A CMC transparent slurry, its preparation method and its application

Abstract

The present invention relates to the technical field of mud materials, in particular to a CMC transparent slurry, its preparation method and its application. The following solution is now proposed. The preparation method includes first mixing water, calcium-based bentonite and Na2CO3, and then adding NaOH and mixing to obtain a first mixed solution; adding MgCl2 to the first mixed solution, mixing and standing to obtain a second mixed solution; heating the second mixed solution to 78°C - 79°C, then adding a mixed solution of MMA and BPO and stirring to obtain a third mixed solution; adding a dispersant to the third mixed solution and cooling to 74 - 75°C, stirring until the solution becomes transparent, stopping heating, and standing to obtain a fourth mixed solution; adding a weighting agent and CMC to the fourth mixed solution and stirring and mixing to obtain a CMC transparent slurry. The slurry prepared by the present invention has high transparency, solving the problem that due to the turbid state of the bentonite mud used in construction, the movement state of the slag stones in the pipeline of the circulation system cannot be directly observed.

Description

Technical Field

[0001] The present invention relates to the field of mud materials, and in particular to a CMC transparent slurry, a preparation method thereof, and an application thereof. Background Art

[0002] The slurry shield is widely used in the construction of highway tunnels and subway tunnels due to the safety and efficiency of its construction, especially in cross-river projects and water conveyance projects. During the tunneling process of the slurry shield, fresh bentonite slurry is pumped into the excavation chamber (mud chamber) through the slurry inlet pipeline in the circulation system to balance the water and soil pressure in front of the face. There are large-sized irregular rock slag particles cut from the excavation surface in the slurry discharge pipeline of the slurry shield circulation system, resulting in local turbulence in the pipeline and a relatively complex movement. Therefore, it is of great significance to analyze the migration characteristics of large-sized slag stones in the pipeline. However, due to the turbid and opaque bentonite slurry used in construction, it is impossible to directly observe the movement state of the slag stones in the pipeline of the circulation system, which brings difficulties to exploring the migration characteristics of the slag stones in the circulation system. For this reason, the present invention proposes a CMC transparent slurry, a preparation method thereof, and an application thereof. Summary of the Invention

[0003] To solve the problems in the prior art, the present invention proposes a CMC transparent slurry, a preparation method thereof, and an application thereof.

[0004] In order to make the slurry have a high transparency, it is necessary to reduce the addition amount of bentonite. However, reducing the addition amount of bentonite will cause the corresponding performance of the bentonite slurry to decrease. Therefore, it is necessary to modify the bentonite so that it still has its original performance while having a high transparency. The present invention reduces the usage amount of calcium-based bentonite, constructs a salt-containing system in the calcium-based bentonite slurry first, and then performs alkali modification on the calcium-based bentonite slurry to improve the dispersion between bentonite particles in the slurry to enhance the light transmittance and increase the viscosity of the slurry. Finally, PMMA (polymethyl methacrylate) polymer modification is performed on the alkali-modified slurry. There are branched chains of PMMA molecules in the modified slurry, making the prepared slurry have high transparency and good lubricating performance, which is beneficial to the transportation of large-sized irregular rock slag particles cut from the excavation surface in the slurry discharge pipeline of the slurry shield circulation system. The prepared slurry increases the strength of the slurry after forming the mud cake and has high anti-permeability performance.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A CMC transparent slurry, a preparation method thereof, and an application thereof, comprising the following steps:

[0007] Step 1: First, mix water, calcium-based bentonite, and Na2CO3, and then add NaOH and mix well to obtain a first mixed solution;

[0008] Step 2: Add MgCl2 to the first mixed solution, mix well and let stand to obtain a second mixed solution;

[0009] Step 3: Heat the second mixed solution to 78°C - 79°C, then add a mixed solution of MMA and BPO and stir to obtain a third mixed solution;

[0010] Step 4: Add a dispersant to the third mixed solution and cool it to 74 - 75°C, stir until the solution becomes transparent, stop heating, and let stand to obtain a fourth mixed solution;

[0011] Step 5: Add a weighting agent and CMC to the fourth mixed solution, mix well to obtain a CMC transparent slurry.

[0012] In some embodiments, the preparation method further includes curing the obtained CMC transparent slurry, and the curing method includes: every 2 - 3h, stir evenly at 500 - 600rpm for 5min, and the curing time is 20 - 24h.

[0013] In some embodiments, the CMC is sodium carboxymethyl cellulose powder with a molecular weight of 250000g / mol, the weighting agent includes barite and perlite, and the dispersant includes lignosulfonate and composite phosphate.

[0014] In some embodiments, the weight ratio of each component is: water: calcium-based bentonite: Na2CO3: NaOH: MgCl2: MMA: BPO: dispersant: weighting agent: CMC = 100: 4 - 5: 0.3 - 0.5: 0.3 - 0.5: 0.2 - 0.3: 4.5 - 6: 0.08 - 0.12: 0.5 - 0.8: 0.7 - 1: 2.5 - 3.5.

[0015] In some embodiments, the standing time in Step 2 is 18 - 25min.

[0016] In some embodiments, the mixed solution of MMA and BPO in Step 3 is added to the second mixed solution in three equal portions, stirring while adding, and the time interval between each addition is 4 - 5min, and stir evenly at 1000 - 1300rpm for 0.5 - 0.8h.

[0017] In some embodiments, in Step 4, stir evenly at 700 - 900rpm for 0.3 - 0.5h until the solution becomes transparent, and the standing time is 1.5 - 2h.

[0018] In some embodiments, the weight ratios of the components are as follows: water: calcium-based bentonite: Na2CO3: NaOH: MgCl2: MMA: BPO: dispersant: weighting agent: CMC = 100: 4: 0.4: 0.4: 0.3: 5: 0.09: 0.7: 0.8: 3.

[0019] The CMC transparent slurry prepared by the above preparation method.

[0020] The application of the above CMC transparent slurry in slurry shield construction or for replacing bentonite mud in the slurry shield circulation system.

[0021] Advantages of the present invention:

[0022] 1. The permeability coefficient of the solidified mud skin prepared from the CMC transparent slurry prepared by the method proposed by the present invention is in the range of 1.40 - 1.5x10 -5 cm / s, with low water permeability, that is, good anti-permeability performance, which can prevent water in the soil trough wall from penetrating into the tunnel during shield tunneling;

[0023] 2. The viscosity of the CMC transparent slurry prepared by the method proposed by the present invention is between 17 and 20.3 Pa·s. The slurry has a high viscosity, and in addition, the slurry contains polymethyl methacrylate, making the mud skin formed by the slurry have high strength. During shield tunneling, a mud skin with very low water permeability will be formed on the soil trough wall, so that the hydrostatic pressure of the slurry can effectively act on the trough wall, preventing the trough wall from peeling off and playing a role in strengthening the trough wall;

[0024] 3. The transparency of the CMC transparent slurry prepared by the method proposed by the present invention is between 308 - 315 mm, with high transparency, solving the problem that it is impossible to directly observe the movement state of slag stones in the circulation system pipeline due to the turbid and opaque bentonite mud used in construction. Description of the drawings

[0025] Figure 1 It is a broken line graph of the permeability coefficients of Examples 1 - 6 and Comparative Example 1 of the present invention;

[0026] Figure 2 It is a scanning electron microscope SEM image of the transparent slurry prepared in the manner of Comparative Example 1;

[0027] Figure 3 It is a scanning electron microscope SEM image of the transparent slurry prepared in the manner of Example 1 of the method of the present invention. Detailed implementation manners

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0029] In the present invention, MMA refers to methyl methacrylate, and BPO refers to benzoyl peroxide.

[0030] Example 1

[0031] Prepare raw materials according to water: calcium-based bentonite: Na2CO3: NaOH: MgCl2: MMA: BPO: dispersant: weighting agent: CMC = 100:4:0.3:0.3:0.2:4.5:0.08:0.5:0.7:2.5 (the raw material values are the left endpoint values of the range values), and take the left endpoint values of the corresponding range values for the magnetic stirrer rotation speed, reaction temperature, curing time, standing time, and the batch addition time of the mixed solution of MMA and BPO, etc.

[0032] Step 1: At room temperature, add 1000 g of water, 40 g of calcium-based bentonite, and 3 g of Na2CO3 into a container made of pp material, and stir with a magnetic stirrer at a rotation speed of 500 rpm to mix the water, calcium-based bentonite, and Na2CO3 evenly. Then add 3 g of NaOH into the container and mix well to obtain the first mixed solution.

[0033] Step 2: Keep the stirring rate of the magnetic stirrer unchanged, add 2 g of MgCl2 into the first mixed solution, mix well and let it stand for 18 min to obtain the second mixed solution.

[0034] Step 3: Mix 45 g of MMA and 0.8 g of BPO to obtain a mixed solution of MMA and BPO. Heat the second mixed solution to 78 °C, and then add the mixed solution of MMA and BPO into the second mixed solution in three equal weight portions, stirring while adding, with an interval of 4 min for each addition. Adjust the rotation speed of the magnetic stirrer to 1000 rpm and stir evenly for 0.5 h to obtain the third mixed solution.

[0035] Step 4: Adjust the rotation speed of the magnetic stirrer to 700 rpm, add 5 g of lignosulfonate (dispersant) into the third mixed solution, and cool down to 74 °C. Stir for 0.3 h until the solution becomes transparent, stop heating, and let it stand for 1.5 h to obtain the fourth mixed solution.

[0036] Step 5: Keep the stirring rate of the magnetic stirrer unchanged, add 7 g of barite (weighting agent) and 25 g of sodium carboxymethylcellulose powder (CMC) with a molecular weight of 250000 g / mol into the fourth mixed solution, and stir well to obtain the CMC transparent slurry.

[0037] Step 6: Cure the prepared CMC transparent slurry: Stir at a constant speed of 500 rpm for 5 min every 2 h, and the curing time is 20 h.

[0038] Example 2

[0039] Prepare raw materials according to water: calcium-based bentonite: Na2CO3: NaOH: MgCl2: MMA: BPO: dispersant: weighting agent: CMC = 100: 4: 0.3: 0.3: 0.2: 4.5: 0.08: 0.5: 0.7: 2.5 (the content of each component of the raw material remains unchanged, and the raw material value is the left endpoint value of the range value), and take the right endpoint values of the corresponding range values for the magnetic stirrer speed, reaction temperature, curing time, standing time, and the batch addition time of the mixed solution of MMA and BPO, etc.

[0040] Step 1: At room temperature, add 1000 g of water, 40 g of calcium-based bentonite, and 3 g of Na2CO3 into a container made of pp material, stir with a magnetic stirrer at a speed of 500 rpm, stir and mix the water, calcium-based bentonite, and Na2CO3 evenly, and then add 3 g of NaOH into the container and mix evenly to obtain the first mixed solution;

[0041] Step 2: Keep the stirring rate of the magnetic stirrer unchanged, add 2 g of MgCl2 into the first mixed solution, mix evenly and let it stand for 25 min to obtain the second mixed solution;

[0042] Step 3: Mix 45 g of MMA and 0.8 g of BPO to obtain a mixed solution of MMA and BPO. Heat the second mixed solution to 79 °C, and then add the mixed solution of MMA and BPO into the second mixed solution in three equal weight portions, stirring while adding, with an interval of 5 min for each addition. Adjust the speed of the magnetic stirrer to 1300 rpm and stir evenly for 0.8 h to obtain the third mixed solution;

[0043] Step 4: Adjust the speed of the magnetic stirrer to 900 rpm, add 5 g of lignosulfonate (dispersant) into the third mixed solution, cool down to 75 °C, stir for 0.5 h until the solution becomes transparent, stop heating, and let it stand for 2 h to obtain the fourth mixed solution;

[0044] Step 5: Keep the stirring rate of the magnetic stirrer unchanged, add 7 g of barite (weighting agent) and 25 g of sodium carboxymethylcellulose powder (CMC) with a molecular weight of 250000 g / mol into the fourth mixed solution, stir and mix evenly to obtain the CMC transparent slurry;

[0045] Step 6: Cure the prepared CMC transparent slurry: Stir at a constant speed of 600 rpm for 5 min every 3 h, and the curing time is 24 h.

[0046] Example 3

[0047] Prepare the raw materials according to water: calcium-based bentonite: Na2CO3: NaOH: MgCl2: MMA: BPO: dispersant: weighting agent: CMC = 100:5:0.5:0.5:0.3:6:0.12:0.8:1:3.5 (the raw material values are the right endpoint values of the range values), and take the right endpoint values of the corresponding range values for the magnetic stirrer speed, reaction temperature, curing time, standing time, and the batch addition time of the MMA and BPO miscible solution, etc. respectively.

[0048] Step 1: At room temperature, add 1000 g of water, 50 g of calcium-based bentonite, and 5 g of Na2CO3 into a pp material container, stir using a magnetic stirrer at a speed of 500 rpm, stir and mix the water, calcium-based bentonite, and Na2CO3 evenly, and then add 5 g of NaOH into this container and mix evenly to obtain the first mixed solution;

[0049] Step 2: Keep the stirring rate of the magnetic stirrer unchanged, add 3 g of MgCl2 into the first mixed solution, mix evenly and let it stand for 25 min to obtain the second mixed solution;

[0050] Step 3: Mix 60 g of MMA and 1.2 g of BPO to obtain a MMA and BPO miscible solution, heat the second mixed solution to 79 °C, and then add the MMA and BPO miscible solution into the second mixed solution in three equal weight portions, stir while adding, with an interval of 5 min for each addition, adjust the magnetic stirrer speed to 1300 rpm, and stir evenly for 0.8 h to obtain the third mixed solution;

[0051] Step 4: Adjust the magnetic stirrer speed to 900 rpm, add 8 g of lignosulfonate (dispersant) into the third mixed solution and cool it to 75 °C, stir for 0.5 h until the solution becomes transparent, stop heating, and let it stand for 2 h to obtain the fourth mixed solution;

[0052] Step 5: Keep the stirring rate of the magnetic stirrer unchanged, add 10 g of barite (weighting agent) and 35 g of sodium carboxymethylcellulose powder (CMC) with a molecular weight of 250000 g / mol into the fourth mixed solution, stir and mix evenly to obtain a CMC transparent slurry;

[0053] Step 6: Cure the prepared CMC transparent slurry: Stir evenly at 600 rpm for 5 min every 3 h, and the curing time is 24 h.

[0054] Example 4

[0055] Prepare the raw materials according to water: calcium-based bentonite: Na2CO3: NaOH: MgCl2: MMA: BPO: dispersant: weighting agent: CMC = 100:5:0.5:0.5:0.3:6:0.12:0.8:1:3.5 (the raw material values are the right endpoint values of the range), and take the left endpoint values of the corresponding ranges for the magnetic stirrer speed, reaction temperature, curing time, standing time, and the batch addition time of the MMA and BPO miscible solution respectively.

[0056] Step 1: At room temperature, add 1000 g of water, 50 g of calcium-based bentonite, and 5 g of Na2CO3 into a pp material container, stir using a magnetic stirrer at a speed of 500 rpm, mix the water, calcium-based bentonite, and Na2CO3 evenly, and then add 5 g of NaOH into this container and mix evenly to obtain the first mixed solution;

[0057] Step 2: Keep the stirring rate of the magnetic stirrer unchanged, add 3 g of MgCl2 into the first mixed solution, mix evenly and let it stand for 18 min to obtain the second mixed solution;

[0058] Step 3: Mix 60 g of MMA and 1.2 g of BPO to obtain the MMA and BPO miscible solution, heat the second mixed solution to 78 °C, and then add the MMA and BPO miscible solution into the second mixed solution in three equal weight portions, stirring while adding, with a time interval of 5 min for each addition, adjust the magnetic stirrer speed to 1000 rpm, and stir evenly for 0.5 h to obtain the third mixed solution;

[0059] Step 4: Adjust the magnetic stirrer speed to 700 rpm, add 8 g of lignosulfonate (dispersant) into the third mixed solution, cool down to 74 °C, stir for 0.3 h until the solution becomes transparent, stop heating, and let it stand for 1.5 h to obtain the fourth mixed solution;

[0060] Step 5: Keep the stirring rate of the magnetic stirrer unchanged, add 10 g of barite (weighting agent) and 35 g of sodium carboxymethyl cellulose powder (CMC) with a molecular weight of 250000 g / mol into the fourth mixed solution, stir and mix evenly to obtain the CMC transparent slurry;

[0061] Step 6: Cure the prepared CMC transparent slurry: Stir evenly at 600 rpm for 5 min every 3 h, and the curing time is 20 h.

[0062] Example 5

[0063] The weight ratio of each component is as follows: water: calcium-based bentonite: Na2CO3: NaOH: MgCl2: MMA: BPO: dispersant: weighting agent: CMC = 100:4:0.4:0.4:0.3:5:0.09:0.7:0.8:3. Prepare the raw materials, and take the left endpoint values of the corresponding range values for the magnetic stirrer speed, reaction temperature, curing time, standing time, and the batch addition time of the mixed solution of MMA and BPO, etc.

[0064] Step 1: At room temperature, add 1000 g of water, 40 g of calcium-based bentonite, and 4 g of Na2CO3 into a container made of pp material, stir with a magnetic stirrer at a speed of 500 rpm, mix the water, calcium-based bentonite, and Na2CO3 evenly, and then add 4 g of NaOH into this container and mix evenly to obtain the first mixed solution;

[0065] Step 2: Keep the stirring rate of the magnetic stirrer unchanged, add 3 g of MgCl2 into the first mixed solution, mix evenly and let it stand for 18 min to obtain the second mixed solution;

[0066] Step 3: Mix 50 g of MMA and 0.9 g of BPO to obtain a mixed solution of MMA and BPO. Heat the second mixed solution to 78 °C, and then add the mixed solution of MMA and BPO into the second mixed solution in three equal weight portions, stirring while adding, with an interval of 4 min for each addition. Adjust the speed of the magnetic stirrer to 1000 rpm and stir evenly for 0.5 h to obtain the third mixed solution;

[0067] Step 4: Adjust the speed of the magnetic stirrer to 700 rpm, add 7 g of lignosulfonate (dispersant) into the third mixed solution, cool down to 74 °C, stir for 0.3 h until the solution becomes transparent, stop heating, and let it stand for 1.5 h to obtain the fourth mixed solution;

[0068] Step 5: Keep the stirring rate of the magnetic stirrer unchanged, add 8 g of barite (weighting agent) and 30 g of sodium carboxymethyl cellulose powder (CMC) with a molecular weight of 250000 g / mol into the fourth mixed solution, stir and mix evenly to obtain a CMC transparent slurry;

[0069] Step 6: Cure the prepared CMC transparent slurry: Stir evenly at 500 rpm for 5 min every 2 h, and the curing time is 20 h.

[0070] Example 6

[0071] The weight ratios of the components are as follows: water: calcium-based bentonite: Na2CO3: NaOH: MgCl2: MMA: BPO: dispersant: weighting agent: CMC = 100:4:0.4:0.4:0.3:5:0.09:0.7:0.8:3. Prepare the raw materials, and take the right endpoint values of the corresponding ranges for the rotational speed of the magnetic stirrer, reaction temperature, curing time, standing time, and the batch addition time of the mixed solution of MMA and BPO, etc.

[0072] Step 1: At room temperature, add 1000 g of water, 40 g of calcium-based bentonite, and 4 g of Na2CO3 into a container made of pp material, and stir using a magnetic stirrer at a rotational speed of 500 rpm to mix the water, calcium-based bentonite, and Na2CO3 evenly. Then add 4 g of NaOH into this container and mix well to obtain the first mixed solution.

[0073] Step 2: Keep the stirring rate of the magnetic stirrer unchanged, add 3 g of MgCl2 into the first mixed solution, mix well, and let it stand for 25 min to obtain the second mixed solution.

[0074] Step 3: Mix 50 g of MMA and 0.9 g of BPO to obtain a mixed solution of MMA and BPO. Heat the second mixed solution to 79 °C, and then add the mixed solution of MMA and BPO into the second mixed solution in three equal weight portions, stirring while adding. The time interval between each addition is 5 min. Adjust the rotational speed of the magnetic stirrer to 1300 rpm and stir evenly for 0.8 h to obtain the third mixed solution.

[0075] Step 4: Adjust the rotational speed of the magnetic stirrer to 900 rpm, add 7 g of lignosulfonate (dispersant) into the third mixed solution, and cool it down to 75 °C. Stir for 0.5 h until the solution becomes transparent, stop heating, and let it stand for 2 h to obtain the fourth mixed solution.

[0076] Step 5: Keep the stirring rate of the magnetic stirrer unchanged, add 8 g of barite (weighting agent) and 30 g of sodium carboxymethyl cellulose powder (CMC) with a molecular weight of 250000 g / mol into the fourth mixed solution, and stir evenly to obtain a CMC transparent slurry.

[0077] Step 6: Cure the prepared CMC transparent slurry: Stir evenly at 500 rpm for 5 min every 2 h, and the curing time is 24 h.

[0078] Comparative Example 1

[0079] The proportions of each component are the same as those in Example 1, that is, the raw materials are prepared according to water: calcium-based bentonite: Na2CO3: NaOH: MgCl2: MMA: BPO: dispersant: weighting agent: CMC = 100:4:0.3:0.3:0.2:4.5:0.08:0.5:0.7:2.5 (the raw material values are the left endpoint values of the range values). The rotation speed of the magnetic stirrer, reaction temperature, curing time, standing time, the time for batch addition of the mixed solution of MMA and BPO, etc. are respectively taken as the left endpoint values of the corresponding range values. Change the addition method of the mixed solution of MMA and BPO in Step 3.

[0080] Step 1: At room temperature, add 1000 g of water, 40 g of calcium-based bentonite, and 3 g of Na2CO3 into a container made of pp material, and stir using a magnetic stirrer at a rotation speed of 500 rpm to mix the water, calcium-based bentonite, and Na2CO3 evenly. Then add 3 g of NaOH into this container and mix evenly to obtain the first mixed solution.

[0081] Step 2: Keep the stirring rate of the magnetic stirrer unchanged, add 2 g of MgCl2 into the first mixed solution, mix evenly, and let it stand for 18 min to obtain the second mixed solution.

[0082] Step 3: Mix 45 g of MMA and 0.8 g of BPO to obtain a mixed solution of MMA and BPO. Heat the second mixed solution to 78°C, and then add the mixed solution of MMA and BPO into the second mixed solution at one time. Adjust the rotation speed of the magnetic stirrer to 1000 rpm and stir evenly for 0.5 h to obtain the third mixed solution.

[0083] Step 4: Adjust the rotation speed of the magnetic stirrer to 700 rpm, add 5 g of lignosulfonate (dispersant) into the third mixed solution, and cool it to 74°C. Stir for 0.3 h until the solution becomes transparent, stop heating, and let it stand for 1.5 h to obtain the fourth mixed solution.

[0084] Step 5: Keep the stirring rate of the magnetic stirrer unchanged, add 7 g of barite (weighting agent) and 25 g of sodium carboxymethyl cellulose powder (CMC) with a molecular weight of 250000 g / mol into the fourth mixed solution, and stir evenly to obtain a transparent CMC slurry.

[0085] Step 6: Cure the prepared transparent CMC slurry: Stir evenly at 500 rpm for 5 min every 2 h, and the curing time is 20 h.

[0086] Comparative Example 2

[0087] The reaction steps, temperature conditions, etc. are the same as those in Example 1, but the contents of each component exceed the range given in the present invention. That is, the raw materials are prepared according to water: calcium-based bentonite: Na2CO3: NaOH: MgCl2: MMA: BPO: dispersant: weighting agent: CMC = 100: 6: 0.7: 0.7: 0.5: 3: 0.2: 0.9: 0.6: 2 (the raw material values are the left endpoint values of the range values). The rotation speed of the magnetic stirrer, reaction temperature, curing time, standing time, and the batch addition time of the mixed solution of MMA and BPO are respectively taken as the left endpoint values of the corresponding range values.

[0088] Step 1: At room temperature, add 1000 g of water, 60 g of calcium-based bentonite, and 7 g of Na2CO3 into a container made of pp material, and stir with a magnetic stirrer at a rotation speed of 500 rpm to mix the water, calcium-based bentonite, and Na2CO3 evenly. Then add 7 g of NaOH into the container and mix well to obtain the first mixed solution.

[0089] Step 2: Keep the stirring rate of the magnetic stirrer unchanged, add 0.5 g of MgCl2 into the first mixed solution, mix well and let it stand for 18 min to obtain the second mixed solution.

[0090] Step 3: Mix 30 g of MMA and 2 g of BPO to obtain a mixed solution of MMA and BPO. Heat the second mixed solution to 78 °C, and then add the mixed solution of MMA and BPO into the second mixed solution at one time. Adjust the rotation speed of the magnetic stirrer to 1000 rpm and stir evenly for 0.5 h to obtain the third mixed solution.

[0091] Step 4: Adjust the rotation speed of the magnetic stirrer to 700 rpm, add 9 g of lignosulfonate (dispersant) into the third mixed solution, cool it to 74 °C, stir for 0.3 h until the solution becomes transparent, stop heating, and let it stand for 1.5 h to obtain the fourth mixed solution.

[0092] Step 5: Keep the stirring rate of the magnetic stirrer unchanged, add 6 g of barite (weighting agent) and 20 g of sodium carboxymethyl cellulose powder (CMC) with a molecular weight of 250000 g / mol into the fourth mixed solution, and stir well, but a transparent CMC slurry cannot be obtained.

[0093] Comparative Example 2 shows that when the contents of each component exceed the range values limited by the present invention, a transparent CMC slurry cannot be obtained according to the method provided by the present invention.

[0094] Detect the transparent CMC slurries prepared in Examples 1-6 and Comparative Example 1

[0095] Permeability detection method: The CMC transparent slurries obtained in Examples 1-6 and Comparative Example 1 were respectively smeared on filter paper, and after drying, solidified mud skins were obtained. Flexible wall permeability tests were carried out on each solidified mud skin: The permeability coefficient K of the solidified mud was measured using a TST-50B type flexible wall permeameter (FWPT);

[0096] Viscosity detection method: The viscosities of the CMC transparent slurries obtained in Examples 1-6 and Comparative Example 1 were respectively detected, and the readings (Pa·s) of a six-speed (600 r / min) rotational viscometer were taken;

[0097] Transparency detection method: The transparencies of the CMC transparent slurries obtained in Examples 1-6 and Comparative Example 1 were respectively detected using a TM-2 transparency tester;

[0098] The test results are shown in Table 1:

[0099] Table 1 Test data of the CMC transparent slurries of Examples 1-6 and Comparative Example 1

[0100]

[0101] Result description: It can be seen from the test data of the CMC transparent slurries of Examples 1-6 and Comparative Example 1 that:

[0102] The permeability coefficient of the solidified mud skin prepared from the CMC transparent slurry prepared by the method proposed in Examples 1-6 is in the range of 1.40 - 1.5x10 -5 cm / s, with low water permeability, that is, good anti-permeability performance, which can prevent water in the soil trough wall from penetrating into the tunnel during shield tunneling; the viscosity of the CMC transparent slurry is between 17 and 20.3 Pa·s, with a high slurry viscosity. Coupled with the polymethyl methacrylate contained in the slurry, the mud skin formed by the slurry has high strength. During shield tunneling, a mud skin with very low water permeability will be formed on the soil trough wall, so that the hydrostatic pressure of the slurry can effectively act on the trough wall, preventing the trough wall from peeling off and playing a role in strengthening the trough wall; the transparency of the prepared CMC transparent slurry is between 308 - 315 mm, with high transparency, solving the problem that it is impossible to directly observe the movement state of the slag stones in the circulation system pipeline due to the turbid and opaque bentonite slurry used in construction.

[0103] By comparing Example 1 and Comparative Example 1, the permeability coefficient of Comparative Example 1 is greater than that of Example 1, and the transparency of Comparative Example 1 is lower than that of Example 1. It can be seen that the anti-permeability performance and transparency of the final slurry prepared by this method are related to the addition method of the MMA and BPO miscible solution in Step 3. Changing its addition method, the prepared slurry cannot meet the use requirements. As Figure 2 shown, Figure 2It is the scanning electron microscope (SEM) image of the transparent slurry prepared in the manner of Comparative Example 1. It can be seen that Figure 2 relatively large flocculent lumps appeared. This is because the polymerization rate of MMA and BPO was too fast, resulting in insufficient polymerization. The formed polymer combined with calcium-based bentonite to generate flocculent lumps, leading to uneven sizes of the components of the slurry and large gaps between the components, thus making its anti-permeation performance low. As Figure 3 shown, Figure 3 It is the scanning electron microscope (SEM) image of the transparent slurry prepared in the manner of Example 1. It can be seen that the gaps between the components are small and uniform, making its anti-permeation performance high.

[0104] In the description of the present invention, it should be understood that the terms "first", "second", "third", "fourth", "fifth" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features.

[0105] The above is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. A preparation method of CMC transparent slurry, characterized in that, It includes the following steps: Step 1: First, mix water, calcium-based bentonite and Na2CO3 evenly, and then add NaOH and mix evenly to obtain the first mixed solution; Step 2: Add MgCl2 to the first mixed solution, mix evenly and let it stand to obtain the second mixed solution; Step 3: Heat the second mixed solution to 78°C - 79°C, then add the mixed solution of MMA and BPO and stir. The mixed solution of MMA and BPO is added to the second mixed solution in three equal portions. Stir while adding, and the time interval between each addition is 4 - 5 minutes. Stir at a constant speed of 1000 - 1300 rpm for 0.5 - 0.8 h to obtain the third mixed solution; Step 4: Add a dispersant to the third mixed solution and cool it down to 74 - 75°C. Stir until the solution becomes transparent, stop heating, and let it stand to obtain the fourth mixed solution; Step 5: Add a weighting agent and CMC to the fourth mixed solution, and mix evenly to obtain the CMC transparent slurry.

2. The preparation method of a CMC transparent slurry according to claim 1, characterized in that, The preparation method also includes curing the obtained CMC transparent slurry. The curing method includes: Stir at a constant speed of 500 - 600 rpm for 5 minutes every 2 - 3 hours, and the curing time is 20 - 24 hours.

3. The preparation method of a CMC transparent slurry according to claim 1, characterized in that, The CMC is sodium carboxymethyl cellulose powder with a molecular weight of 250000 g / mol. The weighting agent includes barite and perlite. The dispersant includes lignosulfonate and compound phosphate.

4. The preparation method of a CMC transparent slurry according to claim 1, characterized in that, The weight ratio of each component is: water: calcium-based bentonite: Na2CO3: NaOH: MgCl2: MMA: BPO: dispersant: weighting agent: CMC = 100: 4 - 5: 0.3 - 0.5: 0.3 - 0.5: 0.2 - 0.3: 4.5 - 6: 0.08 - 0.12: 0.5 - 0.8: 0.7 - 1: 2.5 - 3.

5.

5. The preparation method of a CMC transparent slurry according to claim 4, wherein, The standing time in Step 2 is 18 - 25 minutes.

6. The preparation method of a CMC transparent slurry according to claim 4, characterized in that, In Step 4, stir at a constant speed of 700 - 900 rpm for 0.3 - 0.5 h until the solution becomes transparent, and the standing time is 1.5 - 2 h.

7. A method for preparing a CMC transparent slurry according to claim 1, characterized in that, The weight ratio of each component is: water: calcium-based bentonite: Na2CO3: NaOH: MgCl2: MMA: BPO: dispersant: weighting agent: CMC = 100: 4: 0.4: 0.4: 0.3: 5: 0.09: 0.7: 0.8:

3.

8. The CMC transparent slurry prepared by the preparation method of a CMC transparent slurry according to any one of claims 1 - 7.

9. The application of the CMC transparent slurry according to claim 8 in slurry shield construction or for replacing bentonite slurry in the slurry shield circulation system.

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