Patent Application
20160047109
The invention relates to a cutter and a method for improving and strengthening a dike as well as to an improved and strengthened dike body.
In the state of the art, dikes are known that comprise a dike body extending between a land area and a water area, said dike body comprising a longitudinal barrier screen that is oriented substantially standing, for preventing soil particles to be transported through said dike body.
A strengthened dike body as aimed by the present invention provides the advantage that the area protected by the dike in some instances can be reduced, with the consequence that closer to the dike, or even on the dike, building will become allowed. Hence, the economic value will be improved drastically.
The use of a continuous barrier screen in a dike body is to prevent weakening of the dike by tunnel shaped spaces under the dike. Without such barrier screen soil particles may flow under the dike together with seepage water due to a height difference between water at the outer dike part of the dike and the landbased part of the dike. The tunnel shaped spaces may eventually lead to weakening or breakthrough of the dike. This problem of weakening of a dike body due to tunnel shaped spaces is identified as “piping”.
In the state of the art the piping problem is obviated by means of civil technical solutions. For example, barrier screens may be provided inside the dike body so as to stop seepage water with soil particles. These known barrier screens are made of sheet pilings manufactured from concrete or steel.
A disadvantage of the use of steel sheet pilings in a dike for preventing the piping problem is that said piling must be forced into the ground by using high power equipment and that generates vibrations that may lead to damage in the surroundings and/or in the dike body. Such method also generates lots of noise disturbances in the surroundings.
In case of a concrete piling a first step consists of making a trench in which concrete is to be poured. Such method requires the use of many different apparatuses and devices; also, transport of equipment is cumbersome and complex.
From WO97/17497 it is known to make a barrier screen in a dike body wherein soil material of the dike body, when transporting a cutter in a longitudinal direction of the dike body, is mixed with a binder for mutually binding the dike body's soil material for strengthening said dike body.
As a matter of fact, it has shown that making a watertight seal in a dike body does not provide a sufficient solution. For, when a watertight seal is made in the landbased part of a dike body, the risk of cumulating water is obtained at the landbased part of the dike. Since a sheet piling acts sealingly, this will result in accumulation of water inside said dike body. Such leads to saturation of the dike and swelling of water between the sheet piling and the dike body. So as to prevent occurrence of this an additional relief system may be necessary, comprising drainpipes for draining said seepage water.
The techniques available in the art therefore do not provide an adequate means for providing a seal in a dike body.
According to an aspect of the present invention it is aimed at providing a means as mentioned in the preamble for making a barrier screen in a dike body.
The invention further aims at providing such means for quickly and accurately making a barrier screen.
According to a further aspect, the invention aims at providing an improved method for making said barrier screen. The invention finally aims at providing an improved dike body having a greater strength and wherein draining of soil material can be adequately prevented.
According to a first aspect, the invention provides a cutter for making a barrier screen in a dike body for preventing transport of soil particles, said cutter comprising: —a part that is oriented vertically when in use and that comprises a supply device for supplying to soil material of said dike body a binder for binding soil material that has been cut by said cutter, said vertically oriented part at a lower portion thereof being provided with chisels for cutting said soil material during a downward movement of said cutter; —as well as a part that is horizontally oriented when in use and that extends at both sides of said vertical part and wherein said parts that are provided at both sides comprise cylinders that are rotatable about a horizontal rotation axis and wherein said cylinders are provided with ground cultivating members for mixing soil material that has been machined by said chisels and said ground cultivating members. This cutter allows one to simply obtain an improved dike body.
Preferred embodiments of the invention will be mentioned hereafter, advantages of these embodiments becoming clear from the description.
In the present description and claims the terms “soil” and “ground” are used interchangeably. For example, the terms “ground cultivating members” and “soil cultivating members” are used interchangeably, as well as the terms “ground” and “soil” as such.
So as to obtain a fast and effective soil cultivation it is preferred that said ground cultivating members are provided on the cylinders' surface spiral wound.
A fast and efficient mixing is obtained when the supply device feeds the binder towards the horizontal cylinders.
A good cutting of the soil material is obtained when the chisels are shaped as a rotating milling head.
A simple but very efficient embodiment consists of a cutter wherein the ground cultivating members are provided on the cylinders in a single pitch.
The cutter may essentially be fed substantially linearly vertically into the ground, when at both sides of said vertical part cylinders are provided that, when in use, rotate in opposite directions.
A faster vertical displacement is attainable when the cutter comprises two sets of horizontally oriented parts, wherein at both sides of said vertically oriented part two horizontally oriented parts are positioned. The mixing and cutting of the soil material by means of the horizontally oriented parts will be provided by both said parts.
A homogeneous soil material is obtained when the ground cultivating members are embodied for at least partly mixing and cutting said soil material. Preferably, both said means ensure both treatments.
The cutter preferably comprises a binder contained for containing a binder and a supply pipe from said contained to said supply device.
According to another aspect, the invention provides a method for making a barrier screen in a dike body for preventing transport of soil particles, by using a cutter according to the invention, said barrier screen being in a substantially standing position and extending in a longitudinal direction of said dike body, comprising the step of urging the cutter substantially vertically into the dike body and mixing soil material of said dike body with binder.
An effective method is embodied by repeatedly urging the cutter into the dike body and mixing soil material of said dike body with binder at at least partially staggered positions for making a continuous barrier screen of partially overlapping columns inside said dike body.
Preferably, the soil material of said dike body is milled to an average particle volume of less than 10 cubic millimeter of soil material, preferably less than 2 cubic millimeter, more preferably less than 1 cubic millimeter.
The invention further relates to a barrier screen in a dike body comprised of at least partially overlapping columns of soil material of said dike body and binder, obtained by means of a method according to the present invention.
By providing a barrier screen being embodied from a mixture of binder and soil that is already present in the dike body, supply and discharge of several components and building materials for making the barrier screen can be reduced. More in particular, by using the soil that is already present in the dike body, a barrier screen may be made in the dike body without firstly making a trench or urging a piling sheet in the dike body. Furthermore, the costs of such barrier screen are substantially less than the costs for making a steel sheet piping.
The mixture of soil and binder in the dike body can be used for providing the dike body material a firm, homogeneous and cohesive granular structure, that is to say a structure of mutually bonded grains. Such granular structure serves as the barriers screen.
The barrier screen comprises grains from the kind of soil that is present in the dike body adjacent the said barrier screen, said grains being mutually connected through said binder. The average grain size in said barrier screen may for example be less than one, less than two or less than ten cubic millimeter per grain. The kind of soil in said dike body adjacent said barrier screen may be homogeneous or layered, may comprise structures that are larger than the average grain size in said barrier screen. Due to the presence of the grains in said barrier screen a much firmer structure is obtained than compared with feeding the binder to a layered soil of a soil comprising larger structures than the present average grain size. Grains that are built from the soil and that are connected though said binder may provide a firmer structure. Such leads to an improved stability of the dike body.
The barrier screen preferably extends until a depth within the dike body through which, without the presence of the barrier screen, soil particles would be migrated through the flow of said seepage water, for example until a depth of one to ten meters below the dike body's surface at the position of said barrier screen. An additional advantage when strengthening sea dikes by means of the present invention, is that salinization of the landbased part of the dike is prevented since the amount of seepage water ca be reduced drastically.
The barrier screen is preferably embodied narrowly having a width of between 0.1 meter and one meter perpendicularly to the longitudinal direction of the dike body, for example between 0.4-0.7 meter. In the longitudinal direction the barrier screen preferably extends continuously along the total length of the dike. In case interruptions are provided in the dike, these preferably are provided only after for example at least ten or one hundred meters of continuous barrier screen.
According to an embodiment the top position of the barrier screen is at a distance below the surface of the dike body at the position of the barrier screen, for example 0.5-2 m below said dike body's surface. According to an embodiment, the barrier screen may be covered with a top layer of clay, sand or mud. Such top layer may be used for constructing a road.
According to an embodiment the binder may be cement, bentonite, lime, toperete or fly ash (for example certified fly ash), or a mixture thereof with another component, for example more than one chosen from cement, bentonite, lime, toperete and fly-ash.
According to an embodiment the binder is a grout, for example obtained from a mixture of cement, water and optionally ad-mixed with an additive and excipients, wherein said grout is mixed with said soil of said dike body for making a barrier screen.
Depending on practical considerations, it may be chosen to position the barrier screen ate a water based part of the dike body (between the base of the dike and the water), or at a land-based part of the dike body (at the side of the dike that is directed away from the water) or at a middle portion of the dike body, erecting from the surroundings and substantially comprising a soil material. When the barrier screen is positioned at a water side part of the dike, use is preferably made of a substantially water tight barrier screen. Without preventing seepage water to flow through the dike body, accumulation of water and salinization of the hinterlands can be prevented.
Another embodiment comprises the step of positioning the barrier screen at the landbased part of the dike body. Such preferably comprises the application of a water-permeable barrier screen. As a consequence, part of the seepage water can flow through or may be absorbed by said barrier screen, whereas transport of soil particles is prevented by the presence of said screen or is at least filtered. Since the barrier screen will be embodied as a water-permeable screen any seepage water will not accumulate in the dike body with the result that a drainage system is not necessary.
Another embodiment comprises the step of placing the barrier screen at a middle ground portion of said dike body. Preferably, but not obligatory, the barrier screen is made substantially watertight in this embodiment. The embodiment in the middle portion of the dike body (the so-called crown of top) is especially preferably in case of small and weak dikes, for example peat dikes. More in particular some peat dikes are small and usually only accessible at their top. According to an embodiment a small dike body may be embodied completely as a barrier screen as described in the present description in the case of a barrier screen forming part of a dike body.
The continuous barrier screen may preferably be embodied as a concatenation of columns, wherein said columns are positioned adjacent next to each other, and preferably such as to partially overlap so as to make the barrier screen extend continuously and parallel to the dike body. Adjacent columns may be made column-wise by means of relatively lightweight apparatuses.
By positioning the columns of said barrier screen in an overlap open spaces, forming tunnels through which seepage water and ground particles may flow, in between adjacent columns are easily prevented. The columns are preferably positioned substantially upright. According to an embodiment the top of the columns is positioned below ground level. According to an embodiment the columns have a length of at least one meter in the longitudinal direction and a width of at least 0.4 meter perpendicularly thereto.
The invention further relates to a method for making an barrier screen in a dike body for preventing transport of soil particles, said barrier screen being oriented substantially standing upright and extending in a longitudinal direction of said dike body, in said method the barrier screen being comprised of mixing soil material that is present in said dike body before commencing the step of making said barrier screen mechanically with a binder. Said mixing for example may be performed in situ at a depth below the surface of said dike body.
According to the invention the soil material that is already present in said dike body before commencing the step of making the barrier screen is converted in grains by means of cultivating methods, for example by means of grinding, milling and/or cutting, and said grains are mutually connected by means of said binder. Said mixing can be performed simultaneously with the step of making said grains.
Preferably, the soil (i.e. the dike body material) is machined such that grains (also comprising grain-like particles) are obtained with an average volume of less than 1 or 2 cubic millimeter per grain. The size distribution of grains is preferably substantially homogeneous. By machining the soil of the dike body until grains are obtained and binding same with a binder, the barrier screen becomes sufficiently firm. In case of peat material, this has the additional advantage that the layered structure of said peat has disappeared in situ.
According to an embodiment the binder is added as a powder from a binder container to the soil. The dike material's intrinsic humidity enables one to mutually bind the grains by adding dry powdered binder.
According to an embodiment the binder comprises cement, bentonite, lime, toperete or fly-ash, or a combination thereof. According to another embodiment, the binder is a grout, for example as obtained from a mixture of cement that has been moistened with water and optionally added aggregates and additives wherein grout is mixed with the soil material so as to yield a barrier screen. In addition to that, the binder may be a liquid. This has the advantage that the binder may be added to a non-humid soil material for making a barrier screen; such (semi)liquid binder ca=n be pumped relatively easy from a binder container.
According to an embodiment the binder is added from a pre-determined depth and lower into the soil, for example by applying a supply device. This allows one to save space above said barrier screen for constructions like roads and gates.
According to an embodiment the barrier screen is made by means of a cutter that is provided with moving chisels for cutting the soil material, according to which method said cutter is moved through the dike body's machined soil material along a range of positions in the barrier screen to be made, and wherein the binder is injected into the soil through which the chisels are moved. As a consequence, any preliminary removal of soil material is not required. As a consequence, any soil depth-dependent differences in the dike body adjacent the barrier screen are obtained in the barrier screen at said same depths. The binder is added together with the step of cutting and remains mixed with the machined soil at the positions the cutter has performed its cutting actions and subsequently has been removed from. By such local cutting action, a homogeneous grain structure is obtained that is less diverse than when injecting a suspension or when pressing a binder into said soil as such. De cutter may provide a simultaneous step of a mechanical mixing of binder and soil.
Hence, the barrier screen's shape and position is determined by the movement of the cutter. According to an embodiment the cutter is continuously displaced in a vertical manner in a series of consecutive and partially overlapping columns in the longitudinal direction of the dike body, that is to say in the range of positions of the barrier screen to be made.
According to an embodiment of the present invention the cutter comprises a rotor that is driven rotatably around a rotation axis. Chisels are provided at the circumference of the cylinder, for example along a spiral wound path. In such case, the cylinder may be entered into the soil with its cylinder axis in the longitudinal direction of the barrier screen, such that the diameter of said cylinder essentially determines the thickness of said barrier screen and wherein the length of said cylinder determines the length of said column of the barrier screen, or part of said length, if the cutter comprises a plurality of such cylinders, said cylinders are positioned mutually in line.
Providing a cutter that is provided with moving chisels for machining the soil, the cutter may be moved substantially vertically downwards into the soil of the dike body along a trajectory, i.e. a range of positions, that are positioned at the barriers screen to be made and wherein the binder is injected into the soil that is machined by said chisels. The may provide a cutting and/or mixing acion and are provided for cutting soil material and mechanically mixing the binder and said machined soil material.
By applying a 3D-positioning system the cutter may be positioned such for making each of the columns of the barrier screen.
The barrier screen may be water tight or (semi) liquid permeable. Such can be controlled by setting the amount of binder that is added per unit volume of soil, and the kind of binder. The required amounts and the kind of binder may be determined experimentally. Prior to placing the barrier screen a first step may comprise the step of determining the required permeability of said barrier screen. By taking a sample of said dike body's soil material, or a comparable soil material, it may be determined experimentally if, after having added different amounts of binder, the required permeability has been obtained. In case of standard types of soil material, the results may be entered into (and retrieved from) a table, such that a choice of a required amount of binder ca be determined without the need of performing further experiments.
For example, in case the soil is a clay, peat or a soil without bearing capacity, said mixture may comprise 100 kg binder per m3 soil, for obtaining a substantially watertight barrier screen. According to an embodiment, at least 90% of the amount of seepage water is restricted compared to a dike body without a barrier screen. For example, in cases where the mixture comprises 60 kg binder per m3 soil, the barrier screen may have a porous structure, comparable to clay and comprising small pores. These pores are relatively small compared to for example the width of a barrier screen column, with the consequence that part of the seepage water may still flow through the barrier screen, but wherein transport of soil particles is prevented. Preferably, the barrier screen has a permeability of between 0-0-10-9 m/s, according to Darcy's law, but this permeability may be altered, depending on the circumstances. Furthermore, since the barrier screen has a clay like structure, the screen may be flexible. As a consequence, the screen may move with the soil without tearing.
The invention further relates to a cutter for making a barrier screen in a dijk, provided with a binder container, and a supply device embodied for feeding binder from said binder container to a position near the chisels during milling and cutting.
It is mentioned that the technical measures relating to the dike also may be implemented advantageously as such as well in dike bodies comprising different configurations, i.e. the individual measures may be de isolated from the context used above and may be applied as such, optionally applying one or more measures mentioned above.
These and other aims and favorable aspects become clear from the description of examples and figures to follow.
a-c shows schematic views of a dike body according to
It is mentioned that the figures depict schematic views of preferred embodiments of the present invention, being provided as non-limiting examples. In the figures, the same or corresponding parts are denoted by the same reference numbers.
In
In
The barrier screen may be provided in the inner dike part 6, the oter dike part 5 or the middle portion 7. It is also possible that a plurality of barrier screens are provided in the dike body, in the same or different parts of the dike body. The barrier screen serves as a means for preventing transport of soil particles. To that end the barrier may in itself hinder the flow of seepage water, or may at least partly hinder the transport of the soil particles that are transported by the flow of seepage water, even in cases where the flow of seepage water itself is not substantially hindered. Preferably, the barrier screen extends until a depth in the dike body 4 where seepage water 33 flows together with particles 34, for example a depth between about 4 meter and about 10 meter.
According to an embodiment wherein the barrier screen 11 is positioned in an outer dike part 5 (
According to an embodiment wherein the barrier screen 11 is positioned in the crown of the dike (
According to an embodiment wherein the barrier screen 11 is positioned in the inner dike part 6 (
According to an embodiment the barrier screen extends in a height direction that does not higher than a distance below the dike's surface level 14. A top 31 of said barrier screen 11 may be positioned below the surface of the dike body, for example 0.5-2 m below said surface.
The binder that is used for being mixed with the soil material of said dike body for making the barrier screen column is preferably chosen from a cement, bentonite, lime, toperete or fly ash (toperete is a by-product from the paper industry and that may be used as a binder).
The invention further relates to a method for making a barrier screen 11 in a dike body 4 for preventing transport of soil particles. The barrier screen 11 is made by in situ mixing of soil of said dike body 4 mechanically with binder at the position where the barrier screen is to be made. To that end, soil is milled substantially at the same time of mixing same, with the consequence that the soil is converted into grain like particles with a substantially homogeneous particle size distribution.
The binder connects the grain like particles so as to obtain a rigid structure making the barrier screen.
In the embodiment according to
By said mixing a somewhat raised surface may be obtained at the position of the barrier screen 11. According to an embodiment the soil is pressed, for example by driving a heavy machine over said raised surface or by positioning a weight on it. Said pressing increases the rigidity of the barrier screen 11.
The barrier screen 11 may be water tight or liquid permeable. For example, when the soil of said dike body 4 comprises clay-like, peat-like or no load-bearing surface it may be mixed with 100 kg per m3 binder so as to obtain a substantially water tight barrier screen 11 such that about at least 90% of flowing seepage water is retained by said barrier screen 11, comprised with a situation without a barrier screen 11. If in such case for example 60 kg per m3 binder is added to the soil material of said dike body a substantially water permeable barrier screen 11 may be obtained. The liquid permeability of said barrier screen 11 may for example be between about 0-0-10-9 m/s according to Darcy's law, such that migration of soil particles through the dike body 4 from the water area to the landbased part 2 due to the seepage water is hindered effectively.
In
At the side of said lying part 20 rotating cylinders 25 are provided. When in use, said laying part 20 is positioned substantially along the dike body 4. At their circumference, the cylinders 25 are provided with soil cutting chisels 26 that are provided at a spiral path along the circumference, and that serve as cutters and mixers for cutting the soil and mechanically mixing the binder 15 that is injected with the cut soil so as to obtain a barrier screen column 12. As shown in this Figure the end part 22 of the supply device 21 ejects the binder from a central part of the standing part towards the soil cutting chisels 26. According to an embodiment additional additional mixing paddles may be provided on the cylinder that do not provide for a cutting of the soil.
When in use, the cylinders 25 are rotated mechanically around the cylinder axis. This is provided both for cutting the soil as for mixing the machined soil and the binder. The cylinders 25 are guided vertically through the cut soil in a horizontal position.
At the end of the standing part 19 rotating cutter head 23 is provided. For illustration purposes, in the figure the cutter head is detached from the figure, But in practice the cutter head is at a lowermost position longitudinally with respect to the standing part 19. When in use, the cutter head 23 makes its way downwardly between the cylinders 25 of said cutter 17, for example vertically downward, through the dike body's 4 soil. To that end, the cutter head 23 is provided with moving chisels 24 for cutting and milling the soil.
Since the cutter 17 is provided with rotating cylinders 25 comprising cutting and mixing chisels 26 the making of large clumps of soil that do not contain any amount of binder is prevented. Such clumps would deteriorate the barrier screen's strength. The risk of such clumps would exist if the binder would only be injected into the soil and the soil would not be converted into grains and be mixed, for example by means of said mixing chisels. After the binder in a column 12 has been mixed sufficiently with soil, the cutter 17 moves upwards after which it is used for consecutively making another column 12 of said barrier screen. To that end, the cutter 17 is positioned such as to make overlapping columns 12 along the dike body 4, that together make the barrier screen 11.
Positioning the cutter 17 is preferably obtained by means of a 3D positioning system, for example by applying GPS positioning.
Although a single rotor is shown in the Figure, that provides both mixing and cutting, separate rotors could be provided that are positioned above each other and that respectively would be used for cutting and mixing.
The invention also relates to a device 32 according to
The method and device are described for improving dikes, wherein a longitudinal barrier screen 11 is made in the soil for preventing he transport of soil particles. A comparative method and device may be used for other aims as well, for example for mixing a block of soil with a binder, wherein such block of soil may be much thicker than a barrier screen. Such block may for example be used as a foundation for building purposes. Also, the method may be used for immobilizing or fixating contaminating particles in the ground. To that end, the columns may be made in two horizontal continuous directions, for example in the shape of a rectangle as seen from above. Also, the method may be made in a series of parallel, preferably partially overlapping, lanes. It that case a rigid block of soil is obtained, wherein said block is obtained by mixing soil already present in situ mechanically below surface level with a binder.
For obtaining a wide barrier screen 11 a plurality of lanes or rows of columns may be required.
It will be clear to a man skilled in the art that the invention is not limited to the embodiments as described above and as depicted in the drawing. Many embodiments are possible within the scope of protection conferred by the appending claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| NL 2013332 | Aug 2014 | NL | national |
