Biodegradable ground sealing sheet

Abstract

The invention relates to a plastics geo-mat, comprising an upper cover layer, a lower cover layer, and a middle filling layer, which is disposed between the upper cover layer and the lower cover layer and is composed of a filling layer material comprising a material capable of swelling. The invention is characterized in that the upper cover layer and / or the lower cover layer consists of or comprises a biodegradable material; the peeling resistance at a predefined time after the start of the biodegradation process is characterized by a residual degree of peeling resistance, which is formed by the square of a quotient of a reduced peeling resistance which the upper and lower cover layers and the connecting structure have at the predefined time and an initial peeling resistance which the upper and lower cover layers and the connecting structure have before the start of a biodegradation process.

Description

[0001] Biodegradable soil sealing membrane

[0002] The invention relates to a geosynthetic mat comprising an upper cover layer, a lower cover layer, a middle filler layer arranged between the upper cover layer and the lower cover layer and made of a filler layer material which comprises a swellable material, wherein the filler layer material has a swelling behavior, and a connecting structure by means of which the upper and lower cover layers are mechanically connected to one another at several positions through the middle filler layer, wherein the positions of the connection are spaced from one another, preferably at a regular distance from one another along positions following straight lines, so that the upper and lower cover layers have a peel strength to one another due to the connecting structure.

[0003] The fill layer material exhibits a swelling behavior that is typically characterized at a predetermined time after the start of the swelling process by a degree of swelling, which is determined by the ratio of the volume of the fill layer material, including the water absorbed therein, at the predetermined time to an initial volume of the fill layer material that the fill layer material had before the start of the swelling process. The degree of swelling is determined by completely immersing the geosynthetic mat in a water bath for a period up to the predetermined time and determining the volume of the fill layer material before immersion and at the predetermined time. The degree of swelling therefore indicates the swelling capacity of a material under unhindered conditions and can be determined, for example, according to ASTM D5890.For example, a defined amount (2g) of dry fill layer material is placed into a 100ml measuring cylinder filled with 90ml of water. The cylinder is then filled with water up to 100ml. The fill layer material sinks to the bottom, and immediately after the filling material has been added, the initial volume of the fill layer material can be read off the scale on the measuring cylinder. The fill layer material then swells for a predetermined period of time, for example, at least 16 hours. The swelling volume can then be read off by determining the height of the swollen fill 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.

[0004] A further aspect of the invention is a use of such a geosynthetic mat and a method for producing such a geosynthetic mat.

[0005] Geosynthetic mats of the aforementioned type are used to create a waterproofing layer on or within a soil layer. In other applications, such geosynthetic mats can also be used to additionally stabilize a soil layer and / or protect a structure against mechanical or hydraulic impacts or combinations thereof, for example, in the area of ​​a riverbank or channel bank, an embankment, a dam, or a dike structure. They can also be used to protect other thin-layer waterproofing components.

[0006] The functional principle of such geosynthetic mats is that the middle fill layer, which is typically many times thicker than the upper and lower cover layers, is neither swollen nor hardened immediately after production, thus exhibiting a mechanical flexibility that allows the geosynthetic mat to be rolled up into a roll. This makes the geosynthetic mat transportable, while also allowing it to conform to the soil topology at the installation site. At the installation site, the geosynthetic mat is then rolled out; if necessary, by rolling out several geosynthetic mats in parallel and overlapping order, a soil area can be covered that is wider than the width of the geosynthetic mat transversely to its longitudinal direction, which corresponds to the unrolling direction.

[0007] After installation, the middle fill layer swells due to water absorption, which can be caused by soil moisture at the installation site and, if necessary, accelerated by artificial water supply. This swelling causes homogenization and a reduction in the air pore volume of the middle fill layer, whereby it achieves the desired homogeneous and largely isotropic, very low water permeability, characterized by the permeability value kio, which, after swelling of the middle fill layer, is ideally less than 5x10 -10 and preferably smaller than 5x10 -11m / s. However, this homogenization and reduction in air void volume requires that the middle fill layer cannot expand unhindered, which requires the influence of the interconnected upper and lower cover layers as mechanical counterpressure, thereby achieving a desired limitation of the volume increase. In certain installation situations or installation phases, such counterpressure can also be caused or increased by surface pressure on the upper cover layer, which is achieved by installing soil layers above the geosynthetic mat via their weight. The achieved low water permeability creates a sufficiently high sealing effect to be able to retain water in standing or flowing waters, provide landfill sealing or protect dykes against moisture penetration.

[0008] The upper and lower cover layers and the connecting structure connecting these two cover layers therefore fulfill essential functions that are necessary for the use and properties of the geosynthetic mat. The cover layers and the connecting structure make the geosynthetic mat rollable and easy to handle. Consequently, they retain their structure, with the middle fill layer positioned between the two cover layers at a desired thickness, even when rolled up after production, during transport, and during installation at the installation site. Furthermore, the two cover layers and the connecting structure create and maintain mechanical stabilization and therefore mechanical counterpressure against the swelling pressure of the middle fill layer after the geosynthetic mat has been installed, causing the middle fill layer to develop a desired, dense structure upon swelling.According to the inventors' findings, this swelling under the mechanical counterpressure, which is achieved by constricting the middle fill layer between the two cover layers and the connecting structure, means that the desired low permeability of the geosynthetic mat can only be achieved after the middle fill layer has swelled. This low permeability should ideally be achieved regardless of whether or not a layer with a certain weight can be installed above the geosynthetic mat. Finally, in installation situations where a geosynthetic mat of the aforementioned type is installed at an angle, for example on a slope, the geosynthetic mat must have a shear strength to prevent the geosynthetic mat itself from constituting or forming an unstable layer in the slope, which could lead to slope sliding with the geosynthetic mat as the separating layer.This shear strength is achieved by the connection structure between the upper and lower cover layers, which creates a stable connection between the lower soil layer on which the lower cover layer rests and the upper soil layer resting on the upper cover layer.

[0009] Geosynthetic mats of the above-mentioned type with properties that provide good sealing, shear strength and mechanical resilience are known as clay sealing membranes, such as the bentonite mat from Naue GmbH & Co. KG, and are described in EP 0 278 419 B1.

[0010] DE19956783A1 discloses a mat designed for covering carcasses, which was developed from the bentonite mat described in EP 0278419 B1. This modified mat uses a virucidal or bactericidal powder instead of the sealing powder (e.g., bentonite) to create a mat that effectively prevents the emergence of active microorganisms from the burial site through a chemical-biological effect. The mat thus developed takes a path of providing a chemical-biological barrier against microorganisms, instead of sealing by swelling, by using appropriate virucidal / bactericidal fillers. This represents a special mat suitable for the specific purpose of covering carcasses and the associated microbial hazard, but it is not well suited for other purposes.

[0011] DE60203517T2 discloses another floor mat based on the technology known from EP0278419B1. The aim of this floor mat is to ensure that the bentonite arranged in the intermediate layer can penetrate into the cavities and gaps in the adjacent soil area and only swells there. This should fill these cavities and gaps. To achieve this, the top layer of the floor mat is designed to dissolve upon contact with the soil due to the influence of water. The technology of this floor mat therefore departs from the principle of the floor mat originally described in EP0278419B1, with a swelling and compaction function of the bentonite within the intermediate layer, and instead aims for rapid dissolution of the top layer so that the bentonite can move from the intermediate layer into the cavities and gaps in the adjacent soil before it begins to expand and then swell there.This ground mat is therefore suitable for special applications where a soil layer composed primarily of waterproofing earth materials, but containing hollow spaces, needs to be sealed by sealing these defects. Due to the rapid disintegration of the top layer required for this, it is not suitable for other general waterproofing applications.

[0012] Such previously known geosynthetic mats are installed for temporary or permanent sealing, for example, to protect thin-layer plastic films, as an element with a separating function, or to stabilize soil layers or surfaces. However, in some applications with morphologically variable geometries, adverse long-term effects from an environmental protection perspective arise. For example, with the permanent use of such geosynthetic mats, sections of the geosynthetic mat can be severed by erosion processes and transported to other locations by wind or water currents, then causing contamination at an undesirable location. With the temporary use of such geosynthetic mats, the geosynthetic mat can, in some cases, be removed from the soil in isolation and then disposed of.In many cases, however, such isolated removal is not possible because layers of soil adhere to the geosynthetic mat or the geosynthetic mat is damaged during removal. In such cases, a large amount of soil is often removed, and the entire removed volume must then be disposed of. Due to the synthetic components in this removed volume, disposal falls into high pollutant classes and is correspondingly costly.

[0013] The invention is based on the object of providing a geosynthetic mat which overcomes these aforementioned disadvantages and at least maintains, and preferably exceeds, the necessary mechanical properties and sealing properties of previously known geosynthetic mats.

[0014] This object is achieved according to the invention with a geosynthetic mat of the type mentioned at the outset, in which the upper cover layer and / or the lower cover layer consist of a biodegradable material or comprise a biodegradable material, wherein the peel strength at a predetermined time after the start of the biodegradation process is characterized by a residual peel strength degree which is formed by the square of a quotient of a reduced peel strength which the upper and lower cover layers and the connecting structure have at the predetermined time to an initial peel strength which the upper and lower cover layers and the connecting structure have before the start of a biodegradation process, wherein the residual peel strength degree is determined in a composting test by completely immersing the geosynthetic mat in compost and composting in a temperature range which is above 25°C and below 65°C,up to the predetermined time and measuring the peel strength in a peel test before insertion and at the predetermined time after removal from the compost or in a marine incubation test, with the following ambient conditions:; temperature 30°C + / - 2°C; aerobic conditions in seawater with a salt content of 3.5 wt.% + / - 1 wt.% and measuring the peel strength in a peel test before insertion and at the predetermined time after removal from the seawater, and wherein the swelling behavior is characterized by a swelling heave degree, which is formed by the quotient of the volume of the filling layer material including the water absorbed therein at the predetermined time to an initial volume of the filling layer material before the start of swelling, wherein the swelling heave degree is determined by completely immersing a filling layer material layer in a water bath and loading the filling layer material layer with a pressure of 4.5 N / m, 2is determined. According to the invention, the geosynthetic mat has a swelling-degradation ratio which is calculated from the degree of swelling heave divided by the degree of residual peel strength, within the first week after the simultaneous start of the swelling process and the biological degradation process in a range between 1 and 5 and within each predetermined point in time from the beginning of the second to the end of the third month after the start of swelling and degradation in a range between 1.5 and 25, preferably in a range with a lower limit of 2 and / or an upper limit of 15.

[0015] The invention is based on the following findings: Basically, the invention pursues the approach of at least partially, preferably completely, replacing the synthetic components of the geosynthetic mat, which were unavoidably used in particular in previous geosynthetic mats to provide the upper and lower cover layers and the connecting structure, with biodegradable materials, in that the upper and lower cover layers and the connecting structure comprise a biodegradable material or consist of such a biodegradable material.A biodegradable material in the sense of the invention is to be understood as a material that decomposes in a biological, chemical or biochemical process under the typical ambient conditions in a soil installation position, i.e. in a moist environment of a soil layer that can consist of the main components earth, sand, clay and mixtures of these typical soil layer components, in a short or medium term period, which is understood to be a period of a few weeks to a few months, up to two years or several years, e.g. up to 10 years, and thereby transforms into components that are harmless to the environment.

[0016] The reduction in peel strength as a result of this biological degradation process, which is relevant according to the invention, is determined in a composting test. This can be characterized, for example, by a soil composting test with the following ambient conditions: temperature 50°C + / - 5°C; thermophilic conditions according to ISO 16929, or by a marine incubation test with the following ambient conditions: temperature 30°C + / - 2°C; aerobic conditions in seawater with a salt content of 3.5% + / - 1% by weight. It should be understood that the material used according to the invention is, in particular, biodegradable according to the aforementioned soil composting test if it is intended for soil layer sealing beyond a flowing or standing body of water, and is biodegradable according to the aforementioned marine incubation test if it is intended for soil layer sealing in a body of water oron a body of water. The peel strength of a biodegradable material is determined over the biodegradation period by storing the geosynthetic mat under the aforementioned environmental conditions for several different specific periods of time in one of the two suitable tests. After this period, the mat is subjected to a peel test, for example, a drum peel test according to DIN 53295 or a peel test according to DIN EN 28510-1:2014 DE or according to ASTM D6496, in order to determine the progression of the peel strength over time.

[0017] In particular, a composting environment in accordance with Section 5.1 of DIN EN ISO 16929:2018-04 can be provided, i.e. an environment with the following conditions for conducting the composting test: the geosynthetic mat is placed in fresh biowaste with a naturally occurring, ubiquitous microbial population so that this biowaste covers the geosynthetic mat on both sides with a thickness of at least 30 cm, temperature, pH, moisture content, and gas composition are monitored, the composting test is carried out in a container large enough to allow natural self-heating to occur, an air supply system ensures sufficient and uniform gassing, the container can be placed in a climate chamber with a constant chamber temperature, if the compost reaches temperatures above 65°C during the spontaneous thermophilic phase, the diversity of microorganisms can be reduced.

[0018] To restore the full range of thermophilic bacteria, the compost can be re-inoculated with mature compost (about 1% of the total initial mass of the biowaste) of younger origin (maximum 3 months old).

[0019] For the composting test, homogeneous biowaste of the same age and origin is used, which is reduced by shredding or sieving to a particle size of no more than 50 mm. Depending on the type of waste, 10%-60% of a filler made of structurally stable components such as wood chips or bark with a particle size of 10 mm to 50 mm is added. The biowaste must meet the following criteria: the C / N ratio of the mixture of fresh biowaste and filler is between 20 and 30, which can be adjusted with urea if necessary, the moisture content is more than 50% by mass, but there is no free water, the loss on ignition of the dry residue is greater than 50% by mass, and the pH is above 5. In addition to the peel strength, the invention also considers the swelling behavior as a property of the geosynthetic mat, and these properties are adjusted in relation to the peel strength.According to the inventors' findings, the pure degree of swelling cannot be used as a characteristic parameter for the desired long-term impermeability properties of the geosynthetic mat for many applications, because the degree of swelling does not adequately reflect the desired compaction properties of the middle fill layer. Instead, the middle fill layer is designed or characterized with a degree of swelling heave, which describes the increase in volume under a constant pressure, which is realized in the test as the contact pressure on the material layer, for example, by a plate or disc with a corresponding weight.

[0020] It is important to understand that the degree of swelling is taken into account for at least the first month and the following two months. In principle, the degree of swelling can also be considered over a longer period, which results in a good balance of properties, especially for slow-swelling middle fill layers. For some materials, it must be taken into account that they already undergo initial swelling upon exposure to air, for example, because these materials emerge from the production process very dry and water-absorbent.In such cases, it should be understood that the materials are only used in the swelling-heavy test according to the invention in a state that is subsequently established, in accordance with the realistic conditions of intermediate storage in air and the swelling that occurs during this period, in order to avoid falsification of the results by non-representative initial effects that could otherwise occur in the first hours or days of the swelling-heavy test.

[0021] A key factor in the fulfillment of the geosynthetic mat's functions is, firstly, that the upper and lower cover layers and the connecting structure always maintain sufficient counterpressure against the swelling of the middle fill layer. This counterpressure, when timed to match, leads to sufficient compaction of the middle fill layer, particularly in the first few months, and thus to the closure of the pores in the middle fill layer. This achieves the necessary impermeability and can then be maintained over a long period of time, particularly after the swelling has asymptotically approached a maximum degree of swelling and biological degradation has progressed to the point where the peel strength is significantly reduced or close to zero.Secondly, in many applications, it is important that the geosynthetic mat maintains the mechanical properties necessary to prevent slippage at any time after installation on a slope. According to the inventors, an initial slight reduction in peel strength relative to the swelling is crucial to maintain shear strength through the biodegradable structures in an early phase when the stabilizing function of the middle fill layer has not yet developed.

[0022] The period within which the desired properties, characterized by the swelling-degradation ratio, must be present can range from a few weeks to one or two years from the start of swelling and biological degradation.

[0023] Although the use of such biodegradable materials can fundamentally reduce or completely avoid the problem of contaminant transfer or contamination after removal of such a geosynthetic mat, the use of such biodegradable materials is hindered by the fact that the sealing effect of the geosynthetic mat is fundamentally not achieved through biological degradation. This is because the necessary counterpressure is not generated or is not sufficiently generated when the middle fill layer expands. As a result, the geosynthetic mat is too permeable after swelling, which does not achieve the desired sealing function. On the other hand, the biological degradation of the cover layers and the connecting structure reduces the shear strength of the geosynthetic mat to such an extent that slope layers slide when the geosynthetic mat is installed at an angle on a slope.The use of biodegradable geotextiles is therefore seen as critical or unsuitable in many applications with regard to the time requirements for mechanical bonding, and DIN EN 12225 specifies test criteria for geosynthetics to demonstrate general resistance to microbial degradation.

[0024] The geosynthetic mat according to the invention overcomes these problems through a temporally coordinated swelling behavior with the behavior of biodegradation. For this purpose, the composite of the upper and lower cover layers and the connecting structure is characterized according to a residual peel strength level that this composite exhibits due to a biodegradation rate after a certain biodegradation period, i.e., at a predetermined point in time after the start of the biodegradation process and over a subsequent period. This residual peel strength level therefore characterizes the composite of the two cover layers and the connecting structure in terms of how rapidly its peel strength decreases over time due to the biodegradation process, thus representing a curve that reflects the peel strength of the biodegradable material over the time of biodegradation.The slope of the curve at any point in time can be defined as the degree of peel strength reduction. The further the biodegradation progresses, the lower the degree of peel strength reduction. The faster the biodegradation occurs, the steeper the curve of the peel strength reduction falls over time and, consequently, the faster the peel strength of the bond decreases. The reduction in the degree of peel strength reduction can occur through biodegradation of the top cover layer, the bottom cover layer, and / or the bonding structure, or through a reduction in the bonding structure's fastening strength in the top or bottom cover layer.

[0025] On the other hand, the fill layer material of the middle fill layer exhibits a swelling capacity, which is characterized by its water absorption and swelling capacity. This swelling capacity is characterized by the degree of swelling, which is the volume increase of the fill layer material at a specific time after the onset of swelling in relation to the dry volume of the fill layer material before the onset of swelling under a compressive load of 4.5 N / m 2describes and produces a curve over time which represents the increase in the volume of the fill layer material over the swelling period. The higher the degree of swelling, the greater the ability of the fill layer material to swell under load. It should be understood that the degree of swelling of the material is determined without any restriction on the swelling movement, i.e. the material can increase its water content or volume unhindered when determining the degree of swelling. In practice, this can be achieved using a force-controlled test or by placing a vertically freely movable plate with a weight of 4.5 kg per square meter on the fill layer material when determining the degree of swelling.

[0026] The swellable material of the middle filling layer and the biodegradable material of the upper and lower cover layer and, if applicable, also of the connecting structure are now such that the ratio between the degree of swelling of the swellable material to the residual peel strength of the composite of upper and lower cover layer and connecting structure over an initial period of one week is in a range between 1 and 5 and from the beginning of the second to the end of the third month is between 1.5 and 25, preferably between 2 and 15.Through these two temporally successive and coordinated material properties of the middle fill layer on the one hand and the mechanical composite enclosing this middle fill layer on the other hand, it is achieved that in the initial phase of the swelling of the middle fill layer, the upper and lower cover layers and the connecting structure between these two cover layers can build up a sufficiently high mechanical counterpressure against the swelling pressure and can maintain it over such a long period of time that a sufficient compaction of the middle fill layer is effected during this swelling process.In addition, it is ensured that the upper and lower cover layers and, if applicable, the connecting structure have biologically degraded at a later point in time when this swelling has largely or completely ended, and thus pollutant contamination can no longer occur when the geosynthetic mat is removed or when parts of the geosynthetic mat are moved due to erosion.

[0027] According to the inventors' findings, with sufficient homogenization and a reduction in air void volume, the middle fill layer can develop a total shear strength that is at least in the range of, or even exceeds, the shear strength of the geosynthetic mat immediately after installation, i.e., with the middle fill layer not swollen and the initial peel strength of the composite consisting of the upper and lower cover layers and the connecting structure. This reliably prevents the risk of slope sliding due to an unstable layer plane in the form of the geosynthetic mat.

[0028] Through this composition and the relationship of the material properties with regard to the swelling behavior of the middle fill layer and the degradation of the mechanical properties of the upper and lower cover layers, the geosynthetic mat according to the invention achieves sufficiently high impermeability due to the achievable compaction, while simultaneously avoiding the risk of slope slippage. It thus provides the desired hydraulic and mechanical properties in the medium and long term without the associated pollution. The geosynthetic mat according to the invention can therefore be installed without the risk of local environmental pollution and environmental hazards resulting from erosion and relocation, provided the middle fill layer comprises or is made of appropriately environmentally friendly materials. It can also be removed and disposed of cost-effectively during temporary use.

[0029] By maintaining the inventive ranges of the ratio between the degree of swelling and the degree of residual peel strength, which are maintained within the first three months, a balanced development of the impermeability of the geosynthetic mat through swelling and the provision of mechanical strength for the soil layer is achieved, even when installed on a slope and subject to corresponding shear forces.

[0030] It is particularly preferred if the swelling-degradation ratio within the first week after the simultaneous start of the swelling process and the biological degradation process from the third day onwards is in a range between 1.2 and 5. A particularly preferred swelling-degradation ratio in the first week for the installation of the geosynthetic mat with an overlying weighting soil layer is 1.25 to 4, preferably 1.25 to 3. A particularly preferred swelling-degradation ratio in the first week for the installation of the geosynthetic mat without an overlying soil layer is 1 to 4, preferably 1.2 to 3. In principle, the invention can preferably be implemented for different installation situations such that the swelling-degradation ratio in the first week from the third day onwards is in a range which has a lower limit of 1, or 1.25 or 1.5 or 2 and which has an upper limit of 1.75 or 2 or 4 or 6.

[0031] From the beginning of the second to the end of the third month after the start of swelling and degradation, the swelling-degradation ratio is preferably in a range between 1.75 and 20, preferably in a range with a lower limit of 1.75 or 2 or 2.5 or 3 and / or an upper limit of 25 or 20 or 15 or 10.

[0032] It is preferred if the swelling-degradation ratio from the third month until the end of the twelfth month after the start of the swelling process and the biological degradation process is in a range between 2 and 50, preferably in a range with a lower limit of 3 and / or an upper limit of 30. With such a longer period of time, a long-term swelling and degradation process of the geosynthetic mat is recorded and the properties of the geosynthetic mat are such that optimal swelling and degradation behavior is achieved over this longer period.

[0033] According to the inventors' findings, various effects can be advantageously achieved through such a coordinated reduction of peel strength on the one hand and swelling on the other. For example, a significant increase in weight and volume regularly occurs at the beginning of the swelling process, and at this point, a high counterpressure against the swelling pressure is required to achieve the densest possible structure in the middle fill layer. The swelling of the middle fill layer also causes compaction and mechanical stabilization there, which results partly from the swelling under counterpressure itself, which, in many materials that can be used for swellable middle fill layers, but also from a chemical process, results in a stabilized middle fill layer.For example, a phyllosilicate contained in the middle fill layer can transform into another phyllosilicate during the swelling process. For example, sodium bentonite can transform into calcium bentonite, thereby providing greater strength and stability against shear forces from the middle fill layer itself. This transformation process in the middle fill layer therefore allows the peel strength of the stabilizing top layer and connecting structure to decrease with increasing swelling, up to the point of complete degradation of the top layer and connecting structure at a later point.

[0034] A typical example of this is middle fill layers that contain a mineral mixture known as bentonite, with montmorillonite as its main component, in powder or granulate form, or consist of this mineral mixture. This mineral mixture can transform from its initial state, containing sodium bentonite components, into a swollen state containing converted calcium bentonite components, and in the process increases in shear strength. According to the inventors' knowledge, the calcium ions required for this ion exchange are often already present in the bentonite in sufficient quantities, and are always present in additional quantities in the surrounding soil, which can accelerate the process. Over time, the ion exchange from sodium (monovalent) to calcium (divalent) then takes place. The ambient conditions determine how quickly this process proceeds.

[0035] It is particularly preferred if the swelling lift degree one week after the start of the swelling process is greater than 1.25, preferably greater than 1.5 or 2 and / or the swelling lift degree one month after the start of the swelling process is greater than 1.5, preferably greater than 2 or 3, and / or the residual peel strength degree three months after the start of the swelling process is less than 0.95, preferably less than 0.9 or 0.8 and / or the residual peel strength degree twelve months after the start of the swelling process is less than 0.9, preferably less than 0.75 or 0.5. Basically, swelling behavior is to be understood in such a way that the middle filler layer swells to a relevant extent over time and biological degradation behavior is to be understood in such a way that the peel strength decreases to a relevant extent over time.According to this training, not only is the ratio of swelling to biodegradation set within a specific range, but the swelling behavior and the reduction in mechanical strength due to biodegradation are also each isolated within a favorable value range that achieves favorable swelling and a suitable time-scale for biodegradation. Thus, for many applications, rapid swelling is initially important to create a seal, whereas biodegradation can and should preferably take place over a longer period of time.

[0036] It is particularly preferred if the connecting structure comprises needling between the upper and lower cover layers or is formed by such needling. During needling, several individual fibers from this cover layer are pulled through the middle filler layer and hooked into the opposite cover layer by piercing the cover layer with a barbed needle serving as a tool. Such needling can preferably be carried out if the pierced cover layer and / or the opposite cover layer is designed as a nonwoven layer, i.e. as a layer with a disordered fiber structure from which fibers can be pulled out during the needling process and anchored in the opposite layer to thereby form the connecting structure.However, needling is also possible if the anchoring cover layer is formed with ordered fiber structures, for example, knitted, crocheted, or woven cover layers. In this case, the needling preferably always starts with a nonwoven layer as the uppermost cover layer, since in a nonwoven layer the fibers have good mobility perpendicular to the layer plane. In particular, needling can provide a connecting structure that connects the upper and lower cover layers at a plurality of spaced-apart points distributed over the surface of the geosynthetic mat, thereby achieving a connection between the two cover layers that acts over virtually the entire surface of the upper and lower cover layers and is therefore particularly effective against swelling pressure and shear forces.If the connecting structure, particularly the cover layer pierced to create the needle punch, comprises fibers made of a thermoplastic (e.g., PLA, PBS, PBAT), the fibers can be further anchored to the back of the second cover layer by melting them, thus increasing the initial internal shear bond of the geosynthetic mat. This can be achieved, for example, using a flame bar, which melts the fiber portions protruding outward from the second cover layer, causing them to form small nodules that prevent or impede the fibers from being pulled out of the second cover layer toward the first cover layer.

[0037] It is even more preferred if the upper and / or lower cover layer and / or the connecting structure comprises fibers made of the biodegradable material or is formed by such biodegradable fibers. By using fibers made of a biodegradable material, good strength and the possibility of needling can be achieved, while at the same time, such fibers can be biodegraded particularly well in a targeted manner, thus providing the desired ratio of swelling and residual peel strength.

[0038] It is even further preferred if the biodegradable material of the upper cover layer and the lower cover layer are different from one another, or if the biodegradable material of the upper cover layer and the lower cover layer is the same. According to this embodiment, in a first configuration the biodegradable material of the upper and lower cover layers is different, which can be advantageous in certain installation situations and soil structures in order to adapt the geosynthetic mat to local requirements on the top and bottom sides. In contrast, in many applications the second alternative is advantageous, in which the biodegradable material of the upper and lower cover layers are the same, i.e. the two cover layers are made of the same material.This design enables a harmonious, uniform degradation behavior of the upper and lower cover layers, a favorable selection of connection structures between the similar materials and is therefore well suited for many applications.

[0039] According to a further preferred embodiment, it is provided that the biodegradable material of the connecting structure is different from the biodegradable material of the upper cover layer and / or the lower cover layer, or the biodegradable material of the connecting structure is the same as the upper cover layer or the lower cover layer. In these two preferred embodiments, too, in certain installation situations, for example when a particularly high shear strength or a shear strength effective over a long period of time is required, the biodegradable material of the connecting structure can be different from that of the upper and / or lower cover layer, in order to achieve, for example, a slower biodegradation behavior of the connecting structure compared to the cover layers or one of the cover layers.On the other hand, in many common installation situations it is advantageous if the biodegradable material of the connecting structure matches the upper or lower cover layer or both cover layers, thus achieving manufacturing advantages due to the similarity of the materials.

[0040] It is further preferred if the upper and / or lower cover layer comprises a nonwoven layer made of the biodegradable material or is formed by such a nonwoven layer. If the cover layer is designed as such a nonwoven layer or comprises such a nonwoven layer, this allows, on the one hand, a well-adhering support and shear force transfer from surrounding soil layers into the geosynthetic mat, since a nonwoven layer achieves sufficient shear force transfer to adjacent soil layers due to its surface structure. A nonwoven layer is also well suited to needling, as explained above, and can thus facilitate the formation of an efficient connection structure. A nonwoven layer is understood to be a fiber layer in which the fibers are randomly arranged and which has medium-length to continuous fibers in the range of approximately 6 cm to several meters or more.The nonwoven layer can preferably consist of fibers having at least two, preferably more, different fiber thicknesses. A different fiber thickness is understood to mean a difference of at least 100%, i.e., a difference in which fibers with a first diameter and fibers with a second diameter that is twice as large as the first diameter are included in the nonwoven layer. Such nonwoven layers with inhomogeneous fiber thicknesses often allow the biodegradation behavior to be well adapted to the swelling behavior of the middle filler layer.

[0041] It is even more preferred if the upper and / or lower cover layer comprises an ordered textile layer, in particular a knitted, woven, or crocheted textile layer made of the biodegradable material, or is formed by such a textile layer. According to this embodiment, an upper or lower cover layer with an ordered fiber structure is provided, whereby, particularly compared to nonwoven layers, greater strength of the cover layer is achieved in the longitudinal and transverse directions. Furthermore, lower liquid permeability can often be achieved if a close-meshed arrangement of the fibers is implemented in the textile layer.

[0042] It is even more preferred if the middle fill layer comprises a mixture of the swellable material, such as a bentonite powder, in particular sodium bentonite, and a non-swellable aggregate, such as an inorganic bulk material, for example a granulate, in particular sand, glass granulate, chalk, or coal granulate, or is formed by such a mixture. According to this embodiment, a mixture of swellable material and non-swellable tensile aggregate is arranged in the middle fill layer. Both materials are in the form of a bulk material and are preferably homogeneously mixed with one another.By adding such an aggregate, the inventors have found that the shear strength of the middle fill layer can be significantly increased, thereby advantageously influencing the mechanical properties of the geosynthetic mat after extensive or complete biological degradation of the two cover layers and the connecting structure, allowing installation and retention even on steeper slopes. The mixture can be formulated to contain at least 20% by weight of swellable material and at least 20% by weight of aggregate, or at least 30% by weight, 40% by weight of swellable material and at least 30% by weight, or 40% by weight of aggregate.

[0043] It is even more preferred if the middle filler layer comprises a hardening liquid or a hardening liquid, in particular a hard oil such as linseed oil or tung oil, wherein the liquid is preferably only present in a partial region, such as a partial cross-section of the middle filler layer. By adding such a hardening liquid or a hardening liquid, the mechanical load-bearing capacity, in particular with respect to shear stresses on the middle filler layer or with respect to erosion effects acting on the surface, can be further increased, thereby compensating for the biological degradation of the cover layers and the connecting structure. A hardening liquid is understood to be a liquid that changes from a liquid to a solid state, for example through polymer crosslinking or through evaporation of solvent components.A curing liquid, on the other hand, is understood to be a liquid that reacts with other components of the middle fill layer, thereby promoting the curing of the middle fill layer. The liquid can be distributed over the entire middle fill layer and the entire cross-section of the middle fill layer, but it can also be applied only in partial areas, for example, at specific points, in grid strips, longitudinal strips, or transverse strips of the geosynthetic mat. Likewise, the liquid can only be present over a partial cross-section of the middle fill layer, for example, only in a surface area of ​​the middle fill layer or in a central area of ​​the cross-section of the middle fill layer.

[0044] It is further preferred if the geosynthetic mat is further developed by an upper barrier layer arranged adjacent to the upper cover layer and / or a lower barrier layer arranged adjacent to the lower cover layer, wherein each barrier layer is formed by a film, in particular by a film made of a biodegradable material, wherein preferably the upper barrier layer is arranged between the upper cover layer and the middle fill layer, the lower barrier layer is arranged between the lower cover layer and the middle fill layer, the upper cover layer is arranged between the upper barrier layer and the middle fill layer, or the lower cover layer is arranged between the lower barrier layer and the middle fill layer. Such a barrier layer can prevent substances that accelerate or inhibit swelling from soil layers adjacent to the geosynthetic mat from penetrating the middle fill layer and thereby adversely and unpredictably influencing the swelling behavior of the middle fill layer.Such a barrier layer enables a planned, slow swelling behavior from rising soil moisture or targeted irrigation, which is consistent with the biological degradation behavior of the connecting structure and the cover layers. Such a barrier layer can be provided by a polyethylene film, but films made of biodegradable plastics can also be used for the barrier layer. In particular, biodegradable materials that match the upper or lower cover layer can be used for the barrier layer. The barrier layer can be applied during the manufacturing process of the geosynthetic mat in the form of a coating (inline extrusion) or as a finished film by lamination, gluing, or similar.

[0045] According to a further preferred embodiment, the biodegradable material of the upper cover layer, the lower cover layer, and / or the connecting structure comprises fibers or consists of fibers that have a fiber core strand made of a first biodegradable material and a fiber core strand sheath made of a second biodegradable material surrounding the fiber core strand, wherein the first biodegradable material has a first biodegradation rate that is higher than a second biodegradation rate of the second biodegradable material. According to this embodiment, the upper and lower cover layers and / or the connecting structure contain fibers that are composed of a fiber core strand and a fiber core strand sheath, wherein the fiber core strand and fiber core strand sheath are composed of two materials that exhibit different biodegradation behavior rates.According to the inventors' findings, this fiber design achieves a significant advantage in that the degradation behavior of the fiber and thus its reduction in tensile strength occurs discontinuously, i.e., with two successive, distinct degradation phases. In a first phase, the fiber core strand sheath is biologically degraded, whereas the fiber core strand is subject to little or no biological degradation because it is still protected by the fiber core strand sheath from the influences that would cause such biological degradation, such as the effects of radiation or liquid.The fiber core strand therefore retains its mechanical properties completely or almost completely during this first phase. If the fiber's mechanical properties are predominantly characterized by the fiber core strand's mechanical properties, the fiber will suffer little or no loss of mechanical properties during this first phase of biodegradation of the fiber core strand sheath. Only after the fiber core strand sheath has degraded will the fiber core strand be biodegraded, significantly reducing the fiber's mechanical properties. Thus, a fiber constructed in this way initially exhibits a very delayed reduction in its mechanical properties, which then accelerates over time.This is advantageous for the geosynthetic mat according to the invention in many applications, since it allows sufficient mechanical strength to be provided by the cover layers and the connecting structure over a certain period of time, which may, for example, correspond to the typical swelling behavior or the typical remodeling behavior of a middle filling layer, but after this period of time, a rapid biological and complete degradation of the cover layers and the connecting structure with a corresponding reduction in mechanical strength is achieved.

[0046] It is further preferred if the first biodegradable material comprises a natural fiber such as coconut fiber, jute fiber, hemp fiber, bamboo fiber, or flax fiber, or a biodegradable synthetic fiber made of PBS, PBAT, PLA, or a polymer blend of at least two of these materials, or if the biodegradable material comprises a mixture of fiber cores made of natural fibers and synthetic fibers, wherein the weight fraction of the synthetic fibers is preferably greater than 30%, in particular greater than 50%. The use of these fiber materials or mixtures of these fiber materials has proven particularly suitable for many applications in order to achieve the mechanical strengths and biodegradation rates required for a geosynthetic mat with a swellable material in the middle fill layer.

[0047] It is even more preferred if the second biodegradable material comprises a cellulose-based plastic, a starch blend, lyocell, succinic acid (PBS), or a biodegradable polyester such as polybutyrate adipate terephthalate (PBAT), or polylactic acid (PLA). These materials have proven particularly suitable as coating materials because they exhibit sufficiently slow biodegradation behavior while, at the same time, being easy to apply as a coating in liquid form. It should be understood that the fibers in the cover layer or the connecting structure can be designed in such a way that they are already coated before the fiber material is processed into the cover layer, i.e., the cover layers can be made from coated fibers.Alternatively, it may also be provided to produce the cover layers from uncoated fibers, i.e., only from the fiber core strands, and then to coat the entire cover layer with the second biodegradable material in order to also enclose cut fiber ends and to achieve a strengthening of the cover layer through bonding effects at fiber intersections by the second biodegradable material. It is even more preferred if the middle filler layer has a permeability of between 1x10 -5 up to 1x10 -9m / s. According to this embodiment, the geosynthetic mat is provided with a middle fill layer which has a permeability that, in the production state before installation, is initially insufficient to achieve reliable sealing of soil layers. According to the inventors' findings, such permeability can initially be tolerated in many applications or is even desired in order to achieve permeability through the geosynthetic mat in an initial time phase after installation. During this permeability, particles contained in the water that permeates through the geosynthetic mat are deposited in the middle fill layer and, like a clogging filter, lead to compaction and sealing of the middle fill layer. Thus, a colmation process takes place which corresponds to the formation of a filter cake in or on the middle fill layer.This allows for a favorable sealing effect at a particularly high sealing level with a particularly low permeability of the geosynthetic mat. In the initial phase, the geosynthetic mat acts only as a seepage barrier and only achieves its final impermeability after a certain seepage phase, which it then maintains. According to the inventors' findings, this structure of the geosynthetic mat is particularly well suited for sealing in the beds of fluid-bearing streams, such as streams and rivers, and takes advantage of the fact that the fluid in the stream or river carries corresponding particles that can act as a seal.According to one aspect of the invention, this also includes a geosynthetic membrane in which the middle fill layer consists of a material with only very low swelling capacity or a non-swelling material—i.e., a material with a swelling coefficient of 1 over the entire installation period. For example, a middle fill layer composed of sand or other pourable mineral materials can be used for such a sealing effect through colmation.

[0048] A further aspect of the invention is a geosynthetic sheet comprising at least one layer layer comprising fibers or formed by fibers, wherein the fibers have a fiber core strand made of a first biodegradable material and a fiber core strand sheath made of a second biodegradable material surrounding the fiber core strand, wherein the first biodegradable material has a first biodegradation rate and the second biodegradable material has a second biodegradation rate that is different, in particular higher, than the first biodegradation rate of the first biodegradable material. For the purposes of the invention, a geosynthetic sheet, like a geosynthetic mat, is understood to mean a structure that has dimensions in a longitudinal direction and a transverse direction that are many times greater than its thickness.A geosynthetic mat and a geosynthetic sheet can, in particular in the longitudinal direction, have dimensions that are many times greater than their transverse dimensions, i.e., they can be significantly longer than they are wide. Geosynthetic mats and geosynthetic sheets are therefore typically transported in a rolled-up or folded state and then unrolled or unfolded at an installation site so that they can be laid lengthwise. For the purposes of the invention, a geosynthetic mat is to be distinguished from a geosynthetic sheet in that the geosynthetic mat has several layers, whereas a geosynthetic sheet can also have only a single layer, but can also be multi-layered if necessary.

[0049] The geosynthetic membrane according to the invention is characterized in that it is formed from fibers that have an at least two-layer structure, or comprises such fibers. The fibers comprise a fiber core strand and a fiber core strand sheath surrounding this fiber core strand. The fiber core strand and fiber core strand sheath consist of two different biodegradable materials that have different biodegradation rates, i.e., they are biodegraded in such a way that, under the same biodegradation conditions, the first material is biodegraded either faster or slower than the second material. It is preferred that the second material has a biodegradation rate that is lower than the biodegradation rate of the first material, i.e., the second material biodegrades more slowly than the first material.

[0050] As previously in connection with the geosynthetic mat, which may also comprise fibers or a layer of fibers formed in such a way in at least two layers, such a fiber design can achieve a more favorable progression of the mechanical strength during the biological degradation of the fibers or of the layer made from the fibers, in particular in such a way that the fibers retain a high mechanical strength over a longer period of time in a first phase, namely while only the fiber core strand sheath is biologically degraded, whereas then, after the degradation of the fiber core strand sheath has taken place, the mechanical strength of the fibers decreases rapidly in a second phase when the fiber core strand is then degraded.It should be understood that these properties and the further developments therein, which were previously explained with reference to the geosynthetic mat, are also applicable to the geosynthetic sheet, and reference is made thereto accordingly. According to a preferred embodiment, the fibers in the layered layer are present as a random structure, in particular as a nonwoven layer, or as an ordered structure, in particular as a knitted, woven, or crocheted textile layer. Accordingly, the specific fibers of this geosynthetic sheet can be present as a random structure, for example as a nonwoven layer, resulting in the previously explained properties and advantages that also arise in connection with the previously explained geosynthetic mat.Alternatively, the fibers can also be processed as an ordered structure, i.e., knitted, woven, or otherwise arranged in a directional manner. An ordered structure, as previously defined for geosynthetic mats, is understood to be a structure with a regularly repeating geometric pattern of fiber orientation, typically along a straight line or two straight, intersecting lines. With regard to the ordered structure, reference is also made to the properties and advantages previously explained for geosynthetic mats.

[0051] The geosynthetic membrane can then be further developed by covering the fibers circumferentially and end-on with the fiber core strand sheath, in particular by producing the layer in a process in which, in a first step, a fiber core layer is produced from fiber core strands and, in a subsequent second step, the fiber core strands of the fiber core layer are coated with a sheathing material.Such a design with a circumferential and end-side covering of the fiber core strand with the fiber core strand covering can be achieved in particular by first producing the layer from the fiber core strands, for example by processing it into a nonwoven or by weaving, knitting or crocheting it, and then coating the layer thus pre-produced from the fiber core strands with the fiber core strand covering, for example by immersing it in a liquid or wetting it with a liquid in a spraying or coating process, thereby achieving all-round covering of the fibers.This is advantageous in order to achieve the biodegradation properties in the desired manner and is therefore preferred over processes in which the fibers are completely pre-produced and then processed, because in this processing method the frontal fiber core strand cross-sectional ends are exposed by the necessary separation of the fibers and would therefore be accessible to rapid biodegradation.

[0052] A further aspect of the invention is a geosynthetic mat of the previously described structure and functionality, in which the upper and / or lower cover layer comprises a geosynthetic sheet of the previously described structure and functionality or is formed by such a geosynthetic sheet. As previously explained, the properties of such a geosynthetic sheet with the two-layer fibers contained therein can be used particularly advantageously for the geosynthetic mat according to the invention.

[0053] Yet another aspect is the use of a geosynthetic mat of the above-described construction or a geosynthetic sheet of the above-described construction for producing a sealing layer in the soil or at the bottom of a body of water. As already explained above, the geosynthetic mat and the geosynthetic sheet according to the invention are particularly well suited for producing a sealing layer in the soil and are also well suited for producing such a sealing layer at the bottom of a body of water.The balanced properties of providing mechanical peel strength for an initial phase of swelling of the middle fill layer are particularly effective and can achieve secure sealing, whereas the biological degradation of the cover layers and the connecting structure and, if necessary, an additional barrier layer can significantly reduce or completely prevent the environmental impact during the removal of the geosynthetic mat or geosynthetic sheet or in the event of erosion-related discharge of parts of the geosynthetic mat or sheet.

[0054] The use can be advantageously further developed by rolling out the geosynthetic mat in a first step and then impregnating the geosynthetic mat with a liquid, in particular a hard oil, in a subsequent second step. With this method of use, the geosynthetic mat or geosynthetic sheet is first almost completely prefabricated by producing the layers, arranging them relative to one another, and connecting them together. The thus prefabricated geosynthetic mat or sheet is then rolled up for transport. After transport to the installation site, the geosynthetic mat or sheet is then unrolled for installation and then moistened at the installation site with a liquid that influences its further mechanical and / or biological behavior.By impregnating the geosynthetic mat or sheet at a second point in time, following the point in time of production of the geosynthetic mat or sheet, it is avoided that the properties of the geosynthetic mat or sheet can change during storage or transport due to an already completed impregnation with the liquid, but it is achieved that the desired functional and structural property influences by the liquid only begin at the installation site, following the wetting with the liquid that takes place there.

[0055] It should be understood that this impregnation can also consist of the coating of fiber core strands that were processed in pre-production to form a cover layer, a connecting structure or the like in the geosynthetic mat or sheet and which are then provided with an additional coating on site in order to advantageously influence the biodegradation behavior and the mechanical properties.

[0056] In particular, wetting / impregnation can be performed in such a way that it is selected depending on previously measured environmental conditions at the installation site, for example, by adapting a layer thickness to such environmental conditions or by selecting the liquid used for impregnation from several different available liquids or by mixing them. Environmental conditions that can influence this selection or impregnation intensity include, for example, soil moisture content, soil pH, the concentration of substances in the soil that accelerate or slow down the biological degradation process, the intensity of UV radiation at the installation site, and other influencing factors.In principle, it should be understood that for these types of use with pre-wetting, the point in time at which the swelling-degradation ratio is determined and lies within the aforementioned ranges must be determined from the impregnation of the geosynthetic mat, even if the liquid used for impregnation may not yet trigger biological degradation.

[0057] According to yet another preferred development of the use according to the invention, it can be provided that the geosynthetic mat is impregnated with a liquid at a first time before installation, which causes pre-swelling of the middle fill layer, and at a subsequent second time at an installation site in an installation position and in the installation position, swells due to the supply of liquid, in particular from the surrounding soil. According to this embodiment, it is provided that the geosynthetic mat or sheet is impregnated with a liquid before it is laid, which causes pre-swelling of the middle fill layer. Pre-swelling is to be understood here as limited swelling, during which the material of the middle fill layer does not yet exhaust its maximum swelling capacity, i.e. does not swell to its maximum, but only exhausts part of this swelling capacity.Such impregnation with a liquid for pre-swelling can, for example, already take place during the production of the geosynthetic mat or sheet, but can also alternatively be used in such a way that the geosynthetic mat is produced at a first point in time and impregnated for pre-swelling at a second point in time, for example shortly before delivery or transport of the geosynthetic mat to the installation site, so that changes in the geosynthetic mat during any storage between the time of production and the time of transport are avoided. Pre-swelling can be beneficially promoted and serve to positively influence the initial swelling behavior of the geosynthetic mat immediately after installation in the first few days or weeks, thereby avoiding unfavorable structural changes or changes in mechanical properties.

[0058] The liquid with which the geosynthetic mat is impregnated at the initial point in time can be the same as or similar to the liquid that causes swelling at the installation site, for example, impregnation with water. In other applications, however, the liquid with which it is impregnated at the initial point in time can also be different from the liquid with which the geosynthetic mat is wetted at the installation site, for example, it can have a different composition or contain additives that promote pre-swelling, which, for example, also act to promote pre-swelling but inhibit or prevent biological degradation in order to prevent premature biological degradation of the cover layers and the connecting structure due to the impregnation at the initial point in time.

[0059] In this case, it is preferably provided that the geosynthetic mat is first brought into a transportable state after impregnation, in particular by being rolled up or folded for this purpose and then transported to the installation site. In principle, it is preferable to carry out uniform impregnation at the first point in time before the geosynthetic mat is brought into a transportable state, in order to avoid the geosynthetic mat being impregnated differently depending on the location.

[0060] The use according to the invention can be further developed in the use of the geosynthetic mat for producing a sealing layer on the bottom of a body of water, or in the application of the geosynthetic mat for producing a sealing layer in a soil layer, by the geosynthetic mat being laid on the bottom of the body of water at a first point in time or being installed in the area of ​​the bottom of the body of water or being installed in a soil layer, and wherein the upper cover layer of the geosynthetic mat has an open porosity and, as a further improvement, the outer surface of the upper cover layer has an outwardly facing roughness structure and the geosynthetic mat is laid on the bottom of the body of water in such a way that the outer surface of the upper cover layer faces upwards, and wherein the middle filling layer further has a permeability of between 1x10 -5 up to 1x10 -9m / s and that particles carried in the water body above the water body become trapped in the pore structure, further favorably influenced by a reduced flow velocity and reduced drag tension as a result of the roughness structure, and migrate through the upper cover layer into the middle fill layer, so that particles from the water body deposited in the middle fill layer and the upper cover layer form a sealing layer which, at a second point in time following the biological degradation of the upper cover layer, forms a supplementary sealing effect within the swollen middle fill layer and an additional sealing layer at the location of the degraded upper cover layer.

[0061] According to this advantageous use, the geosynthetic mat is deployed such that the middle fill layer initially has a certain permeability value within a defined range, thereby allowing the passage of liquid. This permeability is combined with open porosity and consequently permeability of the upper cover layer and preferably also of the lower cover layer, further enhanced by an outward-facing roughness structure of the outer surface of the upper cover layer, which can be provided, for example, by the typical roughness of a nonwoven layer or an ordered structure of the cover layer produced by weaving, knitting, or crocheting.This ensures that, in an initial phase after installation, the fluid flows through the middle fill layer, allowing particles in the fluid to settle in the middle fill layer and the upper or lower cover layer, thereby reducing permeability. This flow and the associated settling of particles from the flowing fluid in the geosynthetic mat consequently causes a gradual sealing of the geosynthetic mat during this initial phase after installation, which gradually transitions to a state in which permeability is reduced to such an extent that little or no flow occurs, and the geosynthetic mat is sealed at this point.This sealing effect caused by particles at the installation site during an initial phase is known as colmation and can be used to advantage for the overall properties, particularly through the structure of the geosynthetic mat. By constructing the geosynthetic mat in this way and utilizing colmation, it is not necessary for the middle fill layer to swell so much and to work with such a high counterpressure against the swelling behavior within the geosynthetic mat that this swelling behavior alone provides the desired impermeability. This reduces the requirements for the peel strength of the upper and lower cover layers and the connecting structure and also makes it possible to design the middle fill layer in such a way that it only exhibits limited swelling behavior. For example, the middle fill layer can be enriched with aggregates that increase the shear strength of the middle fill layer.The design and use according to the invention consequently makes it possible to provide a middle filling layer with increased shear strength, to reduce the mechanical requirements on the upper and lower cover layer and the connecting structure, also with regard to their biological degradation behavior and the resulting peel strength, and at the same time to achieve a very low permeability in the permanent use of the geoplastic mat.

[0062] It is particularly preferred if the use takes place in such a way that, before laying the geosynthetic mat on the body of water, the amount of particles entrained in the body of water per body of water volume is determined as the particle density, and the geosynthetic mat is designed such that the swelling-degradation ratio and / or the residual peel strength and / or the thickness of the upper cover layer is designed as a function of this particle density, in particular such that the swelling-degradation ratio is smaller, the residual peel strength is greater and / or the thickness of the upper cover layer is smaller, the higher the particle density. According to this embodiment, properties of the body of water are determined before installation of the geosynthetic mat, in particular the amount of particles entrained in the body of water per body of water volume, i.e. the particle density in the body of water.This can include the number of particles, but can alternatively or additionally also include the size of the particles carried along in the body of water. Depending on this determined characteristic of the body of water in relation to the amount of particles, the geosynthetic mat is then adapted accordingly. This adapted design can consist of adjusting the properties of the upper cover layer and / or the properties of the middle fill layer in order to achieve an ideal colmation effect and to ideally adapt the geosynthetic mat to this. For example, in bodies of water that carry a particularly large number of particles, a middle fill layer with a lower degree of swelling heave can be used in the geosynthetic mat than in bodies of water with a low particle density.Similarly, the properties of the upper cover layer can be adapted. For example, in waters with a high particle density, rapid biological degradation with a correspondingly high degree of peel strength reduction can be used. In this case, a rapid sealing effect can be expected due to the colmation effect. Consequently, counterpressure against the swelling of the middle fill layer is not as important as in waters with low particle concentrations, which require such swelling behavior for the geosynthetic mat to achieve a good sealing effect. Furthermore, the surface of the cover layer can be adapted in terms of its roughness structure so that, depending on the waterbody-specific flow conditions and drag tension on the surface of the mat, the deposition and incorporation of particles into the mat can take place reliably.

[0063] A further aspect of the invention is a method for producing a geosynthetic mat, comprising the steps of: providing a first geosynthetic layer, applying a middle filler layer made of a filler layer material comprising a swellable material to the first geosynthetic layer, wherein the filler layer material has a swelling behavior, laying a second geosynthetic layer on the middle filler layer, connecting the first to the second geosynthetic layer through the middle filler layer by means of a connecting structure, in particular by needling, in which a layer made of a first biodegradable material is provided as the first geosynthetic layer and a layer made of a second biodegradable material is applied as the second geosynthetic layer, wherein the upper and lower cover layers have a connection to one another characterized by a peel strength as a result of the connection,which is characterized at the predetermined time after the start of the biological degradation process by a residual peel strength degree, which is formed by the square of a quotient of a reduced peel strength, which the upper and lower cover layers and the connecting structure have at the predetermined time, to an initial peel strength, which the upper and lower cover layers and the connecting structure have before the start of a biological degradation process, wherein the residual peel strength degree is determined in a composting test by completely inserting the geosynthetic mat in compost and composting in a temperature range above 25°C and below 65°C until the predetermined time and measuring the peel strength in a peel test before insertion and at the predetermined time after removal from the compost, and wherein the swelling behavior is characterized by a swelling degree,which is formed by the quotient of the volume of the filling layer material including the water absorbed therein at the predetermined time to an initial volume of the filling layer material before swelling begins, wherein the swelling lift degree is determined by completely immersing a filling layer material layer in a water bath and loading the filling layer material layer with a pressure of 4.5 N / m, 2 is determined, and in which a swelling-degradation ratio which is formed from the swelling lift divided by the residual peel strength within the first week after the simultaneous start of the swelling process and the biological degradation process is in a range between 1 and 5 and within each predetermined point in time from the beginning of the second to the end of the third month after the start of swelling and degradation is in a range between 1.5 and 25, preferably in a range with a lower limit of 2 and / or an upper limit of 15.

[0064] With regard to the manufacturing process, it should be understood that the properties of the geosynthetic mat with regard to the degree of residual peel strength and the degree of swelling heave and the resulting swelling-degradation ratio over time and in terms of their magnitude can be developed as previously explained with regard to the geosynthetic mat.

[0065] Furthermore, a specific roughness structure of the surface can be created by applying a structural material with a degradation behavior that matches the degradation rate of the first or second cover layer or a third degradation rate, and needling the structural material with the geosynthetic layers. The method according to the invention can be used in particular for producing a geosynthetic mat with the properties described above and allows the provision of a geosynthetic mat that is suitable for the use described above at the installation site.

[0066] It should be understood that the steps performed in the method preferably lead to the previously explained structural and functional properties and advantages of the geosynthetic mat according to the invention and enable the previously explained use. With regard to these method steps, reference is made to the previous explanation of the corresponding properties and advantages.

[0067] In this case, the method explained above and the development of the method according to the invention explained above can preferably be developed such that the first and / or the second biodegradable material is in fiber form, in particular as fibers which have a fiber core strand made of a first biodegradable material and a fiber core strand sheath made of a second biodegradable material, wherein the first biodegradable material has a first biodegradation rate which is higher than a second biodegradation rate of the second biodegradable material.According to this method development, the first and / or second biodegradable material is formed from fibers that have a two-layer structure, i.e., a fiber core strand and a fiber core strand sheath. The fiber core strand sheath can be present before the respective layers or the connecting structure are manufactured from the fibers, can be applied subsequently during the production process, or can be applied on-site at the installation site. In this regard, reference is made to the previous explanation of corresponding fibers used in the geosynthetic mat according to the invention or a corresponding geosynthetic sheet.

[0068] The method can be further developed by producing the first and / or second cover layer from the fiber core strands in a first step, and then coating the fiber core strands in the first and / or second cover layer with the fiber core strand sheathing in a subsequent second step. According to this development, the fiber core strand sheathing is applied only after the cover layer has been produced from the fiber core strands, thereby achieving a comprehensive coating of the fiber core strands, including any cut edges on the front side. Reference is also made to the previous description in this regard.

[0069] It is even more preferred if the upper and / or lower cover layer, the middle fill layer, or the entire geosynthetic mat is impregnated with a liquid, in particular with a hardening liquid such as a hard oil. This production step of impregnation with a liquid such as a hard oil can again be carried out directly during the production of the geosynthetic mat at the production site, but can also be carried out subsequently, for example, immediately before the geosynthetic mat is transported to an installation site or after the geosynthetic mat is transported to the installation site, for example, already with the geosynthetic mat laid out. The previously explained advantages of a delayed impregnation with the liquid also apply in this regard to the method according to the invention.

[0070] It is further preferred if a non-swellable aggregate, particularly sand, is additionally applied when applying the middle fill layer. Applying a non-swellable tensile aggregate can, on the one hand, influence the swelling behavior of the middle fill layer, for example, to promote colmation. On the other hand, the shear strength of the middle fill layer is increased, thereby improving the suitability of the geosynthetic mat for installation in shear-loaded installation situations, such as on slopes. This is particularly advantageous after biological degradation of the upper and lower cover layers and the connecting structure.

[0071] Preferred embodiments of the invention are explained with reference to the attached figures. Figure 1 shows a schematic, perspective, partially sectioned, and partially fanned-out representation of a geoplastic mat according to the invention,

[0072] Figure 2 is a cross-sectional longitudinal view of a second embodiment of a geosynthetic mat according to the invention,

[0073] Figure 3 is a perspective, sectional view of a fiber for producing a geosynthetic mat according to the invention,

[0074] Figure 4 shows a second embodiment of a fiber for producing a geosynthetic mat according to the invention in a longitudinal section side view,

[0075] Figure 5 is a schematic diagram of the course of the peel strength and swelling over time of a geosynthetic mat according to the invention.

[0076] Referring first to Fig. 1, a preferred embodiment of the geosynthetic mat according to the invention is constructed from a total of five layers. The uppermost layer is a first sealing layer 10, which is made of a biodegradable plastic as a liquid-tight film and covers the upper surface of the geosynthetic mat as a fluid barrier.

[0077] Below and adjacent to this upper sealing layer 10 is an upper cover layer in the form of a nonwoven layer 20. This nonwoven layer is constructed of randomly laid fibers and typically has a thickness greater than the sealing layer 10, in particular three to ten times greater than the thickness of the sealing layer 10.

[0078] Arranged beneath and adjacent to the upper cover layer 20 is a middle fill layer in the form of a layered silicate made of sodium bentonite. The thickness of this middle fill layer 30 is greater than the thickness of the nonwoven layer 20, typically by a factor of 5 to 20 greater than the thickness of the nonwoven layer 20. This middle fill layer is composed of a mixture of sodium bentonite particles and sand particles and can be impregnated with linseed oil, for example, depending on the application. Due to this composition, the middle fill layer is able to initially exhibit basic strength and groundwater impermeability and to further increase this strength and water impermeability through the swelling of the sodium bentonite in the composition with surrounding moisture, such as soil moisture. As a result of this swelling process, the sodium bentonite is converted into calcium bentonite, which solidifies the middle fill layer.It should be understood that the middle fill layer can also be composed differently and even then have an initial basic strength and initial basic density that can increase through swelling from surrounding moisture. For example, the middle fill layer can be composed exclusively of a swellable material such as bentonite or phyllosilicate, or aggregates other than sand can be used. Impregnation with linseed oil can be replaced or supplemented by other liquids such as hard oils, or such impregnation can be omitted.

[0079] A second sealing layer 40 is arranged beneath the middle fill layer 30, which is designed to match the first sealing layer 10. The first sealing layer 10 and the second sealing layer 40 prevent swelling-accelerating or swelling-inhibiting agents from the surrounding soil layers from penetrating the middle fill layer immediately after installation of the geosynthetic mat and thereby adversely affecting the swelling behavior.

[0080] Finally, a geotextile layer 50 composed of woven fibers is arranged below and adjacent to the second sealing layer 40. The fibers in the geotextile layer 50 are thus aligned in an orderly manner, here in a rectangular grid pattern, and ensure good longitudinal and transverse load-bearing capacity of the geosynthetic mat.

[0081] The entire geosynthetic mat is secured to each other by needling 11 in the thickness direction, i.e., perpendicular to its longitudinal and transverse extents. The needling fixation comprises a multitude of individual needling holes distributed over the entire surface of the geosynthetic mat and can be arranged, for example, in columns and rows or pseudo-randomly. This needling connects the upper and lower cover layers across the surface, and the composite of the upper and lower cover layers and needling therefore exhibits resistance to peeling of the upper cover layer or the lower cover layer from the composite—i.e., a peel strength.

[0082] The needling can be achieved by inserting a barbed needle vertically through the geosynthetic mat, thereby picking up fibers from the nonwoven layer 20 and / or the geotextile layer 50 and pulling these fibers vertically through the geosynthetic mat. These fibers become entangled in the geotextile layer 50 and the nonwoven layer and can also be additionally entangled in the sealing layers 10 and 40. This entanglement and entanglement can be further reinforced by welding or knotting to strengthen the needling attachment.Instead of such needling, other methods can be used to secure the layers in the geosynthetic mat to one another. For example, the geosynthetic mat can be sewn together, for example, by sewing with a fiber in the same pattern as the needling. This allows the sewing thread to be guided vertically through the geosynthetic mat at multiple points, thereby securing and stabilizing the layers to one another. For applications in channels and waterways involving colmation effects, layer 10 can be replaced by a surface roughness structure, and layer 40 can be omitted to achieve initial flow.

[0083] It should be understood that the geosynthetic mat extends in a longitudinal direction LR and a transverse direction QR and can, in particular, be wound along the longitudinal direction LR. The edges of the geosynthetic mat can be sealed in such a way that the first sealing layer 10 and the nonwoven layer 20, as well as the lower sealing layer 40 and the textile layer 50, project laterally beyond the middle fill layer in the transverse direction, and these projecting areas are sewn together to also enclose the middle fill layer laterally.

[0084] Fig. 2 shows a second embodiment of a geosynthetic mat according to the invention in a cross-sectional longitudinal view. Here, too, a central filler layer 130 is arranged centrally. Above and below, respectively adjacent to this central filler layer, are arranged a first sealing layer 110 and a second sealing layer 140, which consequently, unlike the first embodiment of Fig. 1, are placed directly adjacent to the central filler layer. A nonwoven layer 120 is arranged above the first sealing layer as the upper cover layer, and a textile layer 150 is arranged below the second sealing layer 140 as the lower cover layer.Again, the individual layers of the geoplastic mat are fixed and secured to each other by needling 111; furthermore, it can be seen that in the transverse direction, the upper cover layer, the first sealing layer, the second sealing layer and the lower cover layer protrude laterally and are sewn or needled together along a side edge in order to also close off the middle filling layer laterally.

[0085] Fig. 3 shows a fiber from which the connecting structure, for example as needling 11, the nonwoven layer 20, 120 or the textile layer 50, 150 can be formed or which can be enclosed in such a layer. The fiber comprises a fiber core strand 210 which consists of a first biodegradable material. A fiber core strand sheath 220 which consists of a second biodegradable material is arranged around the fiber core strand as a cylindrical sheath. The first biodegradable material has greater strength and a faster biodegradation rate than the second biodegradable material. If the fiber constructed in this two-layer manner is subjected to a biodegradation process and is also intended to absorb mechanical loads over a limited period of time, this results in a favorable profile of the mechanical resilience of this fiber.During this process, the mechanical strength is initially reduced only slightly or not at all, because only the fiber core strand sheath biodegrades, which makes no significant contribution to the mechanical properties. Only after the degradation of the fiber core strand sheath 220 does the fiber core strand 210 also degrade, which then leads to a rapid reduction in the mechanical strength of this fiber.

[0086] Fig. 4 shows a longitudinally sectioned side view of a short- or medium-length fiber according to the invention. This fiber also comprises a fiber core strand 310, which is covered by a fiber core strand sheath 320. With regard to their mechanical properties and their biodegradation rate, the fiber core strand and fiber core strand sheath 310, 320 are designed in a similar manner to the previously explained embodiment according to Fig. 3. As can be seen from Fig. 4, the fiber core strand sheath 320 surrounds the fiber core strand 310 on all sides, i.e., including 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 an all-round sheath that is favorable for biological and mechanical degradation behavior.

[0087] Fig. 5 shows a schematic diagram of the peel strength S(t) of a composite made up of two needle-punched nonwoven layers, which is constructed from fibers according to Fig. 3 or Fig. 4 and consequently comprises or consists of fibers which have a fiber core strand and a fiber core strand sheath. As can be seen from the course of this curve, the curve initially falls only slightly over an initial period of time, which consequently corresponds to only a slight reduction in tensile strength. Only at a time t, at which the fiber core strand sheath has largely completely biodegraded, does the peel strength of the composite then fall more steeply, because from this time t the fiber core strand biodegrades and thus reduces the peel strength of the fiber, which is significantly influenced by it.In this exemplary embodiment, the peel strength of the composite as a whole is influenced by the biodegradation of the fibers in the upper and lower cover layers and the connecting structure, i.e., the needling. It should be understood that in other composite systems, isolated degradation behavior can also significantly or solely influence the decrease in peel strength, for example, when a non-biodegradable connecting structure connects two cover layers, one or both of which are biodegradable, as can be achieved, for example, by sewing. In this case, the peel strength is influenced only by the anchoring strength of the connecting structure in the biodegradable cover layer.

[0088] Figure 5 further illustrates the swelling behavior of a middle fill layer, represented by the curve Q(t) as the degree of swelling of the middle fill layer. As can be seen, after an initial short delay, the middle fill layer initially increases rapidly in volume, corresponding to a rapid initial swelling, before transitioning to a slower volume increase corresponding to a slower swelling, which then asymptotically approaches a final swelling state.

[0089] From Fig. 5 it can further be seen that a geosynthetic mat which would have a layer layer as upper and lower cover layer, which are made of fibers which would have the peel strength behavior according to S(t) and which are also needled with such fibers, through a middle filler layer with a swelling behavior according to Q(t), would still have a high peel strength during the significant part of the swelling of the middle filler layer and consequently could oppose the swelling pressure with a sufficiently high counterpressure in order to achieve the desired good homogenization and removal of the air pores of the middle filler layer by the swelling.Only after swelling is largely complete and only slight volume and weight increases of the middle fill layer due to residual swelling occur, do the biodegradable fibers of the upper and lower cover layers and the needling enter the phase of rapid biodegradation and, consequently, a rapid reduction in peel strength – i.e., a high degree of peel strength reduction. At this point, no significant counterpressure against swelling is required; instead, the geosynthetic mat benefits from a middle fill layer that has already swollen and sealed.

[0090] The calculation of the source-to-degradation ratio is explained in more detail below using four examples:

[0091] 1.) The volume of the middle fill layer swelling under a load of 45 Pa in the swelling test after one week of swelling is 40 liters, and after three months, 50 liters. The volume before the start of swelling was 20 liters. This results in a doubling of the volume within one week, thus a swelling degree of 2, and a swelling degree of 2.5 after three months. The peel strength at the beginning of the composting test is 120 N / 10 cm, which remains virtually unchanged within the first week, and the peel strength after three months of composting is 90 N / 10 cm. This results in a 25% reduction in peel strength after three months, thus a residual peel strength of 0.56. This results in a swelling-to-degradation ratio of 2 after one week and a swelling-to-degradation ratio of 4.4 after three months.

[0092] 2.) The volume of the middle fill layer, which swells under a load of 45 Pa in the swelling test, is 60 liters after one week of swelling, 80 liters after three months, and then no longer increases significantly. The volume before the start of swelling was 20 liters. This results in a tripling of the volume within one week, thus a swelling heave level of 3 and a swelling heave level of 4 after three or more months. The peel strength at the beginning of the composting test is 120 N / 10 cm, which decreases to 115 N / 10 cm within the first week. The peel strength after three months of composting is 60 N / 10 cm, and drops to 40 N / 10 cm by the twelfth month. This results in an approximately 4% reduction to a residual peel strength of 0.96 within the first week, a 50% reduction in peel strength after three months, i.e. a residual peel strength of 0.25 and a residual peel strength of 0.1 after twelve months.This results in a swelling-to-degradation ratio of 3.1 after one week, which increases to 16 after three months and to 36 after twelve months.

[0093] 3.) The volume of the middle fill layer which swells in the swelling test under a load of 45 Pa after one week of swelling is 30 liters, after three months 40 liters and after twelve months also 40 liters. The volume before swelling began was 20 liters. This results in a swelling heave factor of 1.5 after one week and a swelling heave factor of 2 after three and twelve months. The peel strength at the start of the composting test is 120N / 10cm, which remains virtually unchanged within the first week and the peel strength after three months of composting is 90N / 10cm and falls to 60N / 10cm by the twelfth month. This results in a residual peel strength factor of 0.56 after three months and a residual peel strength of 0.25 after twelve months. This results in a swelling-degradation ratio of 1.5 after one week, which increases to 3.6 after three months and to 8 after twelve months.

[0094] 4.) The volume of the middle fill layer swelling under a load of 45 Pa in the swelling test after one week of swelling is 40 liters, after three months 60 liters, and after twelve months 80 liters. The volume before swelling began was 20 liters. This results in a swelling degree of 2 after one week and a swelling degree of 3 after three months and 4 after twelve months. The peel strength at the beginning of the composting test is 120 N / 10 cm, which reduces to 110 N / 10 cm within the first week. The peel strength after three months of composting is 40 N / 10 cm and drops to 20 N / 10 cm by the twelfth month. This results in a residual peel strength of 0.84 after one week, a residual peel strength of 0.11 after three months, and a residual peel strength of 0.03 after twelve months. This results in a swelling-to-degradation ratio of 2.4 after one week, which increases to 27 after three months and to 133 after twelve months.

[0095] In the present examples, Examples 1, 2 and 3 therefore represent geosynthetic mats that have particularly preferred properties according to the invention and achieve good sealing properties. The geosynthetic mat according to Example 4 exhibits rapid swelling behavior with regard to rapid biological degradation and the associated loss of peel strength; this inventive

[0096] Geosynthetic mats may possibly achieve good sealing properties even under heavy load from an overlying soil layer, but are less suitable if such a weight load is not present to compensate for rapid biological degradation, because then there is too little swelling counterpressure to achieve good sealing.

Claims

Claims: Geosynthetic mat, comprising: an upper cover layer, a lower cover layer, a middle filler layer arranged between the upper cover layer and the lower cover layer, made of a filler layer material comprising a swellable material, wherein the filler layer material has a swelling behavior, a connecting structure by means of which the upper and lower cover layers are mechanically connected to one another at several positions through the middle filler layer, wherein the positions of the connection are spaced from one another, preferably at a regular distance from one another along positions following a straight line, so that the upper and lower cover layers have a peel strength to one another due to the connecting structure, characterized in that the upper cover layer and / or the lower cover layer consist of a biodegradable material or comprise a biodegradable material,wherein the peel strength at a predetermined time after the start of the biodegradation process is characterized by a residual peel strength degree which is formed by the square of a quotient of a reduced peel strength which the upper and lower cover layers and the connecting structure have at the predetermined time to an initial peel strength which the upper and lower cover layers and the connecting structure have before the start of a biodegradation process, wherein the residual peel strength degree o in a composting test by completely immersing the geosynthetic mat in compost and composting in a temperature range above 25°C and below 65°C up to the predetermined time and measuring the peel strength in a peel test before immersion and at the predetermined time after removal from the compost, or o in a marine incubation test,with the following environmental conditions:; temperature 30°C + / - 2°C; aerobic, Conditions in seawater with a salt content of 3.5 wt.% + / - 1 wt.% and measurement of the peel strength in a peel test before insertion and at the predetermined time after removal from the seawater; and wherein the swelling behavior is characterized by a swelling heave degree, which is formed by the quotient of the volume of the filling layer material including the water absorbed therein at the predetermined time to an initial volume of the filling layer material before swelling begins, wherein the swelling heave degree is determined by completely immersing a filling layer material layer in a water bath and loading the filling layer material layer with a pressure of 4.5 N / m 2is determined in which a swelling-degradation ratio, which is formed from the swelling lift divided by the residual peel strength, lies in a range between 1 and 5 within the first week after the simultaneous start of the swelling process and the biological degradation process and from the beginning of the second to the end of the third month after the start of swelling and degradation in a range between 1.5 and 25, preferably in a range with a lower limit of 2 and / or an upper limit of 15.

2. Geoplastic mat according to claim 1, characterized in that the swelling-degradation ratio from the third month until the end of the twelfth month after the start of the swelling process and the biological degradation process is in a range between 2 and 50, preferably in a range with a lower limit of 3 and / or an upper limit of 30.

3. Geosynthetic mat according to one of the preceding claims, characterized in that the swelling heave rate one week after the start of the swelling process is greater than 1.25, and / or the swelling heave rate one month after the start of the swelling process is greater than 1.5, and / or the residual peel strength rate three months after the start of the swelling process is less than 0.95, and / or the residual peel strength twelve months after the start of the swelling process is less than 0.

75. Geosynthetic mat according to one of the preceding claims, characterized in that the connecting structure comprises needling between the upper and lower cover layers or is formed by such needling. Geosynthetic mat according to one of the preceding claims, characterized in that the upper and / or lower cover layers and / or the connecting structure comprises fibers made of the biodegradable material or is formed by such biodegradable fibers. Geosynthetic mat according to one of the preceding claims, characterized in that the biodegradable material of the upper cover layer and the lower cover layer is different from one another, or the biodegradable material of the upper cover layer and the lower cover layer is the same.Geosynthetic mat according to one of the preceding claims, characterized in that the biodegradable material of the connecting structure is different from the biodegradable material of the upper cover layer and / or the lower cover layer, or the biodegradable material of the connecting structure is the same as the upper cover layer or the lower cover layer. Geosynthetic mat according to one of the preceding claims, characterized in that the upper and / or the lower cover layer comprises a nonwoven layer made of the biodegradable material or is formed by such a nonwoven layer. Geosynthetic mat according to one of the preceding claims, characterized in that the upper and / or the lower cover layer is an ordered textile layer, in particular a warp-knitted, woven or crocheted layer. Textile layer made of the biodegradable material or is formed by such a textile layer.

10. Geosynthetic mat according to one of the preceding claims, characterized in that the filling layer material comprises a mixture of the swellable material, such as a bentonite powder, in particular sodium bentonite, and a non-swellable aggregate, such as an inorganic bulk material, in particular sand, glass granules, chalk or coal granules, or is formed by such a mixture. 1 1. Geosynthetic mat according to one of the preceding claims, characterized in that the middle filling layer comprises a hardening or hardening-leading liquid, in particular e.g. a hard oil or wax or varnish based on e.g. linseed oil or tung oil, wherein the liquid can also be present only in a partial area such as a partial cross-section of the middle filling layer.

12. Geosynthetic mat according to one of the preceding claims, characterized by an upper barrier layer arranged adjacent to the upper cover layer and / or a lower barrier layer arranged adjacent to the lower cover layer, wherein each barrier layer is formed by a film, in particular by a film made of a biodegradable material, wherein preferably the upper barrier layer is arranged between the upper cover layer and the middle filler layer, the lower barrier layer is arranged between the lower cover layer and the middle filler layer, the upper cover layer is arranged between the upper barrier layer and the middle filler layer, or the lower cover layer is arranged between the lower barrier layer and the middle filler layer.

13. Geosynthetic mat according to one of the preceding claims, characterized in that the biodegradable material of the respective barrier layer is identical or different to the biodegradable material of the upper or lower cover layer to which the film is adjacent.

14. Geosynthetic mat according to one of the preceding claims, characterized in that the biodegradable material of the upper cover layer, the lower cover layer and / or the connecting structure comprises fibers or consists of fibers which have a fiber core strand made of a first biodegradable material and a fiber core strand sheath made of a second biodegradable material surrounding the fiber core strand, wherein the first biodegradable material has a first biodegradation rate which is higher than a second biodegradation rate of the second biodegradable material.

15. Geosynthetic mat according to the preceding claim, characterized in that the first biodegradable material comprises or consists of a natural fiber such as coconut fiber, jute fiber, hemp fiber, bamboo fiber or flax fiber or a biodegradable synthetic fiber made of PBS, PBAT, PLA or a polymer blend of at least two of these materials, or that the biodegradable material comprises a mixture of fiber cores made of natural fibers and synthetic fibers, wherein the weight proportion of the synthetic fibers is preferably greater than 30%, in particular greater than 50%.

16. Geosynthetic mat according to one of the preceding claims, characterized in that the second biodegradable material comprises or consists of a cellulose-based plastic, a starch blend, lyocell, succinic acid (PBS), a biodegradable polyester such as polybutyrate adipate terephthalate (PBAT) or polylactic acid (PLA) or a wax.

17. Geosynthetic mat according to one of the preceding claims, characterized in that the middle filling layer has a permeability between 1x10 -5 up to 1x10 -9 m / s is marked.

18. Geosynthetic membrane comprising at least one layer layer comprising fibers or formed by fibers, characterized in that the fibers comprise a fiber core strand made of a first biodegradable material and a fiber core strand sheath made of a second biodegradable material surrounding the fiber core strand wherein the first biodegradable material has a first biodegradation rate and the second biodegradable material has a second biodegradation rate which is different, in particular higher, than the first biodegradation rate of the first biodegradable material.

19. Geosynthetic membrane according to claim 17, characterized in that the fibers in the layer Present as a disordered structure, especially as a nonwoven layer, or Present as an ordered structure, particularly as a knitted, woven or crocheted textile layer.

20. Geosynthetic sheet according to claim 18 or 19, characterized in that the fibers are covered circumferentially and at the end faces with the fiber core strand covering, in particular by producing the layer layer in a process in which, in a first step, a fiber core layer layer is produced from fiber core strands and, in a subsequent second step, the fiber core strands of the fiber core layer layer are coated with a covering material.

21. Geosynthetic mat according to one of claims 1-17, characterized in that the upper and / or lower cover layer comprises a geosynthetic sheet according to one of claims 18, 19 or 20 or is formed by such a geosynthetic sheet.

22. Use of a geosynthetic mat according to one of the preceding claims 1-21 for producing a sealing layer in the ground or on the bottom of a body of water.

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

24. Use according to claim 22 or 23, characterized in that the geosynthetic mat is impregnated with a liquid at a first time prior to installation, which causes a partial pre-swelling of the middle fill layer. At a subsequent second time, the mat is installed in an installation position at an installation site and subsequently expands in the installation position due to the supply of liquid, in particular from the surrounding soil. Use according to claim 24, characterized in that the geosynthetic mat is brought into a transportable state after the first time, in particular is rolled up, and transported to the installation site.Use according to one of claims 22 to 25 for producing a sealing layer on the bottom of a body of water, characterized in that the geosynthetic mat is laid on the bottom of a body of water at a first time, that the upper cover layer of the geosynthetic mat has an open porosity and the outer surface of the upper cover layer has an outward-facing roughness structure and the geosynthetic mat is laid on the bottom of the body of water in such a way that the outer surface of the upper cover layer faces upwards, and that the middle filling layer has a permeability of between 1x10. -5 up to 1x10 -9m / s and that particles carried in the water body above the water body become trapped in the roughness structure and migrate through the upper cover layer into the middle fill layer, so that particles from the water body deposited in the middle fill layer and the upper cover layer form a sealing layer which, at a second point in time following the biological degradation of the upper cover layer, forms a supplementary sealing effect within the swollen middle fill layer and an additional sealing layer at the location of the degraded upper cover layer.Use according to claim 26, characterized in that before laying the geosynthetic mat on the water bed, the quantity of particles carried in the water per water volume is determined as the particle mass density and the geosynthetic mat is designed such that the swelling-degradation ratio and / or the residual peel strength and / or the thickness of the upper cover layer is designed as a function of this particle mass density, in particular such that. The higher the particle density, the greater the swelling-to-degradation ratio, the lower the residual peel strength, and / or the smaller the thickness of the upper cover layer. A method for producing a geosynthetic mat, comprising the steps: Providing a first geosynthetic layer, Applying a middle filling layer made of a filling layer material comprising a swellable material to the first geosynthetic layer, wherein the filling layer material has a swelling behavior, Laying a second geosynthetic layer on the middle fill layer, Connecting the first to the second geosynthetic layer through the middle filling layer by means of a connecting structure, in particular by needling, characterized in that a layer made of a first biodegradable material is provided as the first geosynthetic layer and a layer made of a second biodegradable material is applied as the second geosynthetic layer, wherein the upper and lower cover layers have a connection to one another characterized by a peel strength, which at the predetermined time after the start of the biodegradation process is characterized by a residual peel strength degree, which is determined by the square number of a quotient of a reduced peel strength, which the upper and lower cover layers and the connecting structure have at the predetermined time, to an initial peel strength,which has the upper and lower cover layer and the connecting structure before the start of a biological degradation process, wherein the residual peel strength is determined in a composting test by completely placing the geosynthetic mat in compost and composting in a temperature range above 25°C and below 65°C until the predetermined time and measuring the peel strength in a peel test before insertion and at the predetermined time after removal from the compost, wherein the swelling behavior is characterized by a swelling degree which is formed by the quotient of the volume of the filling layer material including the water absorbed therein at the predetermined time to an initial volume of the filling layer material before the start of swelling, wherein, - M - the degree of swelling caused by completely immersing a layer of filling material in a water bath and loading the layer of filling material with a pressure of 4.5 N / m 2is determined, and in which a swelling-degradation ratio which is formed from the swelling lift divided by the residual peel strength within the first week after the simultaneous start of the swelling process and the biological degradation process is in a range between 1 and 5 and within each predetermined point in time from the beginning of the second to the end of the third month after the start of swelling and degradation is in a range between 1.5 and 25, preferably in a range with a lower limit of 2 and / or an upper limit of 15.Method according to claim 28 or the preamble of claim 28, wherein 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, characterized in that the first and / or the second biodegradable material is in fiber form, in particular as fibers which have a fiber core strand made of a first biodegradable material and a fiber core strand sheath made of a second biodegradable material, wherein the first biodegradable material has a first biodegradation rate which is higher than a second biodegradation rate of the second biodegradable material.A method according to claim 29, characterized in that, in a first step, the first and / or second cover layer is produced from the fiber core strands, and in a subsequent second step, the fiber core strands in the first and / or second cover layer are coated with the fiber core strand coating. A method according to any one of claims 29-30, characterized in that the upper and / or lower cover layer, the middle fill layer, or the entire geosynthetic mat is impregnated with a liquid, in particular a water-repellent liquid, preferably oil, preferably with a hardening water-repellent liquid, such as a hard oil or a varnish based thereon. Method according to one of claims 29-31, characterized in that when applying the middle filling layer, a non-swellable aggregate, in particular sand, is additionally applied.

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