JP4589797B2 - Method for reducing water permeability of ground and injection pipe device - Google Patents

Description

  The present invention is used to reduce the water permeability of the ground for the purpose of preventing spring water in the sand ground or gravel ground or improving the soft ground, in other words, a method of forming a low water permeable layer, and the implementation of the method. It belongs to the technical field of injection tube devices.

  Conventionally, as countermeasures such as prevention of water leakage from a defective part of a retaining wall or prevention of spring water from the bottom of excavation in excavation work where the water-permeable sand ground or gravel ground continues deep into the ground, In many cases, a chemical solution injection method as disclosed in Patent Documents 1 and 2 is implemented. As the chemical solution material to be injected, a material mainly composed of water glass or a material mainly composed of cement is mainly used. The construction methods of Patent Documents 1 and 2 are characterized in that two liquids are brought into contact before injection and penetrated into the ground using the time until solidification.

  The water stopping method disclosed in Patent Document 3 below is characterized in that two or more types of aqueous solutions that generate insoluble precipitates by mixing are separately injected into the ground. It is described that the two or more types of aqueous solutions are calcium salt aqueous solution and carbonate and / or carbonic acid aqueous solution.

  The following Patent Documents 4 and 5 relate to the inventions of the present inventors and are patents relating to the application of the present applicant. Two types of aqueous solutions are separately injected into the ground, mixed in the ground and reacted to generate two or more fine water-insoluble precipitates in the ground, reducing the water permeability of the ground. And

  The inventions of Patent Documents 6 and 7 below relate to a chemical solution injection method, but are characterized in that two or more improved bodies are created in the ground using a plurality of packers.

Japanese Patent No. 3324012 Japanese Patent Laid-Open No. 11-36280 JP 2000-104066 A Japanese Patent No. 3600892 Japanese Patent No. 3644356 Japanese Patent No. 3313351 Japanese Patent No. 3500444

The chemical solution injection method disclosed in Patent Documents 1 and 2 uses a material containing water glass as a main component or a material containing cement as a main component as a chemical solution material, and the two solutions are brought into contact and solidified before injection. This is a method of infiltrating into the ground using the time until, and the injection principle is different from that of the present invention. Since the injection range is as narrow as 1 to 2 m around the injection hole, there is a problem that an extremely large number of injection holes are required.
Although the water stop method disclosed in the above-mentioned Patent Document 3 can be noted that two or more kinds of aqueous solutions are separately injected into the ground, no specific description is given of the injection means.

  Since the above Patent Documents 4 and 5 relate to the inventions of the present inventors, the injection principle is partially shared with the present invention. However, since the structure is such that only one layer of fine, hardly water-soluble precipitate is generated in the ground, the two kinds of solutions injected into the ground remain in contact with each other without being mixed and reacted. There is a large proportion of the amount of solution that penetrates into the ground and remains. In order to reduce the water permeability of the ground accordingly, it is necessary to inject a large amount of solution, which is uneconomical and prolongs the construction period. In addition, when a hydraulic pressure difference is generated above and below the generated low water permeable layer, a local hydrodynamic gradient acts because the layer thickness of the low water permeable layer is thin, but the durability of the low water permeable layer against the pressure ( There is a concern that the pressure resistance is low.

  Although the above Patent Documents 6 and 7 are chemical solution injection methods, it can be noted that two or more improved bodies are created in multiple stages in the ground using a plurality of packers. However, each method is a method in which two kinds of solutions are brought into contact before injection and injected into the ground through a single injection tube. In order to solve the problem that the injection range is narrow, a large improved body It is nothing but the content of creating an improved body according to the ground.

The object of the present invention is to inject two or more kinds of aqueous solutions that easily penetrate into the sand ground or gravel ground into the ground separately and react in the ground so that they are widely fine in the ground and hardly soluble in water. This is a method of generating precipitates and reducing the water permeability of the ground, in particular, increasing the contact efficiency of the two types of solutions injected into the ground, mixing and penetrating into the ground without reacting. A method for reducing the water permeability of the ground, which can reduce the ratio of the amount of solution, relatively reduce the amount of solution injection required to lower the water permeability of the ground, improve the economy, and shorten the construction period. And providing an infusion tube device for use in performing the method.
The next object of the present invention is to form a plurality of layers of fine and sparingly water-soluble precipitates in the ground and combine them to form a layer that lowers the water permeability of the ground to a substantially large thickness, thereby reducing the low water permeability. Even when a local hydraulic gradient occurs due to a difference in water pressure between the upper and lower layers, a method for creating a stable low water-permeable layer with high durability (pressure resistance) against pressure, and injection used to implement the method To provide a tube device.

As a means for solving the above-described problems of the prior art, a method for reducing the water permeability of the ground according to the invention described in claim 1 is:
The injection hole 18 is excavated in the ground 1, the injection tube device 2 is inserted into the injection hole 18, and the two types of solutions X and Y are separately injected from the ground through the injection tube device 2 and injected. In the method of reducing the water permeability of the ground by mixing and reacting the two types of solutions X and Y in the ground to generate fine and hardly water-soluble precipitates 8 in the ground 1,
The injection tube device 2 includes two injection tubes 10 and 11 for separately feeding two types of solutions X and Y, and a plurality of partition means 6 for partitioning the injection holes 18 and the injection tubes 10 and 11 from each other in the vertical direction. in comprising, vertically two into the ground in each position of the plurality of inlet leg 7A~7D partitioned solution X, and configured to inject at staggered permutations Y up and down by the partitioning means 6,
The injection pipe device 2 installed in the injection hole 18 is divided into two injection pipes after partitioning the injection hole 18 and the injection pipes 10 and 11 into a plurality of injection sections 7A to 7D in the vertical direction by the partition means 6. the two solutions X into the ground, the Y respectively injected horizontally staggered permutations vertically to each position on the inlet leg 7A~7D through 10, 11,
The two types of solutions X and Y are mixed and reacted in the ground 1 to generate a plurality of fine and hardly water-soluble precipitates 8 in the ground, thereby reducing the water permeability of the ground.

The method of reducing the water permeability of the ground according to the invention described in claim 2
The injection hole 18 and the pumping hole are excavated at a certain interval in the ground 1, the injection pipe device 2 is inserted into the injection hole 18, the pumping pipe device 3 is inserted into the pumping hole, and each is installed. Two kinds of solutions X and Y are separately injected from the ground through the injection pipe device 2, and the groundwater is pumped by the other pumping pipe device 3 to form a local hydrodynamic gradient θ in the ground, thereby generating a groundwater flow. In the method of reducing the water permeability of the ground by mixing and reacting the injected two types of solutions X and Y in the ground 1 to generate fine and hardly water-soluble precipitates 8 in the ground.
The injection tube device 2 includes two injection tubes 10 and 11 for separately feeding two types of solutions X and Y, and a plurality of partition means 6 for partitioning the injection holes 18 and the injection tubes 10 and 11 from each other in the vertical direction. to provided to the partitioning means 6 by the ground during 1 to each position of the plurality of inlet leg 7A~7D partitioned upper and lower two solutions X, configured to inject at staggered permutations Y up and down,
The injection pipe device 2 installed in the injection hole 18 is divided into two injection pipes after partitioning the injection hole 18 and the injection pipes 10 and 11 into a plurality of injection sections 7A to 7D in the vertical direction by the partition means 6. injected horizontally respectively in each position of the inlet leg 7A-7D 2 kinds of solutions X into the ground in 1, in a staggered permutations of Y in the vertical through 10, 11,
In the pumping pipe device 3 installed in the pumping hole, the groundwater in the ground 1 is pumped up to form a local hydrodynamic gradient θ in the ground to generate the groundwater flow.
The two types of solutions X and Y injected into the ground 1 are mixed and reacted in the ground to generate a plurality of fine, water-insoluble precipitates 8 in the ground 1 to reduce the water permeability of the ground. It is characterized by.

The invention described in claim 3 is a method for reducing the water permeability of the ground described in claim 1 or 2,
The two types of aqueous solutions X and Y injected into the ground are an aqueous solution containing +2 or +3 valent iron ions and an aqueous solution that oxidizes the aqueous solution.

The invention described in claim 4 is a method for reducing the water permeability of the ground described in claim 1 or 2,
The two types of aqueous solutions X and Y injected into the ground are a ferrous sulfate aqueous solution (dissolved iron) and a potassium permanganate aqueous solution (oxidant).

The injection tube device 2 according to the invention described in claim 5 is:
It is inserted into the injection hole 18 excavated in the ground 1 and two kinds of solutions X and Y are separately injected, and the two kinds of solutions X and Y are mixed and reacted in the ground to make fine water in the ground 1. An infusion tube device that generates poorly soluble precipitates 8 and lowers the water permeability of the ground,
Two injection pipes 10 and 11 for separately feeding two kinds of solutions X and Y to be injected into the ground 1 and injecting them into the ground, and one water supply pressure pipe for expanding the packer rubber 6c as the partitioning means 6 12 is the main part,
At the mounting position of the packer rubber 6c, there are provided a packer cylinder 6a that covers the outer periphery of each tube, and a cylinder head 6b that passes through and fixes each tube. Is connected to the water supply pressure pipe 12 passing through the packer cylinder 6a.
The two injection pipes 10 and 11 have either one of two types of solutions X and Y for each position of the injection sections 7A to 7D partitioned by the partition means 6 composed of the packer cylinder 6a and the packer rubber 6c. A plurality of injection ports 13 are arranged in the vertical direction only in the injection pipes 10 or 11 and in different injection pipes at different positions in the vertical direction, and the tips of the respective pipes are closed. Are each characterized.

In the present invention, two types of aqueous solutions X and Y are separately poured into the ground 1, mixed in the ground, and reacted to generate fine and hardly water-soluble precipitates 8 in the ground 1. This is a method for lowering the property (forming a low water permeable layer), so the injection range is wider compared to the conventional methods in which the two liquids are brought into contact before injection, for example, as described in Patent Documents 1, 2, 6 and 7 above. The low water permeable layer 8 can be formed efficiently. Therefore, the number of injection holes 18 can be increased to reduce the number of injection holes 18 and the work can be carried out efficiently and economically, and the construction period can be shortened.
In addition, since the two types of solutions X and Y are injected in a staggered permutation into the plurality of injection sections 7A to 7D partitioned vertically, the solution injected into the intermediate injection section is injected into the upper and lower injection sections. The opportunity and degree of mixing and reaction with different types of solutions are high, and the contact efficiency of the two types of solutions X and Y injected into the ground 1 is increased. Therefore, the ratio of the amount of the solution that permeates into the ground without remaining mixed and reacts is greatly reduced, and the amount of solution injection required to relatively reduce the water permeability of the ground can be reduced.

  In the present invention, a plurality of fine water-insoluble precipitates 8 are formed on the upper and lower sides of the ground 1 and combined to form a substantially low thickness water-permeable layer. Even when a local hydrodynamic gradient θ acts, the durability (pressure resistance) against the pressure is high and stable.

The injection tube device 2 includes two injection tubes 10 and 11 for separately feeding two kinds of solutions XY, and a plurality of partitioning means 6 for partitioning the injection hole 18 up and down. It is configured to inject two types of solutions X and Y into the ground 1 from the plurality of injection sections 7A to 7D, which are alternately arranged,
The injection tube device 2 installed in the injection hole 18 is divided into a plurality of injection sections 7A to 7D in the vertical direction by the partition means 6 and then into the ground 1 from each of the injection sections 7A to 7D. The solutions X and Y are injected in the horizontal direction in a staggered permutation, and the two types of solutions X and Y are mixed and reacted in the ground to form fine and hardly water-soluble precipitates 8 in the ground 1. Multiple layers are generated to reduce the water permeability of the ground 1.

The injection pipe device 2 for carrying out the above-described method for reducing the water permeability of the ground 1 is as follows:
Two injection pipes 10 and 11 for separately feeding two kinds of solutions X and Y to be injected into the ground 1 and injecting them into the ground, and one water supply pressure pipe for expanding the packer rubber 6c as the partitioning means 6 12 is the main part.
At the mounting position of the packer rubber 6c, there are provided a packer cylinder 6a that covers the outer periphery of each tube, and a cylinder head 6b that penetrates and fixes each tube, and the packer rubber 6c is placed on the outer periphery of the packer cylinder 6a. The packer rubber 6c is connected to the feed water pressure pipe 12 passing through the packer cylinder 6a.
The two injection tubes 10 and 11 include only one of the two kinds of solutions for each position of the injection section partitioned by the partition means 6 composed of the packer cylinder 6a and the packer rubber 6c, and A plurality of injection ports 13 are arranged in a vertically distributed manner in different injection pipes 10 or 11 for each position of different injection sections 7A to 7D in the vertical direction, and the tips of the pipes 10, 11, and 12 are closed.

In the following, the present invention will be described with reference to illustrated embodiments.
As an embodiment of the invention according to claim 2, FIG. 1 shows a pair of an injection pipe device 2 (so-called recharge well) and a pumping pipe device 3 (pumping well) with a certain interval L in the construction target ground 1. The construction drawing installed in relation is shown.
From the injection tube device 2, two types of first aqueous solution X (for example, ferrous sulfate aqueous solution) and second aqueous solution Y (for example, potassium permanganate aqueous solution) are supplied to different injection tubes and injection pumps described later, respectively. Inject separately using 4 (or by gravity without using an infusion pump). From the other pumping pipe device 3, groundwater is pumped by a pumping pump 5, thereby generating a local hydrodynamic gradient θ in the groundwater in the ground, and the penetration of the two aqueous solutions X and Y into the ground. Promoting mixing and reaction is the same as the inventions of Patent Documents 4 and 5 above.
However, the method for reducing the water permeability of the ground according to the present invention is performed by installing the injection pipe device 2 (recharge well) and the pumping pipe device 3 (pumping well) in a paired relationship as shown in FIG. Not limited to content. The injection pipe device 2 and the pumping pipe device 3 are installed in a pair to create a local hydrodynamic gradient θ in the groundwater in the ground, and promote the permeation, mixing and reaction of the two types of aqueous solutions X and Y. Although it is a preferred embodiment, depending on the implementation conditions and purpose, the water permeability of the ground can also be obtained by installing only the injection tube device 2 and unilaterally injecting the two types of aqueous solutions X and Y. The object of lowering can be achieved (the invention according to claim 1).
Moreover, as two types of aqueous solutions to be injected, a combination of an aqueous solution containing +2 or +3 valent iron ions and an aqueous solution that oxidizes this, specifically, a ferrous sulfate aqueous solution (dissolved iron) and potassium permanganate. An aqueous solution (oxidant) can be used.

  In FIG. 1, the injection tube device 2 comprises four injection sections 7A to 7D in which the injection holes are partitioned in the vertical direction by five partitioning means 6 having the configuration described later, as illustrated in an enlarged view in FIG. The injection tube device 2 injects two kinds of solutions X and Y toward the ground 1 in each of the injection sections 7A to 7D in the horizontal direction in a staggered permutation. On the other hand, the pumping pipe device 3 sucks and pumps groundwater, efficiently meets the two kinds of solutions X and Y in the ground 1, mixes and reacts them, and deposits that are fine and hardly soluble in water in the ground 1. 8 is a conceptual diagram of a method for reducing the water permeability of the ground 1 by generating a total of three low water permeability layers according to No. 8.

3 to 6 specifically show the configuration of the main part of the injection tube device 2 as an embodiment of the invention according to claim 5. This will be described below.
First, FIG. 3 shows the relationship between a total of five packer portions 6 which are partition means constituting the injection tube device 2, and four injection sections 7A to 7D which partition the injection holes in the ground in the vertical direction by the packer portions 6, and The whole figure of the structure relevant to the two injection | pouring pipe | tubes 10 and 11 which deliver two types of solutions X and Y separately is shown. As an example, the length of one packer portion 6 is 320 mm, the length of one injection section 7 is about 670 mm, and the length is one pitch.
FIG. 3 also shows that one of the two injection pipes 10 and 11 has reached the lowest injection section 7D, while the other one injection pipe 11 is the next higher injection. The structure which has stopped in the section 7C is shown. This is a necessary configuration for injecting two types of solutions X and Y.

FIG. 4 shows an enlarged view of the configuration related to the upper and lower two packer portions 6 and 6 and one injection section 7 partitioned by them. The packer portion 6 is composed of a rigid stainless steel cylinder 6a, a cylinder head 6b, and a packer rubber 6c (see FIG. 6 for details) installed on the outer periphery of the cylinder 6a. The two injection pipes 10 and 11 are piped so as to penetrate the cylinder head 6b, and the cylinder 6a covers the outer periphery thereof. Incidentally, the outer diameter of the cylinder 6a is about 80 mm.
In the one injection section 7, a plurality of injection ports 13 for pouring only one of the two types of solutions X and Y into only one injection tube 10 or 11, as an example. A large number of apertures are provided with a size of 5 mm and distributed in a single row or a plurality of rows in the circumferential direction at a pitch of 25 mm in the tube axis direction.

FIG. 5 further shows that the injection pipe device 2 includes, in addition to the two injection pipes 10 and 11, a single water supply pressure pipe 12 for supplying pressure water for expanding the packer rubber 6c as a partitioning means. Shows the configuration. The feed water pressure pipe 12 is also piped in a configuration penetrating the cylinder head 6b. Each of the two injection pipes 10 and 11 and the one feed water pressure pipe 12 is piped by connecting the necessary points with pipe joints. The feed water pressure pipe 12 is connected to the packer rubber 6c on the outer periphery of the cylinder by a branch joint 17 at a right angle at the position of each packer portion 6.
The cylinder 6a and the cylinder head 6b of the packer portions 6 and 6 adjacent to each other in the vertical direction are firmly connected in series by a connection wire 16 using a connection ring 15a as a connection tool and a spring snap 15b.

  FIG. 6 shows the details of the structure of the lowermost packer unit 6. The cylinder 6a of the packer portion 6 has its upper and lower ends closed by a cylinder head 6b. The packer rubber 6c is swelled at the upper and lower positions on the outer periphery of the cylinder 6a with bands so as to be able to expand toward the hole wall of the injection hole 18 (hole inner diameter is about 100 mm) excavated in the ground, and the middle part expands. Installed in configuration. Since the cylinder 6a has high rigidity, the packer rubber 6c swells only outward and exhibits a partitioning effect.

When the method of the present invention is carried out using the injection pipe device 2 having the above-described configuration, first, as shown in FIG. 7A, an injection hole 18 is first excavated in the ground 1 to prevent the hole wall from collapsing. A well structure with a perforated pipe (not shown) is used. The injection tube device 2 is inserted into the injection hole 18 and installed (position is fixed). And the water supply pump apparatus (illustration omitted) prepared on the ground and the water supply pressure pipe 12 of the said injection pipe apparatus 2 are connected, the water pressure adjusted suitably is sent to the water supply pressure pipe 12, and the packer rubber 6c of each packer part 6 is sent. The injection hole 18 is partitioned by expanding. Since the packer rubber 6c of each packer part 6 is expanded equally and synchronously, injection sections 7A to 7D in which the injection holes 18 are partitioned in the vertical direction are formed.
After that, the two injection tubes 10 and 11 of the injection tube device 2 are connected to the two types of solution X and Y supply sources 20 and 21 (see FIG. 1), and the two types of solutions X and Y are separated. The two kinds of injected solutions X and Y are mixed and reacted in the ground to generate fine and water-insoluble precipitates 8 in the ground, thereby reducing the water permeability of the ground.

  When three low water permeable layers are formed as in the above embodiment, even if a water pressure difference is generated above and below the three low water permeable layers, as shown in FIG. Compared to the conventional case of only one layer illustrated in FIG. 9, the structure is extremely gentle, and the durability against pressure (pressure resistance) is greatly increased and stable.

  Although the present invention has been described based on the illustrated embodiment, the present invention is not limited to the above embodiment. It is claimed that the present invention can be variously implemented in the form of design changes, modifications, and applications that are made by those skilled in the art as needed without departing from the spirit and technical idea of the present invention.

It is sectional drawing which showed the Example of the method of reducing the water permeability of this invention notionally. It is explanatory drawing which showed the injection | pouring aspect of two types of solutions. It is the elevation which showed the structure of the solution injection | pouring part of an injection tube apparatus. It is sectional drawing which showed the structure with which the packer part and injection | pouring area in an injection tube apparatus are related. It is sectional drawing which showed the structure with which the water supply pressure pipe and packer part in an injection tube apparatus relate. It is sectional drawing which expanded and showed the lowermost packer part to the injection tube apparatus. AD is sectional drawing which showed the implementation process of the method of reducing the water permeability of this invention notionally. It is a water pressure distribution figure explaining the effect of the method of reducing water permeability by the present invention. It is a water pressure distribution figure explaining the effect of one conventional low water permeability layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ground 2 Injection pipe apparatus 3 Pumping pipe apparatus X 1st aqueous solution Y 2nd aqueous solution 10, 11 Injection pipe 18 Injection hole 6 Partition means (packer part)
7A-7D Injection section 6a Cylinder 6c Packer rubber 13 Inlet

Claims (5)

An injection hole is excavated in the ground, an injection tube device is inserted into the injection hole, and two types of solutions are separately injected from the ground through the injection tube device, and the two types of injected solutions are injected into the ground. In the method of reducing the water permeability of the ground by mixing and reacting with in order to generate fine and hardly water-soluble precipitates in the ground,
It said injection tube device comprises two two injection tubes solution feeding separately, and a plurality of partitioning means for partitioning between the injection hole and the injection tube in the vertical direction, are partitioned vertically by the partition means the two solutions into the ground and configured to be implanted in a staggered permutations vertically for each position of the plurality of injection sections were,
The injection pipe device installed in the injection hole is divided into a plurality of injection sections in the vertical direction between the injection hole and the injection pipe by the partitioning means, and then in the ground for each position of each injection section through the two injection pipes. to two solutions were injected in a horizontal direction respectively staggered permutations vertically,
The two kinds of solutions are mixed and reacted in the ground to generate a plurality of fine and hardly water-soluble precipitates in the ground, thereby reducing the water permeability of the ground. How to make. The injection hole and the pumping hole are excavated at a certain interval in the ground, the injection pipe device is inserted into the injection hole, the pumping pipe device is inserted into the pumping hole, respectively, and the injection pipe is installed from the ground. Two types of solutions are injected separately through the device, groundwater is pumped up by the other pumping pipe device, a local hydrodynamic gradient is formed in the ground to generate a groundwater flow, and the two types of injected solutions are grounded. In the method of reducing the water permeability of the ground by mixing and reacting in the ground to generate fine and poorly water-soluble precipitates in the ground,
It said injection tube device comprises two two injection tubes solution feeding separately, and a plurality of partitioning means for partitioning between the injection hole and the injection tube in the vertical direction, are partitioned vertically by the partition means the two solutions into the ground and configured to be implanted in a staggered permutations vertically for each position of the plurality of injection sections were,
The injection pipe device installed in the injection hole is divided into a plurality of injection sections in the vertical direction between the injection hole and the injection pipe by the partitioning means, and then in the ground for each position of each injection section through the two injection pipes. to two solutions were injected in a horizontal direction respectively staggered permutations vertically,
In the pumping pipe device installed in the pumping hole, the groundwater in the ground is pumped to form a local hydrodynamic gradient in the ground, and the groundwater flow is generated.
The ground is characterized in that the two kinds of solutions injected into the ground are mixed and reacted in the ground to generate a plurality of fine and hardly water-soluble precipitates in the ground, thereby reducing the water permeability of the ground. To reduce water permeability.   The two types of aqueous solutions to be injected into the ground are an aqueous solution containing +2 or +3 valent iron ions and an aqueous solution that oxidizes the aqueous solution. The water permeability of the ground according to claim 1 or 2, How to lower.   The two types of aqueous solutions to be injected into the ground are ferrous sulfate aqueous solution (dissolved iron) and potassium permanganate aqueous solution (oxidant). How to lower. Inserted into the injection hole excavated in the ground, injecting two kinds of solutions separately, mixing the two kinds of solutions in the ground and reacting them, generating fine and poorly water-soluble precipitates in the ground An injection tube device that reduces the water permeability of the ground,
The main parts are two injection pipes for separately feeding two kinds of solutions to be injected into the ground and injecting them into the ground, and one supply water pressure pipe for inflating the packer rubber as a partitioning means.
At the attachment position of the packer rubber, a packer cylinder that covers the outer periphery of each tube and a cylinder head that penetrates and fixes each tube are provided, and the packer rubber is directed toward the hole wall of the injection hole on the outer periphery of the packer cylinder. Attached to the inflatable and connected to the water pressure pipe passing through the packer cylinder;
The two injection pipes are different only in one injection pipe of two kinds of solutions and different in the vertical direction for each position of the injection section partitioned by the partitioning means comprising the packer cylinder and the packer rubber. An injection tube device, wherein a plurality of injection ports are provided in an arrangement distributed in the vertical direction in different injection tubes for each position, and the tip of each tube is closed.

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