Foaming agent for shield tunneling machine and preparation method thereof

Abstract

The invention provides a foaming agent for a shield tunneling machine and a preparation method of the foaming agent, and relates to the field of foaming agents. The cleaning agent is prepared from the following components in parts by weight: 80 to 100 parts of water, 15 to 30 parts of fatty alcohol polyoxyethylene ether sodium sulfate, 15 to 30 parts of C8-C12 glucose alkyl sugar, 10 to 15 parts of lauryl sodium sulfate, 10 to 15 parts of cocamidopropyl betaine, 10 to 15 parts of citric acid, 5 to 10 parts of esterified starch, 1 to 5 parts of bentonite and 10 to 15 parts of polylactic acid microspheres. The half-life period of the foam can reach 60-70 min, and the volume attenuation rate of the foam is 1t at the shearing rate of 2000 rpm; and wide temperature range adaptability (-10 DEG C to 50 DEG C) is realized.

Description

Technical Field

[0001] This invention relates to the field of foaming agents, and more specifically, to a foaming agent for tunnel boring machines and its preparation method. Background Technology

[0002] As a key auxiliary material for earth pressure balance shield tunneling, shield foam agent has the core functions of improving the performance of excavated soil through micro-bubbles (30-400μm in diameter); extending the service life of mechanical equipment as a lubricating medium; and suppressing dust and noise, etc.

[0003] Typical foaming agent formulations include anionic / nonionic surfactants, foam stabilizers, penetrants, and reinforcing agents. These are mixed with water using a compressed air foaming system and then injected into the soil chamber. Traditional foaming agents often use petroleum-based surfactants, which have a degradation cycle of 5-10 years. Actual measurements on Beijing Metro Line 16 showed that the residual concentration of a certain imported product in the soil after construction reached 12.7 mg / kg, far exceeding the Class II limit of the "Soil Environmental Quality Standard." There is also a risk of heavy metal pollution; some products contain lead, arsenic, and other heavy metals; approximately 35% of products use fluorocarbon surfactants, polluting the environment. Furthermore, some foaming agents, when used in complex strata (such as soft topsoil and hard bottoms), cannot simultaneously meet the needs of sand layer waterproofing and clay lubrication. They also have a narrow applicable temperature range (5-40℃), and in extremely cold regions (below -15℃), the foam half-life is shortened to less than 5 minutes, affecting the continuity of construction.

[0004] In summary, while shield tunneling foam agents are relatively mature, their environmental friendliness and adaptability still need improvement. Summary of the Invention

[0005] The purpose of this invention is to provide a foaming agent for tunnel boring machines, which uses bio-based surfactants as the main raw material, has good biodegradability, is environmentally friendly, and produces foam with a high foaming ratio, a long foam half-life, and does not corrode the equipment.

[0006] Another objective of this invention is to provide a method for preparing foaming agent for tunnel boring machines, which involves mixing the raw materials in steps, and the preparation method is simple and efficient.

[0007] The technical problem solved by this invention is achieved by the following technical solution.

[0008] On one hand, embodiments of the present invention provide a foaming agent for tunnel boring machines, comprising the following raw materials by weight:

[0009] 80-100 parts water, 15-30 parts sodium fatty alcohol polyoxyethylene ether sulfate, 15-30 parts C8-C12 glucosyl sugar, 10-15 parts sodium dodecyl sulfate, 10-15 parts cocamidopropyl betaine, 10-15 parts citric acid, 5-10 parts esterified starch, 5-10 parts bentonite, and 10-15 parts polylactic acid microspheres.

[0010] In some embodiments of the present invention, the raw materials include the following by weight: 80 parts water, 20 parts sodium fatty alcohol polyoxyethylene ether sulfate, 20 parts C8-C12 glucosyl sugar, 15 parts sodium dodecyl sulfate, 10 parts cocamidopropyl betaine, 10 parts citric acid, 5 parts esterified starch, 5 parts bentonite, and 15 parts polylactic acid microspheres.

[0011] In some embodiments of the present invention, the raw materials include the following by weight: 80 parts water, 30 parts sodium fatty alcohol polyoxyethylene ether sulfate, 15 parts C8-C12 glucosyl sugar, 10 parts sodium dodecyl sulfate, 10 parts cocamidopropyl betaine, 10 parts citric acid, 5 parts esterified starch, 5 parts bentonite, and 15 parts polylactic acid microspheres.

[0012] Preferably, the mass ratio of bentonite to esterified starch is 1:1 or 1:2.

[0013] In some embodiments of the present invention, the polylactic acid microspheres are prepared by the following method:

[0014] Polyvinyl alcohol was added to distilled water and stirred at a constant temperature until completely dissolved. After cooling, Tween 80 was added, stirred until dissolved, and filtered to obtain the aqueous phase.

[0015] Polylactic acid was dissolved in dichloromethane and stirred until completely dissolved. Stearic acid was then added and the mixture was ultrasonically dispersed to obtain the oil phase.

[0016] Under water bath heating, the oil phase is dropped into the aqueous phase and stirred continuously until it solidifies into microspheres; the microspheres are separated by centrifugation, washed, and freeze-dried to obtain the polylactic acid microspheres.

[0017] In some embodiments of the present invention, the mass-volume concentration of polyethanol in the aqueous phase is 0.5-2%; the mass-volume concentration of polylactic acid in the oil phase is 2.5-10%; the volume ratio of the oil phase to the aqueous phase is 5:1-10:1; and the amount of stearic acid used is 10-50% of the mass of polylactic acid.

[0018] In some embodiments of the present invention, the esterified starch is prepared by the following method:

[0019] Tapioca starch was added to Na2CO3 buffer solution to prepare a starch emulsion; the temperature was raised to 60-70℃, and vinyl acetate was added dropwise to the starch emulsion while stirring until completely dissolved; the reaction was kept at this temperature for 3-5 hours; then dilute hydrochloric acid was added to adjust the pH of the system to 6-7, the mixture was filtered, washed, and the filter cake was dried in an oven at 50-60℃, pulverized, and passed through an 80-100 mesh sieve to obtain the esterified starch.

[0020] In some embodiments of the present invention, the mass ratio of the cassava starch to the vinyl acetate is 1:0.5-1.

[0021] On the other hand, embodiments of the present invention provide a method for preparing a foaming agent for a tunnel boring machine, comprising the following steps:

[0022] S1, sodium fatty alcohol polyoxyethylene ether sulfate, C8-C12 glucose alkyl sugar and some water are mixed at low speed to obtain mixture A;

[0023] S2, sodium dodecyl sulfate, cocamidopropyl betaine and some water are mixed at low speed to obtain mixture B;

[0024] S3, citric acid, esterified starch, bentonite, polylactic acid microspheres and some water are mixed to obtain mixture C;

[0025] S4. Mix mixture A, mixture B, mixture C and the remaining water to obtain the foaming agent.

[0026] In some embodiments of the present invention, the volume ratio of the water volume in step S1, the water volume in step S2, the water volume in step S3, and the water volume in step S4 is 1:1:1:2.

[0027] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0028] The foaming agent provided by this invention has a foam half-life of 60-70 minutes, a foam volume decay rate of <15% at a shear rate of 2000 rpm, and wide temperature range adaptability (-10℃-50℃). Polylactic acid microspheres are added to the foaming agent of this invention, which have a slow-release effect and act as a surfactant carrier. Upon rupture, the polylactic acid microspheres release stearic acid, enhancing the lubricity of the foaming agent and extending the service life of tunnel boring machine (TBM) tools. Esterified starch and bentonite form a three-dimensional network structure, which can improve the shear strength of the foam and reduce the foam decay rate. The combination of C8-C12 glucosyl glycoside and cocamidopropyl betaine allows for foaming at low temperatures, with a foaming ratio still exceeding 12 times at 0℃, making it suitable for TBM construction in cold regions. Citric acid chelates Ca in water. 2+ and Mg 2+It can inhibit the damage of foam caused by hard water ions; at the same time, it synergistically adsorbs organic matter volatilized at high temperatures with bentonite, and the foam stability retention rate is >80% at 50℃. Bentonite (5-8 parts) and citric acid (10-15 parts) work synergistically to adsorb fine particles <0.075mm in the formation (adsorption rate >90%), reducing the mud cake thickness from 10mm to 3mm in clay formations and reducing the frequency of mud cleaning.

[0029] The foaming agent provided by this invention reduces the internal friction angle of the slag from 38° to 22° after foam injection, decreasing the cutting resistance of the cutterhead by 30%. Simultaneously, the foam lubrication effect reduces the friction coefficient between the cutterhead and the soil from 0.4 to 0.25, resulting in a significant decrease in torque. In gravel strata (particle size 5-20mm), when the foam injection ratio (foam volume / discharge volume) is 50%, the discharge velocity reaches 8-10m / sqm. 3 / h, increasing daily tunneling progress by 15-20%.

[0030] Secondly, the foaming agent provided by this invention contains biodegradable materials in its raw materials, including glucosyl glycoside (APG, 98% degradation rate in 28 days), esterified starch (DS=0.3, 95% degradation rate in 28 days), and polylactic acid microspheres (PLA, 92% degradation rate in 180 days). These materials are environmentally friendly and will not pollute groundwater. Furthermore, the chelating effect of citric acid reduces heavy metal ions. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0032] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to specific embodiments.

[0033] On one hand, embodiments of the present invention provide a foaming agent for tunnel boring machines, comprising the following raw materials by weight:

[0034] 80-100 parts water, 15-30 parts sodium fatty alcohol polyoxyethylene ether sulfate, 15-30 parts C8-C12 glucosyl sugar, 10-15 parts sodium dodecyl sulfate, 10-15 parts cocamidopropyl betaine, 10-15 parts citric acid, 5-10 parts esterified starch, 5-10 parts bentonite, and 10-15 parts polylactic acid microspheres.

[0035] In some embodiments of the present invention, the raw materials include the following by weight: 80 parts water, 20 parts sodium fatty alcohol polyoxyethylene ether sulfate, 20 parts C8-C12 glucosyl sugar, 15 parts sodium dodecyl sulfate, 10 parts cocamidopropyl betaine, 10 parts citric acid, 5 parts esterified starch, 5 parts bentonite, and 15 parts polylactic acid microspheres.

[0036] In some embodiments of the present invention, the raw materials include the following by weight: 80 parts water, 30 parts sodium fatty alcohol polyoxyethylene ether sulfate, 15 parts C8-C12 glucosyl sugar, 10 parts sodium dodecyl sulfate, 10 parts cocamidopropyl betaine, 10 parts citric acid, 5 parts esterified starch, 5 parts bentonite, and 15 parts polylactic acid microspheres.

[0037] Preferably, the mass ratio of bentonite to esterified starch is 1:1 or 1:2.

[0038] In some embodiments of the present invention, the polylactic acid microspheres are prepared by the following method:

[0039] Polyvinyl alcohol was added to distilled water and stirred at a constant temperature of 75°C until completely dissolved. After cooling, Tween 80 was added, stirred until dissolved, and filtered to obtain an aqueous phase. The mass-volume concentration of polyvinyl alcohol was 0.5-2%.

[0040] Dissolve polylactic acid in dichloromethane and stir until completely dissolved. Then add stearic acid, the amount of which is 10-50% of the mass of polylactic acid. Disperse the mixture evenly by ultrasonication to obtain an oil phase. The mass-volume concentration of polylactic acid in this oil phase is 2.5-10%.

[0041] Under water bath heating, the oil phase is dropped into the aqueous phase at a volume ratio of 5:1 to 10:1, and the mixture is continuously stirred until it solidifies into microspheres; the microspheres are separated by centrifugation, washed, and freeze-dried to obtain the polylactic acid microspheres.

[0042] In some embodiments of the present invention, the esterified starch is prepared by the following method:

[0043] 100g of cassava starch was added to 400mL of Na2CO3 buffer (pH=6-7) to prepare a 20% starch emulsion; the temperature was raised to 60-70℃, and vinyl acetate (50-100g) was added dropwise to the starch emulsion while stirring until completely dissolved; the reaction was kept at this temperature for 3-5 hours; then dilute hydrochloric acid was added to adjust the pH of the system to 6-7, the mixture was filtered, washed, and the filter cake was dried in an oven at 50-60℃. After pulverizing, the cake was passed through an 80-100 mesh sieve to obtain the esterified starch.

[0044] On the other hand, embodiments of the present invention provide a method for preparing a foaming agent for a tunnel boring machine, comprising the following steps:

[0045] S1, sodium fatty alcohol polyoxyethylene ether sulfate, C8-C12 glucose alkyl sugar and 20% water are mixed at low speed to obtain mixture A;

[0046] S2, sodium dodecyl sulfate, cocamidopropyl betaine and 20% water are mixed at low speed to obtain mixture B;

[0047] S3, citric acid, esterified starch, bentonite, polylactic acid microspheres and 20% water are mixed to obtain mixture C;

[0048] S4. Mix mixture A, mixture B, mixture C and 40% water to obtain the foaming agent.

[0049] When using this foaming agent, mix it with water at a volume ratio of 1:40 and then introduce it into a foam generator. Under the action of an air compressor, foam is produced.

[0050] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0051] Example 1

[0052] The foaming agent of this embodiment is prepared according to the following proportions:

[0053] 80 parts water, 20 parts sodium fatty alcohol polyoxyethylene ether sulfate, 20 parts C8-C12 glucosyl sugar (decyl glucoside), 15 parts sodium dodecyl sulfate, 10 parts cocamidopropyl betaine, 10 parts citric acid, 5 parts esterified starch, 5 parts bentonite, and 15 parts polylactic acid microspheres.

[0054] The polylactic acid microspheres were prepared by the following method:

[0055] Polyvinyl alcohol was added to distilled water and stirred at a constant temperature of 75°C until completely dissolved. After cooling, Tween 80 was added, stirred until dissolved, and filtered to obtain an aqueous phase. The mass-volume concentration of polyvinyl alcohol was 0.5-2%.

[0056] Dissolve polylactic acid in dichloromethane and stir until completely dissolved. Then add stearic acid, the amount of which is 10-50% of the mass of polylactic acid. Disperse the mixture evenly by ultrasonication to obtain an oil phase. The mass-volume concentration of polylactic acid in this oil phase is 2.5-10%.

[0057] Under water bath heating, the oil phase is dropped into the aqueous phase at a volume ratio of 5:1 to 10:1, and the mixture is continuously stirred until it solidifies into microspheres; the microspheres are separated by centrifugation, washed, and freeze-dried to obtain the polylactic acid microspheres.

[0058] Esterified starch is prepared by the following method:

[0059] 100g of cassava starch was added to 400mL of Na2CO3 buffer (pH=6-7) to prepare a 20% starch emulsion; the temperature was raised to 60-70℃, and 100g of vinyl acetate was added dropwise to the starch emulsion while stirring until completely dissolved; the reaction was kept at this temperature for 3-5 hours; then dilute hydrochloric acid was added to adjust the pH of the system to 6-7, the mixture was filtered, washed, and the filter cake was dried in an oven at 50-60℃. After pulverizing, the cake was passed through an 80-100 mesh sieve to obtain the esterified starch.

[0060] The preparation method of the foaming agent is as follows:

[0061] S1, sodium fatty alcohol polyoxyethylene ether sulfate, C8-C12 glucose alkyl sugar and 20% water are mixed at low speed to obtain mixture A;

[0062] S2, sodium dodecyl sulfate, cocamidopropyl betaine and 20% water are mixed at low speed to obtain mixture B;

[0063] S3, citric acid, esterified starch, bentonite, polylactic acid microspheres and 20% water are mixed to obtain mixture C;

[0064] S4. Mix mixture A, mixture B, mixture C and 40% water to obtain the foaming agent.

[0065] Example 2

[0066] The foaming agent of this embodiment is prepared according to the following proportions:

[0067] 80 parts water, 30 parts sodium fatty alcohol polyoxyethylene ether sulfate, 15 parts C8-C12 glucosyl sugar (decyl glucoside), 10 parts sodium dodecyl sulfate, 10 parts cocamidopropyl betaine, 10 parts citric acid, 5 parts esterified starch, 5 parts bentonite, and 15 parts polylactic acid microspheres.

[0068] The preparation methods of all raw materials and foaming agents are the same as those in Example 1.

[0069] Example 3

[0070] The foaming agent of this embodiment is prepared according to the following proportions:

[0071] 100 parts water, 30 parts sodium fatty alcohol polyoxyethylene ether sulfate, 30 parts C8-C12 glucosyl sugar (decyl glucoside), 10 parts sodium dodecyl sulfate, 15 parts cocamidopropyl betaine, 10 parts citric acid, 10 parts esterified starch, 1 part bentonite, and 15 parts polylactic acid microspheres.

[0072] The preparation methods of all raw materials and foaming agents are the same as those in Example 1.

[0073] Example 4

[0074] The foaming agent of this embodiment is prepared according to the following proportions:

[0075] 100 parts water, 20 parts sodium fatty alcohol polyoxyethylene ether sulfate, 30 parts C8-C12 glucosyl sugar (decyl glucoside), 15 parts sodium dodecyl sulfate, 15 parts cocamidopropyl betaine, 15 parts citric acid, 10 parts esterified starch, 5 parts bentonite, and 10 parts polylactic acid microspheres.

[0076] The preparation methods of all raw materials and foaming agents are the same as those in Example 1.

[0077] Example 5

[0078] The foaming agent of this embodiment is prepared according to the following proportions:

[0079] 100 parts water, 15 parts sodium fatty alcohol polyoxyethylene ether sulfate, 30 parts C8-C12 glucosyl sugar (decyl glucoside), 15 parts sodium dodecyl sulfate, 10 parts cocamidopropyl betaine, 10 parts citric acid, 10 parts esterified starch, 5 parts bentonite, and 10 parts polylactic acid microspheres.

[0080] The preparation methods of all raw materials and foaming agents are the same as those in Example 1.

[0081] Comparative Example 1

[0082] The difference from Example 1 is that polylactic acid microspheres are not added in this comparative example; water is used instead. The remaining raw material ratios and preparation methods are the same as in Example 1.

[0083] Comparative Example 2

[0084] The difference from Example 1 is that, in this comparative example, esterified starch is not added, and water is used instead. The remaining raw material ratios and preparation methods are the same as in Example 1.

[0085] Comparative Example 3

[0086] The difference from Example 1 is that, in this comparative example, esterified starch and polylactic acid microspheres are not added, and water is used instead. The remaining raw material ratios and preparation methods are the same as in Example 1.

[0087] Experimental Example

[0088] 1. Mix 2 mL of foaming agent from Examples 1-5 and Comparative Examples 1-3 with 100 mL of water and stir for 1 minute using a high-speed mixer (4000 r / min) to generate uniform foam.

[0089] Immediately pour the generated foam into a graduated cylinder (1000 mL) and record the initial foam volume V1. Let the foam stand and observe the volume of liquid precipitated at the bottom of the graduated cylinder. When the precipitated liquid reaches 50 mL, stop timing and record the time t. 1 / 2 This is the foam half-life. The foaming rate (ER) is calculated using the formula: ER = V1 / V0, where V0 is the volume of the foaming agent. The experimental results are shown in Table 1.

[0090] Test conditions: Laboratory temperature controlled at 20-25℃, relative humidity not less than 50%. The foaming agent solution must be completely dissolved, without stratification or sedimentation. The test water must be clean water, with the water temperature controlled at 10-30℃.

[0091] Table 1

[0092]

[0093]

[0094] As can be seen from Table 1 above, the foaming agent provided in the embodiments of the present invention has a long foam half-life, high foam strength, is not easy to break, has a high foaming ratio, and can produce a large amount of foam.

[0095] In summary, the foaming agent provided in this embodiment of the invention has a foam half-life of 60-70 minutes, a foam volume decay rate of <15% at a shear rate of 2000 rpm, and wide temperature range adaptability (-10℃-50℃). Polylactic acid microspheres are added to the foaming agent of this invention, which have a slow-release effect and act as a surfactant carrier. Upon rupture, the polylactic acid microspheres release stearic acid, enhancing the lubricity of the foaming agent and extending the service life of the tunnel boring machine. The esterified starch and bentonite form a three-dimensional network structure, which improves the shear strength of the foam and reduces the foam decay rate.

[0096] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A foaming agent for tunnel boring machines, characterized in that, By weight, it includes the following ingredients: 80-100 parts water, 15-30 parts sodium fatty alcohol polyoxyethylene ether sulfate, 15-30 parts C8-C12 glucosyl sugar, 10-15 parts sodium dodecyl sulfate, 10-15 parts cocamidopropyl betaine, 10-15 parts citric acid, 5-10 parts esterified starch, 1-5 parts bentonite, and 10-15 parts polylactic acid microspheres.

2. The foaming agent for tunnel boring machines according to claim 1, characterized in that, By weight, it includes the following raw materials: 80 parts water, 20 parts sodium fatty alcohol polyoxyethylene ether sulfate, 20 parts C8-C12 glucosyl sugar, 15 parts sodium dodecyl sulfate, 10 parts cocamidopropyl betaine, 10 parts citric acid, 5 parts esterified starch, 5 parts bentonite, and 15 parts polylactic acid microspheres.

3. The foaming agent for tunnel boring machines according to claim 1, characterized in that, By weight, it includes the following raw materials: 80 parts water, 30 parts sodium fatty alcohol polyoxyethylene ether sulfate, 15 parts C8-C12 glucosyl sugar, 10 parts sodium dodecyl sulfate, 10 parts cocamidopropyl betaine, 10 parts citric acid, 5 parts esterified starch, 5 parts bentonite, and 15 parts polylactic acid microspheres.

4. The foaming agent for tunnel boring machines according to claim 1, characterized in that, The polylactic acid microspheres were prepared by the following method: Polyvinyl alcohol was added to distilled water and stirred at a constant temperature until completely dissolved. After cooling, Tween 80 was added, stirred until dissolved, and filtered to obtain the aqueous phase. Polylactic acid was dissolved in dichloromethane and stirred until completely dissolved. Stearic acid was then added and the mixture was ultrasonically dispersed to obtain the oil phase. Under water bath heating, the oil phase is dropped into the aqueous phase and stirred continuously until it solidifies into microspheres; the microspheres are separated by centrifugation, washed, and freeze-dried to obtain the polylactic acid microspheres.

5. The foaming agent for tunnel boring machines according to claim 4, characterized in that, In the aqueous phase, the mass-volume concentration of polyethanol is 0.5-2%; in the oil phase, the mass-volume concentration of polylactic acid is 2.5-10%; the volume ratio of the oil phase to the aqueous phase is 5:1-10:1; and the amount of stearic acid used is 10-50% of the mass of polylactic acid.

6. The foaming agent for tunnel boring machines according to claim 1, characterized in that, The esterified starch is prepared by the following method: Tapioca starch was added to Na2CO3 buffer solution to prepare a starch emulsion; the temperature was raised to 60-70℃, and vinyl acetate was added dropwise to the starch emulsion while stirring until completely dissolved; the reaction was kept at this temperature for 3-5 hours; then dilute hydrochloric acid was added to adjust the pH of the system to 6-7, the mixture was filtered, washed, and the filter cake was dried in an oven at 50-60℃, pulverized, and passed through an 80-100 mesh sieve to obtain the esterified starch.

7. The foaming agent for tunnel boring machines according to claim 6, characterized in that, The mass ratio of the cassava starch to the vinyl acetate is 1:0.5-1.

8. A method for preparing a foaming agent for a tunnel boring machine as described in any one of claims 1-7, characterized in that, Includes the following steps: S1, sodium fatty alcohol polyoxyethylene ether sulfate, C8-C12 glucose alkyl sugar and some water are mixed at low speed to obtain mixture A; S2, sodium dodecyl sulfate, cocamidopropyl betaine and some water are mixed at low speed to obtain mixture B; S3, citric acid, esterified starch, bentonite, polylactic acid microspheres and some water are mixed to obtain mixture C; S4. Mix mixture A, mixture B, mixture C and the remaining water to obtain the foaming agent.

9. The method for preparing the foaming agent for tunnel boring machines according to claim 6, characterized in that, The volume ratio of the water used in step S1, step S2, step S3, and step S4 is 1:1:1:2.

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