Electroosmosis grouting structure for improving uniform distribution of enzyme-induced mineralization products in shallow sand

Abstract

The invention relates to an electroosmosis grouting structure for improving uniform distribution of enzyme-induced mineralization products in shallow sand, which comprises a first electroosmosis grouting assembly and a second electroosmosis grouting assembly which are inserted into the shallow sand to be reinforced, the second electroosmosis grouting assembly is connected to the negative electrode of the direct-current stabilized power source through a wire, the first electroosmosis grouting assembly and the second electroosmosis grouting assembly each comprise at least one electroosmosis grouting pipe, and graphite carbon rings are arranged on the peripheries of the electroosmosis grouting pipes. The electroosmosis, grouting and slurry pumping functions are integrated in the electroosmosis grouting structure, and the diffusion distance of ions in the soil body is further increased, so that mineralized products of the soil body are distributed more uniformly; the problems that in the microbial mineralization technology, the carbonate crystal yield is gradually reduced along with the seepage path, so that the reinforcing effect of the soil body away from the grouting pipe in large-area foundation treatment is poor, and the overall reinforcing effect is not uniform are solved.

Description

Technical Field

[0001] The present invention relates to an electroosmotic grouting structure for improving the uniform distribution of enzyme-induced mineralization products in shallow sand, and relates to the application of the enzyme-induced mineralization-electroosmotic method in the field of soil reinforcement. Background Art

[0002] The enzyme-induced calcium carbonate precipitation technology (EICP) is an environmentally friendly and efficient geotechnical reinforcement method. In this technology, urease in soybean centrifugate decomposes urea into NH4 + and CO3 2− , and reacts with an externally introduced calcium source to generate calcium carbonate crystals with cementing effect, which cement adjacent soil particles and fill the soil pores to achieve the purpose of enhancing the soil strength. This technology has the advantages of environmental friendliness, simple reaction mechanism, low energy consumption, etc., and has broad application prospects in the reinforcement of poor soils. However, when using microbial slurry for grouting, a large amount of calcium carbonate quickly forms around the grouting pipe, resulting in a significant reduction in the porosity of the sand around the grouting pipe, poor injectability, and extremely limited slurry diffusion. As a result, the reinforcement effect of the existing soft soil microbial grouting reinforcement technology is often not ideal. In addition to the uncontrollable grouting reinforcement range, there is also the problem that the waste liquid after the mineralization reaction is difficult to recover, and the generated ammonia nitrogen compounds will greatly affect the surrounding environment. Summary of the Invention

[0003] In view of the deficiencies of the prior art, the technical problem to be solved by the present invention is to provide an electroosmotic grouting structure for improving the uniform distribution of enzyme-induced mineralization products in shallow sand, and to improve the problems of limited slurry diffusion distance and uneven distribution of cementitious substances existing in the traditional enzyme-induced mineralization grouting technology in shallow sandy soil strata.

[0004] To solve the above technical problem, the technical solution of the present invention is: an electroosmotic grouting structure for improving the uniform distribution of enzyme-induced mineralization products in shallow sand, including a first electroosmotic grouting component and a second electroosmotic grouting component inserted into the shallow sand to be reinforced. The first electroosmotic grouting component is connected to the positive electrode of a DC regulated power supply through a wire, and the second electroosmotic grouting component is connected to the negative electrode of the DC regulated power supply through a wire. Both the first and second electroosmotic grouting components include at least one electroosmotic grouting pipe, and a graphite carbon ring is provided on the outer periphery of each electroosmotic grouting pipe.

[0005] Preferably, each electroosmotic grouting pipe is composed of at least one grouting pipe. A plurality of grouting holes are axially provided on the circumference of each grouting pipe, and a wire groove parallel to the axis is provided on the outer periphery of each grouting pipe. A groove cover is provided on the notch of the wire groove, and a wire passing hole is provided on each groove cover.

[0006] Preferably, the number of graphite carbon rings on each grouting pipe is two, and the number of wire passing holes on each grouting pipe is also two.

[0007] Preferably, external thread connection segments are provided at both ends of the grouting pipe. The external thread connection segments of two coaxially adjacent grouting pipes are connected into one body through a sleeve. An internal thread is provided on the inner peripheral wall of the sleeve for screwing with the external thread connection segments of two coaxially adjacent grouting pipes respectively. And a notch parallel to the axial direction is provided on the circumference of the sleeve, making the sleeve as a whole in a shape similar to "C".

[0008] Preferably, the notch is aligned with the wire groove to facilitate the laying of wires.

[0009] Preferably, the wire is located in the wire groove. One end of the wire is connected to the corresponding graphite carbon ring through a wire passing hole, and the other end of the wire passes upward through the wire groove and is connected to the electrode of a DC regulated power supply. The connection between the wire passing hole and the wire is sealed with glass glue.

[0010] Preferably, the inner diameter of the graphite carbon ring is larger than the outer diameter of the grouting pipe. Rubber rings are filled between the upper and lower ports of the graphite carbon ring and the outer peripheral part of the grouting pipe and are sealed with glass glue.

[0011] Preferably, a conical plugging head with a pointed end facing downward is screwed on the bottom end of the bottommost grouting pipe of the electroosmotic grouting pipe.

[0012] Preferably, a pumping and grouting device is arranged inside the electroosmotic grouting pipe.

[0013] Preferably, pumping and grouting holes are provided on the circumference of the pumping and grouting device. The pumping and grouting holes communicate with the inner cavity of the pumping and grouting device. The top of the inner cavity communicates with a conduit. The top of the conduit is connected to a hose through a pneumatic joint. The hose is connected to an external grouting device or a pumping device; Sealing rings are fixedly provided above and below the pumping and grouting holes on the outer peripheral part of the pumping and grouting device for axially moving in contact with the inner peripheral wall of the grouting pipe and playing a sealing role.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention integrates the electroosmosis, grouting and pumping functions into the electroosmotic grouting structure, further improving the diffusion distance of ions in the soil, so that the distribution of mineralization products in the soil is more uniform, and solving the problems that in the microbial mineralization technology, the output of carbonate crystals gradually decreases with the seepage path, resulting in poor reinforcement effect of the soil far from the grouting pipe in large-area foundation treatment and uneven overall reinforcement effect.

[0015] The following further detailed description of the present invention will be made in conjunction with the accompanying drawings and specific embodiments. Description of the Drawings

[0016] Figure 1 It is a schematic diagram of the external structure of the electroosmotic grouting pipe in the embodiment of the present invention.

[0017] Figure 2Schematic diagram of the internal structure of the electroosmotic grouting pipe according to an embodiment of the present invention.

[0018] Figure 3 Schematic diagram of the structure of the pumping and grouting device according to an embodiment of the present invention.

[0019] Figure 4 Schematic diagram of the structure of the grouting pipe without a graphite carbon ring but with a wire installed.

[0020] Figure 5 Schematic diagram of the structure of the grouting pipe with a groove cover added.

[0021] Figure 6 Schematic diagram of the structure of the graphite carbon ring.

[0022] Figure 7 Schematic diagram of the structure of the casing.

[0023] Figure 8 Schematic diagram of the installation process of the electroosmotic grouting pipe.

[0024] Figure 9 Schematic diagram of the reinforcement principle according to an embodiment of the present invention.

[0025] Figure 10 Flowchart of the specific usage according to an embodiment of the present invention.

[0026] Figure 11 Flowchart of the steps of the reinforcement method according to an embodiment of the present invention. Detailed implementation mode

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0029] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0030] Such as Figures 1 to 11As shown in the figure, this embodiment provides an electroosmotic grouting structure for improving the uniform distribution of enzyme-induced mineralization products in shallow sand, including a first electroosmotic grouting component and a second electroosmotic grouting component inserted into the shallow sandy soil 1 to be reinforced. The first electroosmotic grouting component is connected to the positive pole of a DC regulated power supply via a wire 2, and the second electroosmotic grouting component is connected to the negative pole of the DC regulated power supply via a wire. Both the first and second electroosmotic grouting components include at least one electroosmotic grouting pipe, and graphite carbon rings 3 are provided on the outer peripheral parts of the electroosmotic grouting pipes as high-conductivity carbon ring electrodes.

[0031] The electroosmotic reinforcement technology forms an external electric field by inserting a cathode and an anode in the soil. Affected by the electric field, water in the soil is very easy to combine with cations to form hydrated cations and migrate to the place with low electric potential (cathode), thus achieving the effect of soil drainage and consolidation. In addition, the external electric field can make the ions in the soil migrate directionally. Therefore, the electroosmotic method can also achieve the directional enrichment and extraction of harmful elements such as cadmium and lead in contaminated soil, and has the dual functions of soil reinforcement and environmental remediation. Compared with traditional reinforcement methods, the electroosmotic technology has the advantages of being insensitive to the particle size distribution of soil particles, having a large reinforcement depth, and being simple in construction, and is a very promising soft soil reinforcement technology.

[0032] The present invention integrates the electroosmotic, grouting and pumping functions into the electroosmotic grouting structure, and uses the electroosmotic effect to drive the directional migration of Ca²⁺, CO3 2- and other ions in the EICP slurry, further increasing the diffusion distance of the ions, so that the mineralization products in the soil are more evenly distributed, and finally significantly improving the sand reinforcement effect.

[0033] It improves the problems of short slurry diffusion distance and uneven distribution of mineralization products during the grouting reinforcement process of the traditional EICP grouting device.

[0034] In the embodiment of the present invention, each electroosmotic grouting pipe is composed of at least one grouting pipe 4. A plurality of grouting holes 5 are arranged axially along the circumference of the grouting pipe, and wire grooves 6 parallel to the axis are provided on the outer peripheral parts of the grouting pipes. Slot covers 7 are provided at the openings of the wire grooves. The gap between the slot cover and the opening of the wire groove can be sealed with glass glue, and wire passing holes 8 are provided on the slot covers.

[0035] To prevent the wire from being damaged and the wire from being corroded by the slurry during the process of the grouting pipe sinking to the drilling position, a slot cover is provided for the wire groove.

[0036] In the embodiment of the present invention, the number of graphite carbon rings on each grouting pipe is two, and the number of wire passing holes on each grouting pipe is also two.

[0037] In an embodiment of the present invention, external thread connection sections 9 are provided at both ends of the grouting pipe. The external thread connection sections of two coaxially adjacent grouting pipes are connected into one body through a sleeve 10. An internal thread 11 is provided on the inner peripheral wall of the sleeve for screwing with the external thread connection sections of two coaxially adjacent grouting pipes respectively. And a notch 12 parallel to the axial direction is provided on the circumference of the sleeve, making the sleeve integrally in a shape similar to a "C".

[0038] According to the thickness of the shallow sandy soil layer, multiple sections of grouting pipes are connected through sleeves. At the same time, the corresponding wire lengths are selected according to the depths of different electroosmotic grouting pipes.

[0039] In an embodiment of the present invention, the notch is aligned with the wire groove, facilitating the laying of wires.

[0040] In an embodiment of the present invention, the wire is located in the wire groove. One end of the wire is connected to the corresponding graphite carbon ring through a wire passing hole, and the other end of the wire passes upward through the wire groove and is connected to the electrode of a DC regulated power supply. The connection between the wire passing hole and the wire is sealed with glass glue.

[0041] The wire of the grouting pipe with a greater depth is longer, and is connected to the DC regulated power supply through the wire grooves in all the upper grouting pipes of this section. For example, the wire of the bottommost grouting pipe first passes through the wire groove of the bottommost grouting pipe and then sequentially through the wire grooves of the upper grouting pipes, and finally is connected to the power supply.

[0042] In an embodiment of the present invention, the inner diameter of the graphite carbon ring is larger than the outer diameter of the grouting pipe. Rubber rings 13 are filled between the upper and lower ports of the graphite carbon ring and the outer peripheral part of the grouting pipe, and are sealed with glass glue.

[0043] After connecting the graphite carbon ring and the wire through the wire passing hole, move the graphite carbon ring to the corresponding position outside the grouting pipe, fill the gaps at the upper and lower connection ports of the grouting pipe and the graphite carbon ring with rubber rings, and reinforce the connection ports with glass glue.

[0044] Considering that the injected cementing liquid contains CaCl2 solution, electroosmotic treatment after a large amount of injection may cause corrosion at the connection between the wire and the carbon ring. To ensure the normal use of the equipment, the connection between the wire and the carbon ring needs to be secondarily reinforced and wrapped with glass glue.

[0045] In an embodiment of the present invention, a conical plugging head 14 with a tip facing downward is screwed onto the bottommost end of the bottommost grouting pipe of the electroosmotic grouting pipe.

[0046] In an embodiment of the present invention, a pumping and grouting device 15 is provided inside the electroosmotic grouting pipe.

[0047] In the embodiment of the present invention, grouting holes 16 are arranged on the periphery of the grouting and pumping device. The grouting holes communicate with the inner cavity of the grouting and pumping device. The top of the inner cavity communicates with a conduit 17. The top of the conduit is connected to a hose through a pneumatic joint, and the hose is connected to an external grouting device or a slurry pumping device; sealing rings 18 are fixedly arranged on the outer periphery of the grouting and pumping device above and below the grouting holes to axially move in contact with the inner peripheral wall of the grouting pipe and play a sealing role.

[0048] During grouting, the grouting and pumping device can axially move in the electroosmotic grouting pipe, so as to achieve layered grouting.

[0049] In the embodiment of the present invention, since electroosmotic treatment is required during the reinforcement process, in order to avoid corrosion of the electroosmotic grouting pipe structure, both the grouting pipe and the grouting and pumping device are made of high-pressure-resistant PVC materials. At the same time, the outer surface of the grouting pipe is wrapped with geotextile to play a filtering role, which can not only prevent sand particles from entering the inside of the electroosmotic grouting pipe, but also allow the slurry to flow smoothly into the sand to be reinforced or pump out the slurry in the soil body.

[0050] In the embodiment of the present invention, the reinforcement method of the electroosmotic grouting structure for improving the uniform distribution of enzyme-induced mineralization products in shallow sand includes the following steps: Step 1: Level the shallow sand site to be reinforced; Step 2: Drill holes on the sand site to be reinforced, and the number of drill holes ≥ 2; the hole spacing of the electroosmotic grouting pipes that are mutually cathode and anode should not exceed 80 cm; Step 3: Splice the grouting pipes according to the drilling depth and quantity. When splicing the electroosmotic grouting pipes, it is necessary to ensure that the wire grooves of each grouting pipe are aligned with the notches of each sleeve. Select wires of different lengths according to the positions of different carbon rings and place them into the wire grooves. Then lay the groove covers. One end of the wire is connected to the carbon ring through the wire passing hole, and the other end is connected to a DC regulated power supply through the top of the grouting pipe; Step 4: Insert the electroosmotic grouting pipe into the drill hole. After the electroosmotic grouting pipe is lowered to the bottom of the drill hole, connect the grouting and pumping device to an external grouting device or a slurry pumping device through a hose, and then lower the grouting and pumping device to the bottom of the grouting pipe; Step 5: Connect the circuit, and then carry out electroosmotic combined EICP grouting reinforcement treatment; after repeated reinforcement, fill the drill hole with graded sand and gravel to complete the electroosmotic combined EICP grouting reinforcement of a large area of shallow sand.

[0051] Further, the method for electroosmotic combined EICP grouting of the large area of shallow sand to be reinforced in Step 5 is as follows: Select two adjacent electroosmotic grouting pipes (the electroosmotic grouting pipes have the same length), place the grouting and pumping device at the bottom of each electroosmotic grouting pipe respectively, and connect all the wires connected to the carbon rings on the two electroosmotic grouting pipes to the positive and negative electrodes of the DC regulated power supply respectively, that is, the two adjacent electroosmotic grouting pipes are respectively the cathode and the anode.

[0052] Prepare slurry. In order to improve the uniformity of the distribution of calcium carbonate generated by the EICP reaction in the sand, excess anions need to be generated in the cathode grouting pipe and excess cations need to be generated in the anode. For the cathode grouting pipe, the concentrations of urea and calcium chloride in the cementing liquid are 1 mol / L and 0.5 mol / L respectively, and for the anode grouting pipe, the concentrations of urea and calcium chloride in the cementing liquid are 0.5 mol / L and 1 mol / L respectively. The volume ratio of urease solution to cementing liquid in the two pipes is 1:1.

[0053] Grouting and electroosmosis. Connect two electroosmosis grouting pipes to two grouting equipments respectively, apply a certain grouting pressure, and merge the binder and urease solution into the water pipes connected to each pumping grouting device through two different pipelines. Under the action of pressure, the slurry enters the sand layer to be reinforced. After the grouting of one layer of soil is completed, the position of the pumping grouting device in the electroosmosis grouting pipe is raised, and the grouting of another layer of soil is carried out until the grouting of all layered soils is completed. Connect each wire to a DC regulated power supply, and turn on the DC regulated power supply for electroosmosis during the grouting process to make the excess Ca in the soil around the anode grouting pipe 2+ and the excess CO3 generated by urease decomposing urea in the soil around the cathode grouting pipe 2- Further diffuse to the soil in the middle of the two tubes and react to generate mineralized products. Considering that sand is mainly composed of quartz, feldspar, mica, and a small amount of organic matter and clay minerals, the conductivity of the sand itself is very low, so the potential gradient is controlled between 0.25-0.75V / cm, and the electroosmosis time is 4-8h.

[0054] Reversal of grouting and electrodes. After the electroosmosis treatment, let it stand for 12 hours. After the EICP slurry has basically reacted, connect the grouting devices in the two electroosmosis grouting pipes to two grouting devices to extract grout from the reinforced sand layer. Furthermore, reverse the electrode properties of the grouting pipes, connect the grouting pipe originally connected to the negative pole of the power supply to the positive pole of the power supply, and connect the grouting pipe originally connected to the positive pole of the power supply to the negative pole of the power supply. That is, the original cathode grouting pipe becomes the anode grouting pipe, and the anode grouting pipe is the opposite.

[0055] Repeat slurry preparation, grouting, electroosmosis and grouting. Furthermore, for large areas of shallow sandy soil to be reinforced, repeated electroosmosis combined with EICP grouting and repeated grouting can be carried out to ensure the reinforcement effect.

[0056] The external grouting equipment can be a pressure grouting pump or a peristaltic pump, and the grouting equipment can be a vacuum pump. During grouting, two grouting equipment are connected to the conduits of the grouting pumps inside the two electroosmotic grouting pipes through hoses, and the other end of the grouting pump is connected to the urease solution and the cementing liquid; during grouting, the two grouting pumps are connected to the two grouting equipments respectively.

[0057] During the stratified grouting process, turn on the DC regulated power supply for electroosmosis to make the excessive Ca in the soil around the anode grouting pipe 2+ and the excessive CO3 produced by the decomposition of urea in the soil around the cathode grouting pipe 2- further diffuse into the soil between the two pipes and react to form mineralization products. Considering that sand particles are almost non-conductive, when strengthening shallow sandy soil layers, the electroosmotic gradient should not be too high and should be between 0.25 - 0.75 V / cm, and the electroosmosis time should be controlled within 4 - 8 h. After electroosmosis is completed, let it stand for 12 h and then pump out the waste liquid.

[0058] After each slurry pumping, reverse the electrode properties of the electroosmotic grouting pipe, connect the grouting pipe originally connected to the negative pole of the power supply to the positive pole of the power supply, and connect the grouting pipe originally connected to the positive pole of the power supply to the negative pole of the power supply. That is, the original cathode grouting pipe becomes the anode grouting pipe, and vice versa for the anode grouting pipe. Repeat the slurry preparation, grouting, electroosmosis, and slurry pumping operations. Further, for large-area shallow sandy soil to be strengthened, repeated electroosmosis combined with EICP grouting and repeated slurry pumping can be carried out to ensure the strengthening effect.

[0059] While having the functions of grouting and slurry pumping, the grouting pipe also has the characteristics of electroosmotic strengthening. By using the method of combined grouting and electroosmosis, it effectively improves the diffusion distance of Ca 2+ and CO3 2- in the soil, thereby improving the uniformity of the distribution of mineralization products in the soil and accurately controlling the strengthening range. After the grouting strengthening work is completed, the waste liquid can be recycled to prevent environmental pollution.

[0060] The above is only a preferred embodiment of the present invention and is not a limitation to the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. An electroosmotic grouting structure for improving the uniform distribution of enzyme-induced mineralization products in shallow sand, characterized in that: It includes a first electroosmosis grouting component and a second electroosmosis grouting component inserted into the shallow sand to be reinforced, the first electroosmosis grouting component is connected to the positive pole of the DC stabilized power supply via a wire, and the second electroosmosis grouting component is connected to the negative pole of the DC stabilized power supply via a wire. The first and second electroosmosis grouting components each include at least one electroosmosis grouting pipe, and the outer periphery of the electroosmosis grouting pipe is provided with a graphite carbon ring.

2. The electroosmosis grouting structure for improving uniform distribution of enzyme-induced mineralization products in shallow sand according to claim 1, characterized in that: The electroosmosis grouting pipes are composed of at least one grouting pipe, and a plurality of grouting holes are arranged axially on the periphery of the grouting pipe, and a wire groove parallel to the axial direction is arranged on the outer periphery of the grouting pipe, a groove cover is arranged on the groove opening of the wire groove, and a threading hole is arranged on the groove cover.

3. The electroosmosis grouting structure for improving uniform distribution of enzyme-induced mineralization products in shallow sand according to claim 2, characterized in that: The number of the graphite carbon rings on each grouting pipe is two, and the number of the threading holes on each grouting pipe is also two.

4. The electroosmosis grouting structure for improving uniform distribution of enzyme-induced mineralization products in shallow sand according to claim 2, characterized in that: Both ends of the grouting pipe are provided with external threaded connection sections, and the external threaded connection sections of two coaxially adjacent grouting pipes are connected as a whole through a casing. An internal thread is provided on the inner circumferential wall of the casing for respectively threading with the external threaded connection sections of the two coaxially adjacent grouting pipes, and a notch parallel to the axial direction is provided on the circumference of the casing, so that the casing as a whole is in a "C" shape.

5. The electroosmosis grouting structure for improving uniform distribution of enzyme-induced mineralization products in shallow sand according to claim 4, characterized in that: The notch is aligned with the wire groove, which facilitates the laying of the wires.

6. The electroosmosis grouting structure for improving uniform distribution of enzyme-induced mineralization products in shallow sand according to claim 3, characterized in that: The wire is located in the wire groove, one end of the wire is connected to the corresponding graphite carbon ring through the wire hole, and the other end of the wire passes upward through the wire groove and is connected to the electrode of the DC voltage-stabilized power supply. The connection between the wire hole and the wire is sealed with glass glue.

7. The electroosmosis grouting structure for improving uniform distribution of enzyme-induced mineralization products in shallow sand according to claim 1, characterized in that: The inner diameter of the graphite carbon ring is larger than the outer diameter of the grouting pipe. The upper and lower ports of the graphite carbon ring and the outer periphery of the grouting pipe are filled with rubber rings and sealed with glass glue.

8. The electroosmosis grouting structure for improving uniform distribution of enzyme-induced mineralization products in shallow sand according to claim 1, characterized in that: The bottom end of the bottom grouting pipe of the electroosmosis grouting pipe is threadedly connected with a conical plugging head with the tip facing downward.

9. The electroosmosis grouting structure for improving uniform distribution of enzyme-induced mineralization products in shallow sand according to claim 1, characterized in that: A grouting device is arranged inside the electroosmosis grouting pipe.

10. The electroosmosis grouting structure for improving uniform distribution of enzyme-induced mineralization products in shallow sand according to claim 9, characterized in that: The grouting device is provided with grouting holes on its periphery, the grouting holes are connected to the inner cavity of the grouting device, the top of the inner cavity is connected to a conduit, the top of the conduit is connected to a hose via a pneumatic joint, and the hose is connected to an external grouting device or a grouting device; the outer periphery of the grouting device is provided with sealing rings above and below the grouting holes for contacting the inner circumferential wall of the grouting pipe for axial movement and sealing.

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