geosynthetic mat to be wound into a roll. On the one hand, this enables the transportation of the geosynthetic mat, and on the other hand, due to this flexibility, the geosynthetic mat can be shaped according to the terrain of the ground at the installation location. Then, the geosynthetic mat is spread out at the installation location, and if necessary, it can also be covered by spreading and overlapping multiple geosynthetic mats in parallel to cover a floor area wider than the width of the geosynthetic mat in the longitudinal direction crossing the longitudinal direction of the geosynthetic mat corresponding to the roll-out direction.

[0006] After installation, the middle filler layer expands due to water absorption, which may be caused by the soil moisture at the installation location, and artificial water supply can also be carried out as needed to promote the expansion. Due to this expansion, the void volume of the middle filler layer is homogenized and reduced. As a result, after the expansion of the middle filler layer, the hydraulic conductivity parameter k 10 ideally becomes less than 5×10 -10 m / s, preferably less than 5×10 -11 m / s, and a very low hydraulic conductivity that is homogeneous and almost isotropic is achieved. However, this homogenization and reduction of the void volume require that the middle filler layer can expand without being hindered. For this purpose, the mechanical backpressure of the interconnected top cover layer and the lower cover layer is required, and as a result, the volume increase is limited within a desirable range. In certain installation situations or installation stages, such backpressure may be caused or increased by the surface pressure of the upper cover layer achieved by installing a soil layer above the geosynthetic mat by its weight. The achieved low hydraulic conductivity can provide a sufficiently high sealing effect, protecting against water retention in static or flowing water areas, sealing of landfill sites, and moisture ingress into dike structures.

[0007] Therefore, the top cover layer, the bottom cover layer, and the connection structure that joins these two cover layers perform the essential functions required for the use and properties of the geosynthetic mat. On the one hand, due to the top layer and the connection structure, the geosynthetic mat can be rolled up and handled. As a result, even after manufacturing, during transportation, and when laid at the installation site, the structure is maintained with the center filler layer positioned between the two top layers and reaches the desired thickness. After the geosynthetic mat is installed, the two cover layers and the connection structure continue to generate and maintain mechanical stability, thus generating a mechanical counterpressure against the swelling pressure of the middle filler layer, whereby the middle filler layer forms the desired high-density structure during swelling. According to the inventors, this swelling due to the mechanical counterpressure achieved by the shrinkage of the center filler layer between the two cover layers and the connection structure is the only way to achieve the desired low water permeability of the geosynthetic mat after the center filler layer has swelled, and this low water permeability should be achieved in the best case regardless of whether a specific weight layer can be installed on the geosynthetic mat.

[0008] Finally, in an installation situation where the aforementioned type of geosynthetic mat is installed obliquely on a slope, for example, the geosynthetic mat itself may form or constitute an unstable layer on the slope. To prevent the geosynthetic mat from causing slope sliding as a separation layer, the geosynthetic mat needs to have shear strength. This shear strength is achieved by the connection structure between the upper cover layer and the lower cover layer, thereby achieving a stable connection between the lower soil layer on which the lower cover layer lies and the upper soil layer on which the upper cover layer lies.

[0009] The aforementioned type of geosynthetic mat, which has properties showing good sealing performance, shear strength, and mechanical load-bearing capacity, is known as a clay sealing sheet such as the bentonite mat of Naue GmbH & Co. KG and is described in EP 0 278 419 B1.

[0010] DE19956783A1 discloses a mat for covering corpses, which is developed from the bentonite mat described in EP 0 278 419 B1. In this improved mat, by using a virus-killing or bactericidal powder instead of a sealing powder (such as bentonite), a mat is proposed that can effectively prevent active microorganisms from escaping from the burial site due to chemical and biological effects. The mat thus developed proposes a method of providing a chemical and biological barrier against microorganisms instead of sealing by expansion by using a suitable virus-killing / bactericidal filler. This is a special mat suitable for the specific purpose of covering corpses and the associated microbial risks and is not very useful for other purposes.

[0011] DE60203517T2 discloses a further floor mat based on the technology known from EP0278419B1. The purpose of this floor mat is to allow the bentonite placed in the intermediate layer to penetrate into the cavities and intermediate spaces of the adjacent floor parts and expand only there. This is aimed at filling these cavities and gaps. For this purpose, the surface layer of the floor mat needs to come into contact with the floor and dissolve under the influence of water. Therefore, the technology of this floor mat deviates from the principle of the floor mat originally described in EP0278419B1, which has the function of expanding and compressing bentonite in the intermediate layer. Instead, it aims at the rapid dissolution of the top layer so that the bentonite can move from the intermediate layer to the hollows and intermediate spaces of the adjacent soil before starting to expand and expand there. Therefore, this soil mat is basically composed of a sealing soil material, but is suitable for special applications such as sealing a soil layer with cavities and gaps by sealing these incomplete parts. It is not suitable for general sealing applications because rapid dissolution of the top layer is required.

[0012] Such well-known geosynthetic mats are installed for temporary or permanent sealing, for example, to protect a thin plastic film, as an element with a separating function, or for stabilizing a soil layer or surface. However, in some applications with morphologically changing shapes, there are long-term adverse effects from an environmental perspective. For example, when such a geosynthetic mat is used permanently, part of the geosynthetic mat may be separated by the erosion process and carried to other places by wind or water flow, which may cause pollution in undesirable locations. When such a geosynthetic mat is used temporarily, it may be possible to separate and remove the geosynthetic mat from the ground and then dispose of it. However, in many cases, since the soil layer adheres to the geosynthetic mat or the geosynthetic mat is damaged during removal, such separation and removal are impossible. In such cases, a large amount of soil is often removed, and the entire amount of the removed soil must be disposed of. Since this removed amount contains synthetic components, the waste disposal is classified as a high-pollution substance class and incurs corresponding costs.

Summary of the Invention

[0013] The present invention is based on the problem of overcoming such aforementioned drawbacks and providing a geosynthetic mat that at least satisfies and preferably exceeds the mechanical properties and sealing properties required for conventionally known geosynthetic mats.

[0014] This problem is solved by the geosynthetic mat of the type described at the beginning according to the present invention, in which the top cover layer and / or the bottom cover layer contain a biodegradable material or are composed of a biodegradable material, and the peel strength at a predetermined time after the start of the biodegradation process is the square of the quotient of the reduced peel strength of the connection structure with the top cover layer and the bottom cover layer at a predetermined time and the initial peel strength of the connection structure with the upper cover layer and the lower cover layer before the start of the biodegradation process, characterized by the residual peel strength formed thereby, and the residual peel strength is determined by a composting test in which the geosynthetic mat is completely placed in compost and composted for a predetermined time in a temperature range of 25°C or more and 65°C or less, and the peel strength is measured by a peel test at a predetermined time before insertion and after removal from the compost, or by a marine incubation test in which the peel strength is measured by a peel test at a predetermined time before insertion and after removal from seawater under aerobic conditions in seawater at a temperature of 30°C ± 2°C and a salinity concentration of 3.5 wt% ± 1 wt%, and the swelling behavior is characterized by the degree of swelling formed by the quotient of the volume of the filler layer material containing the water absorbed at a predetermined time and the initial volume of the filler layer material before the start of swelling, and the degree of swelling is determined by completely immersing the layer of the filler layer material in a water bath and applying a pressure of 4.5 N / m 2 to it. According to the present invention, for the geosynthetic mat, the swelling / degradation ratio, which is the value obtained by dividing the degree of swelling by the residual peel strength, is in the range of 1 to 5 within 1 week after the simultaneous start of the swelling process and the biodegradation process, and is in the range of 1.5 to 25, preferably with a lower limit of 2 and / or an upper limit of 15, at each predetermined time from the start point of the second month to the end point of the third month after the start of swelling and degradation.

[0015] The present invention is based on the following findings: In principle, the present invention pursues an approach of at least partially, preferably completely, replacing the synthetic components of the geosynthetic mat, which were inevitably used in previous geosynthetic mats, with biodegradable materials in order to provide an upper and a lower cover layer and a connection structure, where the upper and the lower cover layer and the connection structure comprise a biodegradable material or are composed of a biodegradable material consisting of such biodegradable materials. In the context of the present invention, a biodegradable material is understood as a material that decomposes in a short or medium-term period, meaning a period of weeks to months, up to two years or several years, for example up to ten years, in a moist environment of a soil layer that can be composed of the main components of soil, sand, clay, and mixtures of these typical soil layer components, under typical environmental conditions at the installation location of the soil. This is understood to mean that the period of weeks to months, up to two years or several years, for example up to ten years, is decomposed by biological, chemical, or biochemical processes and thereby converted into components that are harmless to the environment.

[0016] In the present invention, the reduced peel strength due to this biodegradation process is determined in a composting test, which can be carried out, for example, in the following manner. - A soil composting test under thermophilic conditions according to ISO 16929 at a temperature of 50 °C ± 5 °C; or - An aerobic marine incubation test in seawater at a temperature of 30 °C ± 2 °C and a salt concentration of 3.5 wt% ± 1 wt%; characterized thereby. Here, the materials used in accordance with the present invention are biodegradable by the aforementioned soil composting test, particularly when they are used to seal the soil layer across flowing or still water areas. When they are used to seal the soil layer within the water area or at the bottom of the water area, it is understood that they are biodegradable by the aforementioned marine incubation test. The peel strength of the biodegradable material is determined over the biodegradation period by storing the geosynthetic mat under the aforementioned environmental conditions of one of two suitable tests for a plurality of different specific periods to determine the course of the peel strength over time, and then subjecting it to a peel test after this period, such as a drum peel test according to DIN 53295, or a peel test according to DIN EN 28510-1:2014 EN, or a peel test according to ASTM D6496.

[0017] In particular, a composting environment compliant with Section 5.1 of DIN EN ISO 16929:2018-04 can be provided, that is, an environment with the following conditions for conducting a composting test. - Place the geosynthetic mat in fresh bio-waste containing a natural indigenous microbiota, and cover both sides of the geosynthetic mat with this bio-waste to a thickness of at least 30 cm. - The temperature, pH value, moisture content, and gas composition are monitored. - The composting test is carried out in a container large enough for natural self-heating to occur, and a sufficient and uniform fumigation is ensured by an air supply system. - The container can be placed in a climatic chamber with a constant chamber temperature. - When the temperature of the compost exceeds 65°C during the spontaneous thermophilic stage, the microbial diversity decreases. - To fully recover the types of thermophilic bacteria, the compost can be re-inoculated with recently generated (up to 3 months old) mature compost (about 1% of the initial total mass of the bio-waste).

[0018] For the composting test, homogeneous bio-waste of the same age and origin is used and reduced to a maximum particle size of 50 mm by shredding and sieving. Depending on the type of waste, 10% to 60% of a filler consisting of structurally stable components such as wood chips and bark with a particle size of 10 mm to 50 mm is added. The bio-waste must meet the following criteria: - The C / N ratio of the mixture of fresh bio-waste and filler is 20 to 30 and can be equalized with urea if necessary. - The moisture content is 50% by mass or more, but there is no free moisture. - The loss on ignition of the dry residue is 50% by mass or more. - The pH value is 5 or more.

[0019] As characteristics of the dioxinetic mat according to the present invention, in addition to the peel strength, the swelling behavior is also considered, and the characteristics are set in relation to the peel strength. According to the findings of the present inventors, since the desired compression characteristics of the center filler layer are not sufficiently reflected, the pure degree of swelling cannot be used as a characteristic parameter for the desired long-term sealing characteristics of the dioxinetic mat in many applications. Instead, the middle filler layer is formed or characterized by a degree of swelling representing an increase in volume under a certain pressure, and this degree of swelling is realized in the test as the contact pressure on the material layer, for example, by a plate or disk having a corresponding weight.

[0020] The degree of expansion should be considered at least for the first month and the subsequent two months. In principle, the degree of expansion can also be considered over a longer period, and as a result, particularly in the case of a middle filler layer that expands very slowly, good adjustment of the properties is possible. For some materials, for example, because they are very dry and water-absorbent from the manufacturing process, it is necessary to consider that they already undergo initial expansion when stored in the air. In such cases, in order to avoid falsification of the results due to non-representative initial effects that may occur in the first few hours or the first few days of the expansion test, it should be understood that the material is used in the expansion behavior test of the present invention only under the realistic conditions of intermediate storage in the air and the expansion that occurs during that process.

[0021] A decisive factor for the geosynthetic mat to function is that, on the one hand, the connection structure with the upper and lower cover layers always maintains sufficient backpressure against the expansion of the middle filler layer, whereby the middle filler layer is sufficiently compressed, and in particular, the pores of the middle filler layer are closed during the first few months. Thereby, the required airtightness is achieved and can be maintained over a long period, especially after biodegradation has progressed to such an extent that the expansion asymptotically approaches the maximum expansion degree and the peel strength significantly decreases or approaches zero.

[0022] On the other hand, in many applications, it is important that the geosynthetic mat always exhibits mechanical properties after installation and prevents slipping when installed on a slope. According to the present inventors, in the initial stage where the stabilization function of the middle filler layer has not yet developed, in order to maintain the shear strength through the biodegradable structure, the decrease in the peel strength against expansion at the initial stage is decisive.

[0023] The period during which the desired properties characterized by the expansion / degradation ratio must exist ranges from a few weeks to one or two years from the start of expansion and biodegradation.

[0024] The use of such biodegradable materials can, in principle, reduce or completely avoid the problems of pollutant diffusion and contamination after the removal of such geosynthetic mats. However, the use of biodegradable materials may not generate or may not generate sufficient backpressure when the middle filler layer expands, resulting in excessive water permeability of the geosynthetic mat after expansion and the inability to achieve the desired sealing function. Generally, there is a problem that the sealing effect of the geosynthetic mat cannot be obtained by biodegradation. On the other hand, due to the biodegradation of the top layer and the connection structure, the shear strength of the geosynthetic mat decreases, and when it is installed obliquely on the slope, slip of the slope layer occurs. Therefore, the use of biodegradable geotextiles is considered important or inappropriate in many applications regarding the time requirements of the mechanical bonding effect, and DIN EN 12225 stipulates the test criteria for geosynthetics to demonstrate general resistance to biodegradation.

[0025] The geosynthetic mat according to the present invention overcomes these problems by the behavior of biological degradation and the expansion behavior adjusted in time. For this purpose, the composite of the upper cover layer, the lower cover layer and the connection structure is characterized according to the degree of residual peel strength shown by this composite according to the biodegradation rate after a certain biodegradation period, that is, after a predetermined time after the start of the biodegradation process over the subsequent period. This residual peel strength characterizes the composite of the two cover layers and the connection structure from the viewpoint of how quickly its peel strength decreases over time due to the biodegradation process. That is, it represents a curve reflecting the peel strength of the biodegradable material during the biodegradation period. The slope of the curve at any point in time can be defined as the degree of decrease in peel strength. The more the biodegradation progresses, the lower the degree of decrease in peel strength, and the earlier the biodegradation, the steeper the curve of the degree of decrease in peel strength over time, and as a result, the peel strength of the composite material decreases rapidly. The degree of decrease in peel strength can be caused by the biodegradation of the top cover layer, the bottom cover layer and / or the connection structure, or by the decrease in the fastening strength of the connection structure in the top cover layer or the bottom cover layer.

[0026] On the one hand, the filler layer material of the middle filler layer has an expansion ability, which is characterized by the water absorption and expansion ability of the filler layer material. This expansion ability is characterized by the expansion lift degree, 4.5 N / m 2 represents the increase in the volume of the filler layer material at a certain time after the start of expansion relative to the dry volume of the filler layer material before the start of expansion under a compressive load of, and generates a time-dependent curve reflecting the increase in the volume of the filler layer material over the expansion time. The higher the degree of expansion, the higher the ability of the filler layer material to expand under load. It should be understood that the degree of expansion of the material is determined without restricting the movement of expansion, that is, when determining the degree of expansion, the water content or volume of the material can be increased without being hindered. In practice, when measuring the degree of expansion, this can be achieved by performing a force control test or by placing a plate that can move freely vertically on the filler layer material with a weight of 4.5 kg per square meter.

[0027] The ratio of the degree of expansion of the expandable material of the center filler layer, the biodegradable materials of the upper cover layer and the lower cover layer, and optionally the biodegradable material of the connection structure, to the residual peel strength of the composite material of the upper cover layer, the lower cover layer and the connection structure is between 1 and 5 over the first week, and between 1.5 and 25, preferably between 2 and 15, from the beginning of the second month to the end of the third month. On the one hand, for the center filler layer, and on the other hand, for the mechanical composite surrounding this center filler layer, these two material properties are continuous with each other and adjusted over time, so that in the initial stage of expansion of the center filler layer, the upper cover layer, the lower cover layer, and the connection structure between these two cover layers build up a mechanical counterpressure that is sufficiently high against the expansion pressure and can maintain it over a long period of time to achieve sufficient compression of the center filler layer during this expansion process. Furthermore, the upper and lower cover layers and, optionally, the connection structure are biodegraded at a later point in time when this expansion is mostly or completely completed, and as a result, when the geosynthetic mat is removed, or when part of the geosynthetic mat has moved due to erosion, it is achieved that no pollutant load occurs.

[0028] According to the findings of the inventors, due to sufficient homogenization and reduction of the void volume, the middle filler layer can exhibit an overall shear strength in at least the same range as, or even exceed, the shear strength of the geosynthetic mat immediately after installation, i.e., the initial peel strength of the composite of the non-expanded middle filler layer with the upper cover layer, the lower cover layer, and the connection structure. This can reliably prevent the risk of slope sliding due to the unstable layer level of the geosynthetic mat.

[0029] The geosynthetic mat according to the invention achieves a sufficiently high impermeability due to this composition, the ratio of material properties regarding the swelling behavior of the middle filler layer, and the degradation of the mechanical properties of the upper and lower cover layers due to the achievable compression, while at the same time avoiding the risk of slope slippage and thus providing the desired hydraulic and mechanical properties in the medium and long term without the associated pollutant load. Thus, the geosynthetic mat according to the invention can be installed without the risk of local environmental pollution and environmental hazards due to erosion and transport to other locations, provided that the middle filler layer consists of or contains an environmentally compatible material and can be removed and disposed of in a cost-effective manner in the case of temporary use.

[0030] The range of the ratio of the degree of swelling maintained for the first three months to the residual peel strength enables the achievement of a balanced development of the impermeability of the geosynthetic mat due to swelling and the provision of the mechanical strength of the soil layer even when installed on a slope and exposed to the corresponding shear force.

[0031] In particular, after simultaneously starting the swelling process and the biodegradation process from the third day, it is preferable that the swelling / degradation ratio within one week is in the range of 1.2 to 5. When the geosynthetic mat and a heavy soil layer are installed thereon, the particularly preferable swelling / degradation ratio in the first week is 1.25 to 4, preferably 1.25 to 3. When the geosynthetic mat is installed without the upper soil layer, the particularly preferable swelling / degradation ratio in the first week is 1 to 4, preferably 1.2 to 3. In principle, the invention is preferably realized for different installation situations such that the swelling / degradation ratio in the first week from the third day is in the range where the lower limit is 1, or 1.25, or 1.5, or 2, and the upper limit is 1.75, or 2, or 4, or 6.

[0032] From the beginning of the second month to the end of the third month after the start of inflation and decomposition, the inflation / decomposition ratio is preferably in the range of 1.75 to 20, preferably the lower limit is 1.75 or 2 or 2.5 or 3, and / or the upper limit is in the range of 25 or 20 or 15 or 10.

[0033] It is preferable that the inflation / decomposition rate from the third month to the end of the twelfth month after the start of the inflation process and the biodegradation process is in the range of 2 to 50, preferably the lower limit is 3 and / or the upper limit is in the range of 30.

[0034] Such a long period records the long-term inflation and decomposition processes of the geosynthetic mat, and the properties of the geosynthetic mat are such that optimal inflation and decomposition behavior is achieved over this long period.

[0035] According to the findings of the present inventors, various effects can be advantageously realized by adjusting and reducing the peel strength on the one hand and the inflation on the other hand. For example, at the initial stage of the inflation process, a significant increase in weight and volume occurs regularly. At this time, in order to achieve as dense a structure as possible in the center filler layer, a high back pressure against the inflation pressure is required. The inflation of the middle filler layer causes compression and mechanical stabilization there, which on the one hand results from the inflation itself under the back pressure that can be achieved with many materials that can be used for the inflatable middle filler layer, but also brings about a stabilized middle filler layer through a chemical process. For example, the phyllosilicate contained in the middle filler layer can change into another phyllosilicate during the inflation process. For example, sodium bentonite can change into calcium bentonite, thereby providing greater strength and stability against the shear force from the middle filler layer itself. Therefore, this conversion process in the middle filler layer reduces the peel strength of the stabilized top layer and the connection structure as the degree of inflation increases, and the top layer and the connection structure will be completely destroyed at a later point in time.

[0036] This typical example is a center filler layer comprising or consisting of a mineral mixture called bentonite, which is mainly composed of montmorillonite in powder or granular form. This mineral mixture changes from an initial state containing a sodium bentonite component to an expanded state in which the calcium bentonite component is converted, and the shear strength increases during this process. According to the inventors' findings, calcium ions required for ion exchange are often already contained in sufficient amounts in bentonite, and additional amounts are always present in the surrounding soil, so this process may be accelerated. Over time, ion exchange occurs from sodium (monovalent) to calcium (divalent). How quickly this process occurs depends on the surrounding circumstances.

[0037] Particularly preferably, the degree of swelling is greater than 1.25, preferably greater than 1.5 or 2, one week after the start of the swelling process, and / or the degree of swelling is greater than 1.5, preferably greater than 2 or 3, one month after the start of the swelling process, and / or the residual peel strength is less than 0.95, preferably less than 0.9 or 0.8, three months after the start of the swelling process, and / or the residual peel strength is less than 0.9, preferably less than 0.75 or 0.5, twelve months after the start of the swelling process. In principle, the swelling behavior means that the filler layer swells to an appropriate extent over time, and the biodegradation behavior means that the peel strength decreases to an appropriate extent over time. According to this further development, not only is the ratio of swelling to biodegradation set within a certain range, but also the swelling behavior and the decrease in mechanical strength due to biodegradation are each separated into a range of advantageous values that achieve favorable swelling and appropriate biodegradation over time. In many applications, rapid swelling for sealing purposes is first important, whereas biodegradation can occur and is desirable over a longer period.

[0038] It is particularly preferred if the connection structure comprises needling between an upper cover layer and a lower cover layer or is formed by such needling. In the case of needling, a barbed needle serving as a tool penetrates the top layer and hooks onto the opposite top layer, whereby several individual fibers are pulled from this top layer through the middle filler layer. Preferably, such needling can be carried out when the penetrated top layer and / or the opposite top layer are designed as a non-woven layer, i.e., a layer having an irregular fiber structure in which fibers are drawn out during the needling process and can be fixed to the opposite layer to form the connection structure. However, needling is also possible when the top layer to be fixed is formed with a regular fiber structure, such as a knitted, crochet or woven top layer. In that case, since the fibers in the non-woven layer have good mobility in the direction perpendicular to the layer plane, it is preferably always started from the non-woven layer which is the top layer. Needling can be used in particular to provide a connection structure that connects the upper cover layer and the lower cover layer to each other at a large number of points dispersed on the surface of the geosynthetic mat and spaced apart from each other, thereby achieving a connection between the two cover layers that acts substantially over the entire surface of the upper cover layer and the lower cover layer and can thus act particularly effectively against expansion pressure and shear forces. If the connection structure, in particular the top layer perforated to form the needling, comprises fibers containing a thermoplastic (e.g., PLA, PBS, PBAT), the fibers can be additionally fixed to the back of the second top layer by melting, increasing the initial internal shear bond of the geosynthetic mat. This can be done, for example, by a frame bar that melts the fiber portion protruding outward from the second top layer and forms small nodules that prevent or impede the fibers from being pulled out from the second top layer in the direction of the first top layer.

[0039] It is more preferable if the upper cover layer and / or the lower cover layer and / or the connection structure are made of fibers of a biodegradable material or are formed by such biodegradable fibers. By using fibers made of a biodegradable material, on the one hand, good strength and the possibility of needling can be achieved, and on the other hand, such fibers can be biodegraded particularly well in a targeted manner, thereby providing the desired ratio of the degree of inflation lift to the degree of residual peel strength.

[0040] It is even more preferable if the biodegradable materials of the upper cover layer and the lower cover layer are different from each other, or if the biodegradable materials of the upper cover layer and the lower cover layer are the same. According to this embodiment, in the first embodiment, the biodegradable materials of the upper cover layer and the lower cover layer are different, which can be advantageous in specific installation situations and soil structures in order to adapt the geosynthetic mat to the local requirements of the upper and lower surfaces. In contrast, the second alternative is advantageous in many applications where the biodegradable materials of the upper cover layer and the lower cover layer are the same, that is, where the two cover layers are made of the same material. This embodiment enables a harmonious and similar degradation behavior of the upper cover layer and the lower cover layer and enables a preferred selection of the connection structure between similar materials, and thus is suitable for many applications.

[0041] According to a further preferred embodiment, the biodegradable material of the connection structure is different from the biodegradable material of the upper cover layer and / or the bottom cover layer, or the biodegradable material of the connection structure is the same as the upper cover layer or the bottom cover layer. Also in these two preferred embodiments, the biodegradable material of the connection structure may again be different from the biodegradable material of the upper cover layer and / or the lower cover layer in certain installation situations, for example, when a particularly high shear strength or a shear strength acting over a long period is required to achieve a slower biodegradation behavior of the connection structure compared to one of the cover layers or the cover layers. On the other hand, in many common installation situations, it is advantageous for the biodegradable material of the connection structure to be the same as the biodegradable material of the upper cover layer or the lower cover layer, or both cover layers, thereby obtaining production advantages due to material similarity.

[0042] It is further preferred that the top cover layer and / or the bottom cover layer comprises a non-woven layer of biodegradable material or is formed by such a non-woven layer. When the top layer is formed as such a non-woven layer or comprises such a non-woven layer, the non-woven layer achieves sufficient shear force transmission to the adjacent soil layer due to its surface structure, and on the one hand enables good adhesion support and shear force transmission from the surrounding soil layer to the geosynthetic mat. The fleece layer is also suitable for needling as described above, so that an efficient connection structure can be formed. The fleece layer is a fiber layer in which the fibers are present in a random order and have continuous fibers with a medium length in the range of about 6 cm to several meters or more. The non-woven layer preferably consists of fibers having at least two, preferably more, different fiber thicknesses, where the different fiber thicknesses are understood as a difference of at least 100%, i.e., a difference in which the non-woven layer contains fibers having a first diameter and fibers having a second diameter twice the first diameter. By using such a non-woven layer with a non-uniform fiber thickness, it is often possible to well adapt the biodegradation behavior to the swelling behavior of the middle filler layer.

[0043] It is more preferable if the upper cover layer and / or the lower cover layer comprises or is formed by a regular fabric layer, in particular a knitted, woven or crocheted fabric layer of biodegradable material. According to this embodiment, an upper cover layer or a lower cover layer having a regular structure of fibers is provided, whereby a high strength of the cover layer in the longitudinal and transverse directions is achieved, in particular as compared to a non-woven layer. Furthermore, if a dense mesh arrangement of the fibers in the fabric layer is achieved, a lower liquid permeability can often be achieved.

[0044] It is more preferable if the center filler layer comprises or is formed by a mixture of an expansive material, such as bentonite powder, in particular sodium bentonite, and a non-expansive aggregate, such as an inorganic bulk material, such as granular material, in particular sand, glass granules, chalk or coal granules. According to this embodiment, a mixture of an expansive material and a non-expansive aggregate is arranged in the center filler layer. Both materials are present in the form of bulk materials and are preferably uniformly mixed. According to the findings of the inventors, the addition of such aggregates can significantly increase the load-bearing capacity of the middle filler layer against shear forces, thereby favorably influencing the mechanical properties of the geosynthetic mat after extensive or complete biodegradation of the two cover layers and the connection structure, and enabling installation and retention on steep slopes. The mixture can be designed to have a ratio of at least 20% by weight of the expansive material and at least 20% by weight of the aggregate, or at least 30% or 40% by weight of the expansive material and at least 30% or 40% by weight of the aggregate.

[0045] It is more preferable when the center filler layer contains a curing agent or a curing liquid, particularly a hard oil such as linseed oil or tung oil. In this case, the liquid preferably exists only in a partial region such as a partial cross-section of the center filler layer. The addition of such a curing liquid or curing-inducing liquid can further enhance the mechanical elasticity against, in particular, the shear stress on the center filler layer or the erosion effect acting on the surface, thereby compensating for the biodegradation of the cover layer and the connection structure. A curing liquid is, for example, a liquid that changes from a liquid state to a solid state by cross-linking of a polymer or evaporation of a solvent component. On the other hand, a curing liquid is a liquid that reacts with other components of the filler layer, thereby promoting the curing of the filler layer. The liquid can be distributed throughout the entire center filler layer and the entire cross-section of the center filler layer, but can also be selectively applied only to partial regions, such as the grid tracks, longitudinal tracks or transverse tracks of a geosynthetic mat. Further, the liquid can exist only in a partial cross-section of the center filler layer, for example, only in the surface region of the center filler layer or only in the central region of the cross-section of the center filler layer.

[0046] The geosynthetic mat is further formed by an upper barrier layer disposed adjacent to the upper cover layer and / or a lower barrier layer disposed adjacent to the lower cover layer, and it is more preferable when each barrier layer is formed by a film, particularly a film made of a biodegradable material. Here, preferably, the upper barrier layer is disposed between the upper top layer and the center filler layer, the lower barrier layer is disposed between the lower top layer and the center filler layer, the upper top layer is disposed between the upper barrier layer and the center filler layer, or the lower top layer is disposed between the lower barrier layer and the center filler layer. Such a barrier layer can prevent the expansion promoting substance or the expansion inhibiting substance from penetrating from the formation adjacent to the geosynthetic mat into the middle filler layer, thereby having an unpredictable and unfavorable effect on the expansion behavior of the middle filler layer. This type of barrier layer enables a slow and planned expansion behavior according to the increase in soil moisture and the target value of irrigation, and is compatible with the biological degradation behavior of the connection structure and the cover layer. Such a barrier layer can be provided by a polyethylene film, but a film made of a biodegradable plastic can also be used for the barrier layer. In particular, a biodegradable material suitable for the upper cover layer or the lower cover layer can be used for the barrier layer. The barrier layer can also be applied in the form of a coating (in-line extrusion) during the manufacturing process of the geosynthetic mat, or can be applied as a finished film by lamination or adhesion, etc.

[0047] According to a further preferred embodiment, the biodegradable material of the upper cover layer, lower cover layer and / or connection structure comprises or consists of fibers, which fibers comprise a fiber core strand of a first biodegradable material and a fiber core strand sheath of a second biodegradable material surrounding the fiber core strand, and the first biodegradable material has a first biodegradation rate higher than the second biodegradation rate of the second biodegradable material. According to this embodiment, the upper cover layer and lower cover layer and / or connection structure comprises fibers composed of fiber core strands and fiber core strand sheaths, and the fiber core strands and fiber core strand sheaths are composed of two materials having different biodegradation rates. According to the inventors, this fiber design achieves the great advantage that the degradation behavior of the fiber, and thus the decrease in tensile strength, occurs discontinuously, i.e., in two consecutive different degradation phases. In the first stage, the coating of the fiber core strand is biodegraded first, but the fiber core strand is still protected by the fiber core strand sheath from influences that cause biodegradation, such as radiation or the influence of liquids, and thus either does not undergo biodegradation or undergoes only slight biodegradation. Therefore, since the fiber core strand completely or almost completely retains its mechanical properties in this first stage, if the mechanical properties of the fiber are mainly characterized by the mechanical properties of the fiber core strand, the fiber does not lose or hardly loses its mechanical properties during this first stage of biodegradation of the fiber core strand sheath. Only after the fiber core strand sheath has been decomposed does the fiber core strand undergo biodegradation, as a result of which the mechanical properties of the fiber are significantly reduced. Therefore, the fibers produced in this way initially have a very slow decrease in mechanical properties and then, at a certain point, an increase in mechanical properties. This is advantageous for the geosynthetic mat according to the invention in many applications, since sufficient mechanical strength can be provided by the cover layer and connection structure over a certain period, which mechanical strength can, for example, correspond to the typical swelling behavior or typical conversion behavior of the middle filler layer, but after this period, rapid biological complete degradation of the cover layer and connection structure and the corresponding decrease in mechanical strength are achieved.

[0048] The first biodegradable material comprises natural fibers such as coconut fiber, jute fiber, hemp fiber, bamboo fiber or linen fiber, or biodegradable synthetic fibers of PBS, PBAT, PLA or a polymer blend of at least two of these materials, or the biodegradable material comprises a mixture of natural fibers and a fiber core of synthetic fibers, preferably with the weight ratio of synthetic fibers being greater than 30%, more preferably greater than 50%. The use of these fiber materials or a mixture of these fiber materials has proven to be particularly suitable for many applications in order to achieve the mechanical strength and biodegradation rate required for a geosynthetic mat using an expandable material in the middle filler layer.

[0049] It is even more preferable when the second biodegradable material comprises a biodegradable polyester such as a cellulose-based plastic, a starch blend, lyocell, succinic acid (PBS), polybutyrate adipate terephthalate (PBAT) or polylactic acid (PLA). These materials have proven to be particularly suitable as coating materials because they not only exhibit a sufficiently slow biodegradation behavior but can also be easily applied as a liquid coating. It should be understood that the fibers of the top layer or the connecting structure can be designed such that they are already coated before the fiber material is processed into the top layer, i.e., the top layer is made of coated fibers. Alternatively, it is also possible to manufacture a cover layer from uncoated fibers, i.e., from the fiber core strands only, and then coat the entire cover layer with the second biodegradable material so as to also cover the cut fiber ends, and achieve the strengthening of the cover layer by the adhesion effect at the intersection of the fibers by the second biodegradable material.

[0050] The middle filler layer is from 1×10 -5 to 1×10 -5It is even more preferable to have a water permeability between m / s. According to this embodiment, the geosynthetic mat comprises a center filler layer that initially has insufficient water permeability in the as-manufactured state prior to installation in order to achieve a reliable sealing of the soil layer. According to the inventors, such water permeability is initially acceptable in many applications or even desirable to achieve the penetration of the geosynthetic mat at the initial stage after installation. During this penetration, the particles contained in the water penetrating the geosynthetic mat accumulate in the middle filler layer, leading to the compression and sealing of the middle filler layer, similar to a clogging filter. That is, a clogging process occurs corresponding to the accumulation of a filter cake within or on the middle filler layer. Thereby, a preferable sealing effect can be achieved with a particularly low water permeability and a particularly high sealing level of the geosynthetic mat. In the first stage, the geosynthetic mat functions only as a penetration barrier and only after a certain penetration stage does it finally acquire and then retain its ultimate impermeability. According to the inventors, this structure of the geosynthetic mat is particularly suitable for forming a seal on the bed of a flow carrying a liquid such as a stream or a river, taking advantage of the fact that the liquid of the stream or river carries together the corresponding particles that can function as a seal. According to one aspect of the invention, this also includes a geosynthetic sheet in which the middle filler layer is composed of a material having very low swelling capacity or a non-swelling material, i.e., a material having a swelling degree lift of 1 over the entire installation period. For example, a middle filler layer made of sand or other injectable mineral materials can be used for such a sealing effect by corimation.

[0051] A further aspect of the present invention is a geosynthetic web comprising at least one layer comprising or formed by fibers, the fibers comprising a fiber core strand of a first biodegradable material and a fiber core strand sheath of a second biodegradable material surrounding the fiber core strand, the first biodegradable material having a first biodegradation rate and the second biodegradable material having a second biodegradation rate different from, and in particular higher than, the first biodegradation rate of the first biodegradable material. For the purposes of the present invention, a geosynthetic sheet is understood to be a structure having longitudinal and transverse dimensions many times its thickness, such as a geosynthetic mat. The geosynthetic mat and the geosynthetic sheet may in particular have longitudinal dimensions that are multiples of the transverse dimensions. That is, the length may be overwhelmingly longer than the width. Therefore, geosynthetic mats and geosynthetic sheets are usually transported in a rolled or folded state and are unrolled or deployed in a rolled or folded state so that they can be laid longitudinally at the installation site. In the understanding of the present invention, a geosynthetic mat should be distinguished from a geosynthetic sheet, and a geosynthetic mat has a plurality of layers, while a geosynthetic sheet can have only a single layer or can also have a multi-layer structure.

[0052] The geosynthetic sheet according to the present invention is characterized by being formed from fibers having at least a two-layer structure or having such fibers. The fibers have a fiber core strand and a fiber core strand sheath covering the fiber core strand. The fiber core strand and the fiber core strand sheath are composed of two different biodegradable materials having different biodegradation rates, that is, under the same biodegradation conditions, the first material is biodegraded faster or slower than the second material. Preferably, the second material has a biodegradation rate lower than that of the first material, that is, the second material biodegrades more slowly than the first material.

[0053] As described above, the geosynthetic mat can also have fibers or fiber layers formed in at least two layers. Such fiber designs achieve a more favorable progression of the mechanical strength during biodegradation of the fibers or the layers made from the fibers. In particular, it is possible to maintain a high mechanical strength over a longer period, especially while the fibers are in the first stage, i.e., only the fiber core strands of the layers made from the fibers are biodegradable. In particular, during the first stage, i.e., while only the fiber core strand sheath is biodegradable, the fibers maintain a high mechanical strength over a long period. Subsequently, in the second stage where the fiber core strands are decomposed after the decomposition of the fiber core strand sheath, the mechanical strength of the fibers rapidly decreases. It should be understood that these characteristics and further embodiments described above in relation to the geosynthetic mat are also applicable to the geosynthetic sheet and are accordingly referred to.

[0054] According to a preferred embodiment, it is provided that the fibers in the layered sheet are present as an irregular structure, particularly as a non-woven layer, or as a regular structure, particularly as a knitted, woven, or crocheted fabric layer. Thus, the special fibers of this geosynthetic sheet can, for example, be present as an irregular structure as a non-woven layer, and as a result, the above-described characteristics and advantages that also occur in relation to the above-described geosynthetic mat are obtained. Alternatively, the fibers can also be processed to be arranged in a regular structure, i.e., knitted, woven, or crocheted, or in the manner indicated by other methods. Thereby, the regular structure is typically understood as a structure in which the geometric pattern of the fiber paths is regularly repeated along a linear direction or two intersecting linear directions, as already understood for the geosynthetic mat. For the regular structure, reference is also made to the characteristics and advantages described above for the geosynthetic mat.

[0055] Next, by coating the fibers in the circumferential and end directions with a fiber core strand coating, a geosynthetic sheet can be further developed. Specifically, in the first step, a fiber core layer is manufactured from fiber core strands, and then in a subsequent second step, a layered sheet is manufactured by coating the fiber core strands of the fiber core layer with a coating material, thereby further developing the geosynthetic sheet. Such an embodiment of coating the circumference and end faces of the fiber core strands with a fiber core strand coating can be achieved, in particular, by first manufacturing a layered ply from the fiber core strands, for example by processing into a non-woven fabric, or weaving, or knitting, and then coating the pre-manufactured layer of fiber core strands with a fiber core strand coating, for example by immersing in a liquid, or spraying or wetting with a liquid in a coating process, thereby coating the fibers on all sides. To achieve the biodegradable properties in the desired manner, this processing method is more advantageous and preferred over a process in which the fibers are processed after being completely pre-manufactured, because in this processing method, the end face fiber core strand cross-section ends are exposed by the required separation of the fibers and are thus more susceptible to rapid biodegradation.

[0056] A further aspect of the present invention is a geosynthetic mat having the structure and function described above, wherein the upper and / or lower cover layers comprise or are formed by a geosynthetic sheet having the structure and function described above. As described above, the properties of such a geosynthetic sheet containing two layers of fibers can be particularly advantageously used in the geosynthetic mat according to the present invention.

[0057] Yet another aspect is to use the geosynthetic mat of the above-described construction method or the geosynthetic sheet of the above-described construction method to produce a sealing layer on the ground or the bottom of a water area. As already explained above, the geosynthetic mat according to the present invention and the geosynthetic sheet according to the present invention are particularly suitable for manufacturing a sealing layer in the ground and, furthermore, are suitable for manufacturing such a sealing layer on the bottom of a water area. The well-balanced property of imparting mechanical peel strength to the first stage of swelling of the middle filler layer is particularly effective and can achieve reliable sealing. On the other hand, the biodegradation of the cover layer, the connection structure, and the additionally provided barrier layer significantly reduces or completely avoids environmental pollution when removing the geosynthetic mat or geosynthetic sheet, or when a part of the geosynthetic mat or sheet is discharged by erosion.

[0058] This use can be advantageously continued by spreading the geosynthetic mat in a first step and subsequently impregnating the geosynthetic mat with a liquid, particularly a hard oil, in a second step. In this method of use, first, the geosynthetic mat or geosynthetic sheet is prefabricated almost completely by manufacturing the layers, arranging them in relation to each other, and joining them. Next, the geosynthetic mat or sheet prefabricated in this way is wound up so that it can be transported. The geosynthetic mat or geomembrane transported to the installation site is spread out for laying and then moistened with a liquid that affects further mechanical and / or biological behavior at the installation site. In this way, by impregnating the geosynthetic mat or geomembrane only at a second point following the manufacturing time of the geosynthetic mat or geomembrane, it is possible to prevent the properties of the geosynthetic mat or geomembrane from changing during storage or transportation due to impregnation by the liquid that has already occurred. Instead, it ensures that the influence of the desired functional and structural properties by the liquid starts only at the installation site following the wetting by the liquid that occurs there.

[0059] This impregnation is processed in a pre-manufacturing step to form, for example, a cover layer, a connection structure, etc. of a geosynthetic mat or sheet, and may also be constituted by a coating of a fiber core strand that is subsequently given an additional coating on-site to favorably affect biodegradation behavior and mechanical properties. It should be understood that this is also possible.

[0060] The wetting / impregnation can be carried out, in particular, in such a way that it is selected as a function of the pre-measured environmental conditions of the installation site. For example, it can be carried out by adapting the layer thickness to such environmental conditions, or by selecting the liquid in which the impregnation is carried out from a plurality of different available liquids, or by mixing them. Environmental conditions that affect this selection or the impregnation intensity include, for example, the moisture content of the soil, the pH value of the soil, the concentration of substances that promote or retard the biodegradation process in the soil, the UV intensity at the installation site, and other influencing factors. In principle, in such use by pre-wetting, it should be understood that even if the liquid used for impregnation has not yet caused biodegradation, the swelling degradation ratio is determined, and the time within a predetermined range must be determined from the time when the geosynthetic mat was impregnated.

[0061] According to a further preferred embodiment of the use according to the invention, the geosynthetic mat is impregnated with a liquid at a first point before laying, thereby causing pre-expansion of the center filler layer, and then installed at the installation location at a second point, in particular by supplying liquid from the surrounding soil, it can be provided to expand at the installation location. According to this embodiment, it is envisaged that the geosynthetic mat or sheet is impregnated with a liquid before being laid, thereby causing pre-expansion of the center filler layer. The pre-expansion referred to here is understood as a limited expansion in which the material of the center filler layer has not yet exhausted its maximum expansion capacity, that is, it has not yet expanded to the maximum, but has only exhausted a part of this expansion capacity. Such impregnation with a liquid for this pre-expansion can already be carried out, for example, during the production of the geosynthetic mat or geomembrane, but alternatively, the geosynthetic mat is produced at a first point and the geosynthetic mat is impregnated for pre-expansion at a second point, for example, immediately before the delivery or transportation of the geosynthetic mat. When transporting the geosynthetic mat to the installation site, avoid the influence of changes in the geosynthetic mat during storage from the time of production to the time of transportation. The pre-expansion can favorably promote the initial expansion behavior of the geosynthetic mat in the days to weeks immediately after installation, play a role in having a positive impact, and thereby avoid unfavorable structural changes and changes in mechanical properties.

[0062] The liquid with which the geosynthetic mat is impregnated at the first point may correspond to or be similar to the liquid that also causes expansion at the installation site, for example, it may be composed of impregnation with water. However, in other applications, the liquid with which the geosynthetic mat is impregnated at the first point may be different from the liquid with which the geosynthetic mat is wetted at the installation site, that is, in particular, the composition may be different or additives that promote pre-expansion may be included. These additives, for example, promote pre-expansion but act to suppress or prevent biodegradation, and prevent premature biodegradation of the cover layer and connection structure due to impregnation at the first point.

[0063] And the geosynthetic mat is made transportable after impregnation at the first point, and in particular for this purpose it is preferably wound or folded into a roll and transported to the installation site. As a rule, in order to avoid the geosynthetic mat being impregnated differently at different locations, it is preferred to impregnate the geosynthetic mat uniformly at the first point in time before the geosynthetic mat becomes transportable.

[0064] The use according to the invention can be further developed in the use of a geosynthetic mat for producing a sealing layer on the bottom of a water area or in the use of a geosynthetic mat for producing a seal in a soil layer. The geosynthetic mat is laid on the bottom of the water area or installed in an area of the bottom of the water area or installed in the soil layer at the first point in time. The upper cover layer of the geosynthetic mat has an open porosity. As a further improvement, the outer surface of the upper cover layer has an outward roughness structure. The geosynthetic mat is installed in the soil layer. The upper cover layer of the geosynthetic mat has an open porosity. As a further improvement, the outer surface of the upper cover layer has an outward roughness structure. The geosynthetic mat is laid on the water floor such that the outer surface of the upper cover layer faces upward. Furthermore, the middle filler layer has a water permeability between 1×10 -5 and 1×10 -9 m / s. Particles entrained in the water area above the water area are deposited in the pore structure. Furthermore, it is affected by the reduction of the flow velocity and the reduction of the resistance force due to the roughness structure, moves from the upper cover layer to the middle filler layer, and particles from the water deposited in the middle filler layer and the upper cover layer form a sealing layer. At the second point in time, which is after the biological degradation of the upper cover layer, a supplementary sealing effect is formed in the expanded middle filler layer, and an additional sealing layer is formed at the site of the degraded upper cover layer.

[0065] According to this advantageous usage, the geosynthetic mat is used such that the center filler layer has a water permeability coefficient within a predetermined value range, thereby allowing the passage of liquid. This water permeability is combined with the porosity and thus the water permeability of the upper cover layer and preferably the lower cover layer, and is further improved by the outward roughness structure of the outer surface of the upper cover layer, which can be provided, for example, by the typical roughness of a non-woven layer or the regular structure of a cover layer made of a woven fabric, knitted fabric or warp knitted fabric. Thereby, in the initial stage after installation, the liquid flows through the center filler layer, and the particles in the liquid settle in the center filler layer and the top cover layer or the bottom cover layer, resulting in a decrease in permeability. Thus, due to the settlement of the liquid flowing through the geosynthetic mat and the accompanying particles, in the first stage after installation, the geosynthetic mat is gradually sealed, and then the water permeability coefficient continuously decreases, changing to a state where almost no flow occurs, and at this point, the geosynthetic mat is sealed. This sealing effect caused by the particles at the installation site in the initial stage is called cormation, and can be advantageously utilized for the overall characteristics, particularly due to the structure of the geosynthetic mat. By such a structure of the geosynthetic mat and the use of cormation, the middle filler layer does not need to expand so much, and acts with a high back pressure against the expansion behavior in the geosynthetic mat, so that the desired airtightness can be obtained only by this expansion behavior. Thereby, the requirements for the peel strength of the upper and lower cover layers and the connection structure are relaxed, and for example, by supplying an additive for increasing the shear strength of the middle filler layer to the middle filler layer, it is possible to design the middle filler layer to have only a limited expansion behavior. As a result, by the embodiments and usage according to the present invention, it is possible to provide a middle filler layer with increased shear strength, reduce the mechanical requirements for the upper and lower cover layers and the connection structure with respect to their biodegradation behavior and the resulting peel strength, and at the same time achieve a very low water permeability in the permanent use of the geosynthetic mat.

[0066] Before being laid on the bottom of the water area, the geosynthetic mat determines the amount of particles per volume of water carried into the water area as the particle amount density, and designs the geosynthetic mat so as to design the degree of expansion decomposition rate and / or the degree of residual peel strength and / or the thickness of the upper cover layer as a function of this particle amount density. Particularly preferably, the higher the particle amount density, the smaller the expansion decomposition rate is designed, the greater the degree of residual peel strength is designed, and / or the thickness of the upper cover layer is designed to be smaller. According to this embodiment, before installing the geosynthetic mat, the characteristics of the water area, particularly the amount of particles per volume of water in the water area, that is, the particle density in the water area, are determined. This includes the number of particles, but alternatively or additionally, also includes the size of the particles carried into the water area. Then, the geosynthetic mat is adapted according to this determined parameter of the water area related to the particle amount, whereby this adapted design achieves an ideal cormation effect and can be composed of adapting the characteristics of the upper cover layer and / or the characteristics of the middle filler layer in order to ideally adapt the geosynthetic mat thereto. For example, in a water area carrying particularly many particles, a middle filler layer with a lower degree of expansion can be used for the geosynthetic mat than in a water area having only a low particle density. The characteristics of the top cover layer can be similarly adapted. For example, in the case of a water area with a high particle density, rapid biodegradation with a significant decrease in peel strength accordingly can also be utilized. In this case, since a rapid sealing effect due to the cormation effect can be expected, the back pressure on the expansion of the middle filler layer does not play as large a role as in the case of a water area with a low particle concentration that requires such expansion behavior for the geosynthetic mat to exhibit a good sealing effect. Furthermore, the surface of the top layer can be adapted in terms of its roughness structure, and particles can be reliably deposited and embedded in the mat according to the flow conditions inherent in the water and the resistance of the mat surface.

[0067] A further aspect of the present invention is a method for manufacturing a geosynthetic mat, the method comprising the following steps: providing a first geosynthetic layer; applying a center filler layer of a filler layer material that has an expansion behavior and comprises an expandable material to the first geosynthetic layer; applying a second geosynthetic layer to the center filler layer; and connecting the first geosynthetic layer and the second geosynthetic layer, in particular by needling, through the center filler layer. A layer of a first biodegradable material is provided as the first geosynthetic layer, and a layer of a second biodegradable material is applied as the second geosynthetic layer. The upper cover layer and the lower cover layer have a mutual connection characterized by a peel strength as a result of adhesion. This connection is characterized by a residual peel strength formed by the square of the quotient of the reduced peel strength that the upper cover layer, the lower cover layer, and the connection structure have at a predetermined time after the start of the biodegradation process and the initial peel strength that the upper cover layer, the lower cover layer, and the connection structure have before the start of the biodegradation process. The residual peel strength is determined by a composting test in which the geosynthetic mat is completely placed in compost and composted for a predetermined time within a temperature range of 25°C or higher and 65°C or lower, and the peel strength is measured by a peel test at a predetermined time before and after removal from the compost. The expansion behavior is characterized by the degree of expansion lift formed by the quotient of the volume of the filler layer material containing water absorbed at a predetermined time and the initial volume of the filler layer material before the start of expansion. Here, the degree of expansion lift is determined by completely immersing the filler layer material layer in a water bath and applying a pressure of 4.5 N / m 2 to it. The expansion / degradation ratio, which is the value obtained by dividing the degree of expansion by the degree of residual peel strength, is in the range of 1 to 5 within the first week after the simultaneous start of the expansion process and the biodegradation process, and is in the range of 1.5 to 25, preferably in the range with a lower limit of 2 and an upper limit of 15, at each predetermined time from the beginning of the second month to the end of the third month after the start of expansion and degradation.

[0068] Regarding the manufacturing process, it should be understood that the characteristics of the geosynthetic mat regarding the degree of residual peel strength, the degree of swelling, and the resulting swelling / decomposition ratio over time, and its height can be achieved as described above for the geosynthetic mat.

[0069] Furthermore, by applying a structural material having a deterioration behavior corresponding to the deterioration behavior of the first or second cover layer or the third deterioration rate, and needling the structural material with a geosynthetic layer, a specific surface roughness structure can be manufactured. The method according to the present invention can be used in particular for manufacturing a geosynthetic mat having the above-described characteristics, and makes it possible to provide a geosynthetic mat suitable for the above-described use at the installation site.

[0070] It should be understood that the steps carried out by this method preferably bring about the above-described structural and functional characteristics and advantages of the geosynthetic mat according to the present invention and enable the above-described use. In this regard, reference is made to the previous description regarding the corresponding characteristics and advantages of these process steps.

[0071] The above-described method and further development of the method according to the present invention preferably further develop the first and / or second biodegradable materials in fiber form, in particular as fibers having a fiber core strand of the first biodegradable material and a fiber core strand sheath of the second biodegradable material, and the first biodegradable material has a first biodegradation rate higher than the second biodegradation rate of the second biodegradable material. According to a further development of this process, the first and / or second biodegradable materials are formed from fibers having a two-layer structure, i.e., fibers having a fiber core strand and a fiber core strand sheath, where the fiber core strand sheath may already exist before the respective layers or connection structures are manufactured from the fibers, or may be applied later in the manufacturing process, or may be applied only on-site at the installation location. In this regard, reference is made to the previous description of the corresponding fibers used in the geosynthetic mat or the corresponding geosynthetic sheet according to the present invention.

[0072] This process can be further developed by manufacturing the first and / or second top layers from the fiber core strands in a first process and subsequently coating the fiber core strands in the first and / or second top layers with a fiber core strand sheath in a second process. According to this embodiment, the fiber core strand sheath is applied only after the top layer has been manufactured from the fiber core strands, thereby achieving a comprehensive coating of the fiber core strands including any end cut edges. For this also, refer to the previous description.

[0073] It is further preferred that the entire top cover layer and / or bottom cover layer, center filler layer, or geosynthetic mat is impregnated with a liquid, particularly a hardening liquid such as hard oil. This manufacturing step of impregnating with a liquid such as hard oil can be carried out directly during the manufacture of the geosynthetic mat at the manufacturing site, but can also be carried out immediately before the geosynthetic mat is transported to the installation site or after the geosynthetic mat has been transported to the installation site, for example, when the geosynthetic mat has already been laid. The advantages of delayed impregnation with the liquid described above also apply to the method according to the present invention in this regard.

[0074] Also, when applying the center filler layer, it is preferable to also apply a non-expansive aggregate, particularly sand. By using a non-expansive aggregate, the expansion behavior of the middle filler layer is affected, for example, promoting the corrugation effect, increasing the shear strength of the middle filler layer, thereby improving the installation suitability of the geosynthetic mat in an installation situation where it is subjected to a shear load such as on a slope, which is particularly advantageous after the connection structure with the upper and lower cover layers has decomposed.

Brief Description of the Drawings

[0075] Preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0076]

Figure 1

Figure 2a

Figure 3a

Figure 4a

Figure 5

Mode for Carrying Out the Invention

[0077] First, referring to Figure 1, a preferred embodiment of the geosynthetic mat according to the present invention is composed of a total of five layers. The uppermost layer is a first sealing layer 10 made of biodegradable plastic as a liquid-tight film, which covers the upper surface of the geosynthetic mat as a fluid barrier.

[0078] The upper cover layer in the form of a non-woven fabric layer 20 is disposed adjacent below this upper sealing layer 10. This non-woven fabric layer is composed of randomly laid fibers and usually has a thickness greater than that of the sealing layer 10, particularly a thickness three to ten times that of the sealing layer 10.

[0079] The middle filler layer in the form of a layered silicate layer of sodium bentonite is disposed adjacent and below the upper top layer 20. The thickness of this middle filler layer 30 is greater than the thickness of the nonwoven layer 20, typically 5 to 20 times greater than the thickness of the nonwoven layer 20. This middle filler layer contains a mixture of sodium bentonite particles and sand particles and can be impregnated with, for example, linseed oil depending on the application. With this composition, the middle filler layer initially exhibits basic strength and groundwater impermeability and can further enhance this strength and impermeability by swelling the sodium bentonite in the composition with ambient moisture such as soil moisture. During this swelling process, the sodium bentonite changes to calcium bentonite and the middle filler layer solidifies. The middle filler layer can also be configured in another way, in which case it should be understood that it also has an initial base strength and an initial base density that can be increased by swelling due to ambient moisture. For example, the center filler layer can be composed of only swelling materials such as bentonite or layered silicate, or aggregates other than sand can be used. The impregnation with linseed oil can be replaced or supplemented with other liquids such as hard oil, or such impregnation can be omitted.

[0080] A second sealing layer 40 is disposed under the center filling layer 30, which is designed in the same way as the first sealing layer 10. The first sealing layer 10 and the second sealing layer 40 prevent swelling promoters and swelling inhibitors from entering the middle filler layer from the surrounding soil layer immediately after the construction of the geosynthetic mat, which may have an adverse effect on the swelling behavior.

[0081] Finally, a geotextile layer 50 containing woven fibers is disposed adjacent and below the second sealing layer 40. In this way, the fibers of the geotextile layer 50 are neatly arranged, in this case in a rectangular grid pattern, ensuring good longitudinal and transverse load-bearing properties of the geosynthetic mat.

[0082] The entire geosynthetic mat is fixed to each other by the needling 11 in the thickness direction, that is, the direction perpendicular to the elongation in the longitudinal and transverse directions. The needling fixation includes a number of individual needling points, which are distributed throughout the geosynthetic mat and can be arranged, for example, in rows and columns or pseudo-randomly relative to each other. This needling connects the upper cover layer and the lower cover layer over a large area, and the composite of the upper cover layer and the lower cover layer and the needling thus has resistance to the peeling of the upper cover layer or the lower cover layer from the composite, that is, the peel strength.

[0083] The needling can be achieved by piercing a barbed needle perpendicularly into the geosynthetic mat, thereby extracting fibers from the nonwoven layer 20 and / or the geotextile layer 50 and pulling these fibers vertically through the geosynthetic mat. These fibers are intertwined in the geotextile layer 50 and the nonwoven layer and also in the sealing layers 10, 40. Such intertwining and looping can be further strengthened by welding or knotting to enhance the fixation by the needle. Instead of such needling, other methods can also be used to fix the layers of the geosynthetic mat to each other, for example, sewing with fibers in the same pattern as the needling, thereby passing the sewing thread vertically through the geosynthetic mat at multiple points, thereby fixing and stabilizing the layers to each other, and the geosynthetic mat can be sewn. When used in water channels and water areas including the corrugation effect, layer 10 can be replaced with a surface roughness structure and layer 40 can be omitted to obtain the initial flow.

[0084] It should be understood that the geosynthetic mat extends in the longitudinal direction LR and the transverse direction QR and can be wound up especially along the longitudinal direction LR. The ends of the geosynthetic mat can be sealed such that, when viewed in the transverse direction, the first sealing layer 10 and the non-woven fabric layer 20, and the lower sealing layer 40 and the fabric layer 50 project transversely beyond the center filler layer, and these projecting portions are stitched together so as to also surround the center filler layer transversely.

[0085] Figure 2 shows a second embodiment of the geosynthetic mat according to the present invention in a cross-sectional longitudinal view. Here too, the center filler layer 130 is disposed at the center. The first sealing layer 110 and the second sealing layer 140 are disposed above and below, respectively, adjacent to this center filler layer, in contrast to the first embodiment of FIG. 1, and as a result, are disposed directly adjacent to the center filler layer. And the non-woven fabric layer 120 is disposed above the first sealing layer as an upper cover layer, and the fabric layer 150 is disposed below the second sealing layer 140 as a lower cover layer. Also in this case, the individual layers of the geosynthetic mat are fixed to each other by needling 111 and are fixed. Further, it can be seen that the upper cover layer, the first sealing layer, the second sealing layer, and the lower cover layer project transversely and are stitched or needled along the side edges to seal the center filler layer transversely as well.

[0086] Figure 3 shows fibers that can form a connection structure as, for example, the needling 11, nonwoven layers 20, 120 or woven layers 50, 150, or can be included in such layers. The fiber comprises a fiber core strand 210 made of a first biodegradable material. Around the fiber core strand, a fiber core strand sheath 220 is arranged as a cylindrical sheath containing a second biodegradable material. The first biodegradable material has a higher strength and a faster biodegradation rate than the second biodegradable material. When the fiber composed of such two layers undergoes the biodegradation process and at the same time has to absorb mechanical loads over a limited period, the mechanical load capacity of this fiber will proceed advantageously. In this process, the mechanical load resistance initially either decreases slightly or does not decrease at all. This is because only the coating of the fiber core strand biodegrades and does not contribute significantly to the mechanical properties. Only after the deterioration of the fiber core strand sheath 220 does the fiber core strand 210 also deteriorate, and the mechanical strength of this fiber rapidly decreases.

[0087] Figure 4 is a longitudinal side view of a short fiber or medium fiber according to the present invention. This fiber also comprises a fiber core strand 310 coated by a fiber core strand sheath 320. In terms of mechanical properties and biodegradation rate, the fiber core strand and the fiber core strand sheath 310, 320 are designed in the same way as the embodiment described above according to Figure 3. As can be seen from Figure 4, the fiber core strand sheath 320 coats the fiber core strand 310 on all sides, that is, also on the end faces. This is achieved by applying the fiber core strand sheath only after the fiber core strand 310 has been processed and cut to size, thereby achieving a coating that is advantageous for the biological and mechanical degradation behavior over the entire surface.

[0088] FIG. 5 schematically shows the course of the peel strength S(t) of a composite of two needle nonwoven layers, which is composed of fibers according to FIG. 3 or FIG. 4 and thus contains fibers having a fiber core strand and a sheath of the fiber core strand, or is composed of a sheath of the fiber core strand. As can be seen from the course of this curve, the curve initially only decreases slightly over a certain period, resulting in only a slight decrease in tensile strength. Only at the time point t when the sheath of the fiber core strand is almost completely biodegradable does the peel strength of the composite decrease more steeply. This is because from this time point t, the fiber core strand biodegrades, and as a result, the peel strength of the fibers, which is greatly affected by this, decreases. In the example of this embodiment, the overall peel strength of the composite is affected by the biodegradation of the fibers in the upper and lower cover layers and the connection structure, i.e., the needling. For example, when a non-biodegradable connection structure connects two cover layers, one or both of which are biodegradable, for example, as can be achieved by stitching. In this case, the peel strength is only affected by the fixing strength of the connection structure of the biodegradable top layer.

[0089] FIG. 5 also shows the swelling behavior of the medium fill layer in the form of a curve Q(t) as the degree of swelling of the medium fill layer. As can be seen, after an initial short delay, the center filler layer first rapidly increases in volume, which corresponds to the initial rapid swelling, and then changes to a slow increase in volume corresponding to the slow swelling, and then asymptotically approaches the final swollen state.

[0090] From FIG. 5, a layer made of fibers showing peel strength behavior according to S(t) is used as the upper and lower cover layers, and a geosynthetic mat in which such fibers are needled has a middle filler layer showing expansion behavior according to Q(t). At an important part of the expansion of the middle filler layer, it still shows a high peel strength and has a high peel strength at an important part of the expansion of the middle filler layer. Therefore, it can be seen that it can withstand the inflation pressure with a sufficiently high back pressure to achieve a desirable good homogenization and removal of air voids in the middle filler layer as a result of inflation. The biodegradable fibers of the top and bottom cover layers and needling have almost completed inflation, and only the volume and weight of the middle filler layer increase slightly due to residual inflation. Then, it is in a stage of rapid biodegradation, and as a result, the peel strength rapidly decreases, that is, the peel strength decreases highly. At this point, there is no need to apply a large back pressure to prevent inflation. Instead, the geosynthetic mat benefits from the fact that the middle filler layer expands well and is sealed.

[0091] The calculation of the source degradation rate will be described in detail using the following four examples:

[0092] 1) The expansion volume of the middle filler layer in the inflation lift test with a load of 45 Pa is 40 liters after one week of inflation and 50 liters after three months. The volume before inflation started was 20 liters. As a result, the volume doubled within one week, the degree of expansion became 2, and after three months, the degree of expansion became 2.5. The peel strength at the start of the composting test was 120 N / 10 cm, and it hardly changed in the first week. The peel strength after three months of composting was 90 N / 10 cm. As a result, the peel strength after three months decreased by 25%, and the residual peel strength became 0.56. As a result, the inflation and decomposition rate after one week was 2, and the inflation and decomposition rate after two or three months was 4.4.

[0093] 2) In the expansion and contraction test with a load of 45 Pa applied, the expansion volume of the middle filler layer was 60 liters after 1 week of expansion and 80 liters after 3 months, and then it hardly increased any further. The volume before the start of expansion was 20 liters. As a result, the volume tripled within 1 week, reaching an expansion degree of 3, and after 3 months or more, the expansion degree became 4. The peel strength at the start of the composting test was 120 N / 10 cm, but it decreased to 115 N / 10 cm within 1 week, and the peel strength after 3 months of composting was 60 N / 10 cm, and decreased to 40 N / 10 cm at the 12th month. As a result, it decreased by approximately 4% in the first week, resulting in a residual peel strength of 0.96, decreased by 50% after 3 months, resulting in a residual peel strength of 0.25, and a residual peel strength of 0.1 after 12 months. As a result, the expansion / deterioration ratio increased to 3.1 after 1 week, 16 after 3 months, and 36 after 12 months.

[0094] 3) In the expansion and contraction test with a load of 45 Pa applied, the expansion volume of the middle filler layer was 30 liters after 1 week of expansion, 40 liters after 3 months, and still 40 liters after 12 months. The volume before the start of expansion was 20 liters. As a result, the expansion degree was 1.5 after 1 week, and 2 after 3 months and 12 months. The peel strength at the start of the composting test was 120 N / 10 cm, which hardly changed in the first week. The peel strength after 3 months of composting was 90 N / 10 cm, and decreased to 60 N / 10 cm at the 12th month. As a result, the residual peel strength after 3 months was 0.56, and the residual peel strength after 12 months was 0.25. As a result, the expansion / deterioration ratio was 1.5 after 1 week, increased to 3.6 after 3 months, and up to 8 after 12 months.

[0095] 4) In the expansion and settlement test with a load of 45 Pa, the expansion volume of the middle filler layer was 40 liters after 1 week of expansion, 60 liters after 3 months, and 80 liters after 12 months. The volume before the start of expansion was 20 liters. As a result, the degree of expansion after 1 week was 2, after 3 months was 3, and after 12 months was 4. The peel strength at the start of the composting test was 120 N / 10 cm, but it decreased to 110 N / 10 cm within 1 week, the peel strength after 3 months of composting was 40 N / 10 cm, and it decreased to 20 N / 10 cm at the 12th month. As a result, the residual peel strength after 1 week was 0.84, after 3 months was 0.11, and after 12 months was 0.03. As a result, the expansion / deterioration ratio after 1 week was 2.4, increased to 27 after 3 months, and increased to 133 after 12 months.

[0096] Therefore, in this example, Examples 1, 2, and 3 represent geosynthetic mats that have particularly favorable properties according to the present invention and achieve good sealing behavior. The geosynthetic mat according to Example 4 shows rapid expansion behavior with respect to rapid biodegradation and the accompanying loss of peel strength. This geosynthetic mat according to the present invention can achieve good sealing behavior even under heavy loads from the soil layer above it, but it is not very suitable when there is no heavy load to compensate for the rapid biodegradation because the counter-expansion pressure for achieving good sealing is too low.

Claims

1. A geosynthetic mat, comprising: - an upper top layer; - a lower top layer; - a filler layer material disposed between a top cover layer and a bottom cover layer and composed of an expandable material-containing filler layer material, the filler layer material comprising a middle filler layer having an expansion behavior; - a connection structure in which the top cover layer and the bottom cover layer are mechanically connected to each other at a plurality of positions via a center filler layer, the connection positions being spaced apart from each other, preferably arranged at a certain distance from each other along a straight line, whereby the top cover layer and the bottom cover layer have a peel strength with respect to each other via the connection structure; The top cover layer and / or the bottom cover layer is characterized by containing a biodegradable material or being composed of a biodegradable material; The peel strength at a predetermined time after the start of the biodegradation process is characterized by the degree of residual peel strength formed by the square of the quotient of the reduced peel strength of the upper and lower cover layers and the connection structure at the predetermined time and the initial peel strength of the upper and lower cover layers and the connection structure before the start of the biodegradation process, and the degree of residual peel strength is - a composting test by completely putting the geosynthetic mat into compost, composting it for a predetermined time in a temperature range of 25°C or higher and 65°C or lower, and measuring the peel strength by a peel test at a predetermined time before putting it in and after taking it out of the compost, or - a marine incubation test by measuring the peel strength by a peel test at a predetermined time before insertion and after taking it out of seawater under aerobic conditions in seawater having a temperature of 30°C ± 2°C and a salt concentration of 3.5 wt% ± 1 wt%; determined by - The expansion behavior is characterized by the degree of expansion lift formed by the quotient of the volume of the filler layer material containing the water absorbed at a predetermined time point and the initial volume of the filler layer material before the start of expansion. The degree of expansion lift is determined by completely immersing the layer of the filler layer material in a water bath and applying a pressure of 4.5 N / m ２ to the layer of the filler layer material, The expansion / degradation ratio, which is the value obtained by dividing the degree of expansion by the degree of residual peel strength, is in the range of 1 to 5 within the first week after the simultaneous start of the expansion process and the biodegradation process, and in the range of 1.5 to 25, preferably with a lower limit of 2 and an upper limit of 15, from the beginning of the second month to the end of the third month after the start of expansion and degradation, for the geosynthetic mat.

2. The geosynthetic mat according to claim 1, characterized in that the expansion / degradation ratio from the third month to the end of the twelfth month after the start of the expansion process and the biodegradation process is in the range of 2 to 50, preferably with a lower limit of 3 and / or an upper limit of 30.

3. A geosynthetic mat according to any one of the preceding claims, - the degree of swelling being greater than 1.25 one week after the start of the swelling process, and / or - the degree of swelling being greater than 1.5 one month after the start of the swelling process, and / or - the degree of residual peel strength three months after the start of the swelling process being less than 0.95, and / or - the degree of residual peel strength twelve months after the start of the swelling process being less than 0.75, the geosynthetic mat.

4. A geosynthetic mat according to any one of the preceding claims, characterized in that the connection structure comprises or is formed by needling between the upper and lower cover layers, the geosynthetic mat.

5. A geosynthetic mat according to any one of the preceding claims, characterized in that the upper and / or lower cover layer and / or connection structure comprises or is formed by fibers of a biodegradable material, the geosynthetic mat.

6. A geosynthetic mat according to any one of the preceding claims, - the biodegradable materials of the top cover layer and the bottom cover layer being different from each other, or - the biodegradable material of the top cover layer being the same as the biodegradable material of the bottom cover layer, characterized in that, the geosynthetic mat.

7. A geosynthetic mat according to any one of the preceding claims, - the biodegradable material of the connection structure being different from the biodegradable material of the top cover layer and / or the bottom cover layer, or - the biodegradable material of the connection structure being the same as the top cover layer or the bottom cover layer, characterized in that, the geosynthetic mat.

8. A geosynthetic mat according to any one of the preceding claims, characterized in that the upper cover layer and / or the lower cover layer comprises or is formed by a non-woven layer of a biodegradable material, the geosynthetic mat.

9. A geosynthetic mat according to any one of the preceding claims, The geosynthetic mat is characterized in that the upper cover layer and / or the lower cover layer comprises or is formed by a regular fabric layer, in particular a knitted, woven or crocheted fabric layer of biodegradable material. **Claim 10** A geosynthetic mat according to any of the preceding claims, characterized in that the filler layer material comprises or is formed by a mixture of an expandable material such as bentonite powder, in particular sodium bentonite, and a non-expandable aggregate such as an inorganic bulk material, in particular sand, glass granules, chalk or coal granules. **Claim 11** A geosynthetic mat according to any of the preceding claims, characterized in that the filler layer comprises a curable liquid or a liquid that causes hardening, in particular a hard oil or wax or varnish based on, for example, linseed oil or tung oil, and it is also possible for the liquid to be present only in a partial area such as a partial cross-section of the filler layer. **Claim 12** A geosynthetic mat according to any of the preceding claims, characterized by an upper barrier layer disposed adjacent to the upper cover layer and / or a lower barrier layer disposed adjacent to the lower cover layer, each barrier layer being formed by a film, in particular a film made of biodegradable material, preferably - an upper barrier layer between the upper top layer and the center filler layer, - a bottom barrier layer between the bottom top layer and the center filler layer, - an upper top layer between the upper barrier layer and the center filler layer, or - a bottom top layer between the bottom barrier layer and the center filler layer is disposed. **Claim 13** A geosynthetic mat according to any of the preceding claims, wherein the biodegradable material of each barrier layer is - the same as or - different from the biodegradable material of the top cover layer or bottom cover layer adjacent to the film. **Claim 14** A geosynthetic mat according to any of the preceding claims, The biodegradable material of the top cover layer, bottom cover layer and / or connection structure comprises fibers or is composed of fibers having a fiber core strand of a first biodegradable material and a fiber core strand sheath of a second biodegradable material covering the fiber core strand, and the first biodegradable material has a first biodegradation rate higher than the second biodegradation rate of the second biodegradable material, characterized in that it is a geosynthetic mat.

15. The geosynthetic mat according to any one of the preceding claims, wherein the first biodegradable material comprises natural fibers such as coconut fiber, jute fiber, hemp fiber, bamboo fiber, linen fiber, or biodegradable synthetic fibers of PBS, PBAT, PLA, or a polymer mixture of at least two of these materials, or is composed of them, or the biodegradable material comprises a mixture of fiber cores of natural fibers and synthetic fibers, and the weight ratio of the synthetic fibers preferably exceeds 30%, particularly exceeds 50%, characterized in that it is a geosynthetic mat.

16. The geosynthetic mat according to any one of the preceding claims, wherein the second biodegradable material comprises a biodegradable polyester such as a cellulose-based plastic, starch mixture, lyocell, succinic acid (PBS), polybutyrate adipate terephthalate (PBAT) or polylactic acid (PLA), or wax, or is composed of them, characterized in that it is a geosynthetic mat.

17. The geosynthetic mat according to any one of the preceding claims, The middle filler layer has a permeability of 1×10 －５ to 1×10 －９ m / s, and is a geosynthetic mat characterized by this.

18. A geosynthetic sheet comprising at least one layer comprising fibers or formed by fibers, wherein the fibers comprise a fiber core strand of a first biodegradable material and a fiber core strand sheath of a second biodegradable material covering the fiber core strand, the first biodegradable material has a first biodegradation rate, and the second biodegradable material has a second biodegradation rate different from the first biodegradation rate of the first biodegradable material, particularly higher than the first biodegradation rate of the first biodegradable material, characterized in that it is a geosynthetic mat.

19. The geosynthetic sheet according to claim 17, wherein the fibers in the layer are ・Particularly available as an irregular structure as a fleece layer, or ・ A geosynthetic sheet, characterized in that it can be used as a regular structure, particularly as a knitted, woven, or crocheted fabric layer.

20. The geosynthetic sheet according to claim 18 or 19, wherein the circumferential and end faces of the fibers are coated with a fiber core strand coating, and in particular, in a first step, the fiber core layer is manufactured from fiber core strands, and in a subsequent second step, the fiber core strands of the fiber core layer are coated with a coating material, and the layered layer is manufactured by a process in which the fiber core strands of the fiber core layer are coated with a coating material. A geosynthetic sheet characterized by being manufactured.

21. A geosynthetic mat according to any one of claims 1 to 17, wherein the upper cover layer and / or the lower cover layer comprises a geosynthetic sheet according to any one of claims 18, 19 or 20, or is formed by such a geosynthetic sheet. A geosynthetic mat characterized by being formed.

22. Use of a geosynthetic mat according to any one of claims 1 to 21 for producing a sealing layer on the ground or the bottom of a water area.

23. The use according to claim 22, characterized in that in a first step, the geosynthetic mat is unrolled, and in a subsequent second step, the geosynthetic mat is impregnated with a liquid, particularly oil, preferably hard oil, resin, or a varnish based thereon. Use.

24. The use according to claim 22 or 23, wherein the geosynthetic mat is impregnated with a liquid at a first point before laying, causing partial pre-expansion of the middle filler layer, and then installed at the installation position at a second point, and in particular expands at the installation position by the supply of liquid from the surrounding soil. A use characterized by being.

25. The use according to claim 25, characterized in that the geosynthetic mat becomes transportable after the first point, and in particular is rolled up and transported to the installation site. Use.

26. Use according to any one of claims 22 to 25 for forming a sealing layer on the bottom of a water area, characterized in that the geosynthetic mat is laid on the bottom of the water area, The upper cover layer of the geosynthetic mat has a porosity, the outer surface of the upper cover layer has an outward roughness structure, and the geosynthetic mat is laid on the bottom of the water area so that the outer surface of the upper cover layer faces upward. The middle filler layer has a permeability of 1×10 －５ to 1×10 －９ m / s, particles carried to the water area above the water area are entangled in the roughness structure, move through the upper cover layer to the middle filler layer, and as a result, particles from the water area deposited in the middle filler layer and the upper cover layer form a sealing layer, and at the second point after the biodegradation of the top cover layer, a supplementary sealing effect is formed in the expanded center filler layer, and an additional sealing layer is formed at the site where the top cover layer has decomposed.

27. The use according to claim 26, before laying the geosynthetic mat on the bottom of the water area, determining the amount per volume of the particles carried into the water area as the particle amount density, and designing the geosynthetic mat such that the expansion - decomposition ratio, and / or the degree of residual peel strength, and / or the thickness of the upper cover layer is designed as a function of this particle amount density. In particular, the higher the particle amount density, the larger the expansion - decomposition ratio is designed, the smaller the degree of residual peel strength is designed, and / or the smaller the thickness of the upper cover layer is designed.

28. A method for manufacturing a geosynthetic mat, - a step of preparing a first geosynthetic layer, - applying a middle filler layer of a filler layer material containing an expandable material to the first geosynthetic layer, the filler layer material having an expansion behavior, - spreading a second geosynthetic layer over the center filler layer, - connecting the first geosynthetic layer and the second geosynthetic layer through the center filler layer, in particular, by a connecting structure by needling, characterized in that a layer of a first biodegradable material is provided as the first geosynthetic layer and a layer of a second biodegradable material is applied as the second geosynthetic layer. The upper cover layer and the lower cover layer have a mutual connection characterized by the peel strength as a result of adhesion. This connection is formed by the square of the quotient of the reduced peel strength of the upper cover layer and the lower cover layer and the connection structure at a predetermined time after the start of the biodegradation process and the initial peel strength of the upper cover layer and the lower cover layer and the connection structure before the start of the biodegradation process, and the degree of residual peel strength. The degree of residual peel strength is determined by a composting test in which the geosynthetic mat is completely placed in compost, composted for a predetermined time in a temperature range of 25 °C or higher and 65 °C or lower, and the peel strength is measured by a peel test at a predetermined time before and after taking it out of the compost. The expansion behavior is characterized by the degree of expansion lift formed by the quotient of the volume of the filler layer material containing the water absorbed at a given time point and the initial volume of the filler layer material before the start of expansion, where the degree of expansion lift is determined by completely immersing the filler layer material layer in a water bath and applying a pressure of 4.5 N / m ２ to the filler layer material layer, The expansion / decomposition ratio, which is the value obtained by dividing the degree of expansion by the degree of residual peel strength, is in the range of 1 to 5 within the first week after the simultaneous start of the expansion process and the biodegradation process, and is in the range of 1.5 to 25, preferably with a lower limit of 2 and an upper limit of 15, at each predetermined time point from the beginning of the second month to the end of the third month after the start of expansion and decomposition. A method for manufacturing a geosynthetic mat.

29. A method according to claim 28 or the generic term of claim 28, wherein a layer of a first biodegradable material is provided as a first geosynthetic layer, and a layer of a second biodegradable material is applied as a second geosynthetic layer, and the first biodegradable material and / or the second biodegradable material is in the form of fibers, in particular in the form of fibers having a fiber core strand of the first biodegradable material and a sheath of the fiber core strand of the second biodegradable material, and the first biodegradable material has a first biodegradation rate higher than the second biodegradation rate of the second biodegradable material. A method.

30. A method according to claim 29, wherein the first cover layer and / or the second cover layer is manufactured from fiber core strands in a first step, and in a subsequent second step, the fiber core strands in the first cover layer and / or the second cover layer are covered with a fiber core strand sheath. A method.

31. A method according to any one of claims 29 to 30, wherein the upper and / or lower top layer, the middle filler layer, or the entire geosynthetic mat is impregnated with a liquid, particularly preferably a water-repellent liquid such as oil, preferably a curable water-repellent liquid such as hard oil, or a varnish based thereon. A method.

32. A method according to any one of claims 29 to 31, wherein a non-expansive aggregate, particularly sand, is additionally applied during the application of the middle filler layer. A method.

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