Thixotropic slurry for pipe jacking of water-rich sandy gravel stratum and preparation method of thixotropic slurry

Abstract

The invention relates to the technical field of pipe jacking slurry materials, and particularly discloses thixotropic slurry for pipe jacking of a water-rich sandy gravel stratum and a preparation method of the thixotropic slurry. According to the thixotropic slurry, water, sodium bentonite, sodium carboxymethyl cellulose, vermiculite powder, anhydrous sodium carbonate, mica powder, nano silicon dioxide and polydimethylsiloxane are prepared according to a specific proportion to obtain the thixotropic slurry suitable for pipe jacking construction of the water-rich sandy gravel stratum. And a compact, complete, large-thickness and low-viscosity mud film is formed, the fluidity of the mud is effectively maintained under the condition that the consistency is improved while the effects of low filtration loss, resistance reduction and wall protection are achieved, and the resistance reduction effect is good. Under the grouting pressure, the thixotropic slurry can block pores of sandy pebbles, extrude and wrap a sandy pebble framework, fill and support the pores of the framework, reinforce a loose soil layer, resist high water pressure and effectively realize leaking stoppage and seepage reduction.

Description

Technical Field

[0001] The invention belongs to the field of pipe jacking mud materials, and particularly relates to thixotropic mud for pipe jacking in water-rich sand and gravel formations and a preparation method thereof. Background Art

[0002] As one of the key technologies in pipe jacking construction, the quality of thixotropic slurry is crucial to the success of the pipe jacking project. The main functions of thixotropic slurry are: (1) lubrication, reducing the friction between the pipe and the soil; (2) filling, filling the gaps between the pipe segment structure and the surrounding soil, making the contact surface smooth; (3) support, supporting the soil surrounding the pipe segment under the action of grouting pressure, reducing disturbance and deformation of the stratum, and ensuring a safe and controllable surrounding environment.

[0003] Under the geological conditions of sandy and gravel strata with high groundwater levels, when the undrained sinking method (underwater excavation) is used for sinking operations, the technical difficulty is that tilting is likely to occur during the sinking process, and correction is difficult; when the drainage sinking method (draining the groundwater and then excavating the soil) is used for sinking operations, it is necessary to lower the water level and add water-stop curtains such as cement mixing piles, which takes a long time and is costly.

[0004] Water-rich sand and gravel formations are a typical type of mechanically unstable formation with loose structure, large porosity, strong permeability, low cohesion, poor self-stabilization ability, and high water pressure. Due to the complex and harsh geological conditions of water-rich sand and gravel formations, higher requirements are placed on the performance of thixotropic mud: (1) First, thixotropic mud is required to have low filtration loss and to form a high-quality mud film in a short time; (2) Second, thixotropic mud is required to have high viscosity so that it can fill the larger pores of the sand and gravel formation without being carried away by water flow; (3) Finally, thixotropic mud is required to have good fluidity and drag reduction and lubrication, because mud with higher viscosity may deteriorate fluidity, and also to ensure that thixotropic mud can resist high water pressure under high injection pressure.

[0005] Currently, there are two types of thixotropic mud materials commonly used in pipe jacking in China: one is an inorganic material based on bentonite, and the other is based on synthetic polymer materials. The former is less polluting to groundwater, while the latter is more polluting. Research on inorganic thixotropic mud based on bentonite has mostly used sodium bentonite as the raw material, adding CMC, soda ash, and thickeners in varying proportions for different formations. After multiple rounds of testing and mix optimization, the optimal thixotropic mud ratio for different formation conditions is achieved. However, for high-water-pressure loose formations, such as water-rich sand and gravel formations, the current thixotropic mud is less effective and cannot meet the viscosity, fluidity, and other requirements of high-water-pressure loose formations. Therefore, specialized thixotropic mud development is needed for such complex formations. Summary of the Invention

[0006] Aiming at the defects and problems of poor effect of current common thixotropic mud in water-rich sand and gravel formations, the present invention provides a thixotropic mud for pipe jacking in water-rich sand and gravel formations and a preparation method thereof.

[0007] The invention provides a thixotropic mud for pipe jacking in a water-rich sand and gravel formation. The thixotropic mud comprises the following raw materials in parts by weight: 950-1050 parts of water, 85-95 parts of sodium bentonite, 1.8-2.2 parts of sodium carboxymethyl cellulose, 2.7-3.2 parts of anhydrous sodium carbonate, 15-18 parts of nano-silicon dioxide, and 3.5-4.5 parts of polydimethylsiloxane.

[0008] The thixotropic mud for pipe jacking in water-rich sand and gravel formations comprises the following raw materials in parts by weight: 1000 parts of water, 90 parts of sodium bentonite, 2 parts of sodium carboxymethyl cellulose, 3 parts of anhydrous sodium carbonate, 16 parts of nano-silicon dioxide, and 4 parts of polydimethylsiloxane.

[0009] The thixotropic mud for pipe jacking in water-rich sand and gravel formations is characterized in that the nano-silica is hydrophobic spherical nano-silica.

[0010] The thixotropic mud for pipe jacking in water-rich sand and gravel formations has a particle size of nano-silicon dioxide of 17-40 nm.

[0011] The thixotropic mud for pipe jacking in water-rich sand and gravel formations further comprises vermiculite powder, wherein the vermiculite powder is in the form of particles of 1-4 mm.

[0012] The thixotropic mud for pipe jacking in water-rich sand and gravel formations further comprises mica powder, which is flaky mica powder with a diameter of 2-4 mm.

[0013] The thixotropic slurry for pipe jacking in water-rich sand and gravel formations mentioned above has the vermiculite powder added in an amount of 5%-10% of the sodium bentonite.

[0014] In the above-mentioned thixotropic slurry for pipe jacking in water-rich sand and gravel formations, the added amount of the mica powder is 5%-10% of the sodium bentonite.

[0015] The present invention also provides a method for preparing thixotropic mud for pipe jacking in water-rich sand and gravel formations, comprising the following steps:

[0016] S1. Weigh the above raw materials by weight, add sodium bentonite and water into a blender, stir for 1-3 hours, and let it stand for 12-24 hours to fully hydrate the sodium bentonite;

[0017] S2, continue stirring after full hydration, add sodium carboxymethyl cellulose, mica powder, anhydrous sodium carbonate, vermiculite powder and nano-silica while stirring, stir evenly and let stand;

[0018] S3. Add polydimethylsiloxane, stir evenly and let it stand.

[0019] In the above-mentioned method for preparing thixotropic mud for pipe jacking in water-rich sand and gravel formations, in step S2, the slurry is stirred for 1-3 hours and then allowed to stand for 4-6 hours.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The thixotropic mud for pipe jacking in water-rich sand and gravel formations provided by the present invention can cement solid-phase materials under grouting pressure in water-rich sand and gravel formations with many pores and cracks, change the internal structure of the mud, and combine solid particles into large particles and then form sediment blocks. It can quickly form a dense mud jacket around the pipe joint in high-water-pressure loose formations.

[0022] 2. The thixotropic mud for pipe jacking in water-rich sand and gravel formations provided by the present invention has good rheological and thixotropic properties, and the mud film formed is dense and complete, with a large thickness and low viscosity, and has a good drag reduction and lubrication effect.

[0023] 3. The thixotropic mud prepared by the present invention through the synergistic effect of various components can effectively solve the problem of poor fluidity caused by increased mud consistency, effectively maintain the fluidity of the mud while increasing the consistency, and have a good drag reduction effect.

[0024] 4. The large-particle sediment blocks formed by the thixotropic mud prepared by the present invention can gradually block the pores of sand and gravel under grouting pressure and squeeze and entrain the sand and gravel skeleton, thereby reinforcing the loose soil layer, resisting high water pressure under high injection pressure, and effectively achieving leak plugging and seepage reduction.

[0025] 5. The nano-silicon dioxide added to the thixotropic mud of the present invention has high thermal stability and chemical inertness, and its properties are not easily changed at high temperatures. When added to the mud, it can form physical and chemical bonds with other components in the mud, thereby enhancing the overall mechanical strength of the mud and improving its compressive and shear resistance at high temperatures. At the same time, its high specific surface area can form a large number of contact points and microstructure networks in the mud, thereby enhancing the interaction force inside the mud and preventing structural collapse under high temperature conditions, and its excellent dispersibility enables it to effectively fill the tiny gaps in the mud, thereby enhancing the compactness and strength of the mud, which is beneficial to improving temperature resistance.

[0026] 6. The thixotropic slurry prepared by the present invention is easy to prepare, and the materials used are all environmentally friendly materials with little pollution to groundwater.

[0027] 7. The thixotropic mud prepared by the present invention always maintains stable properties during the grouting flow process, and will not segregate or stratify. At the same time, it has good rheological properties when it has sufficient viscosity, which is convenient for pumping, effectively ensuring the normal progress of grouting. The drag-reducing and lubricating effect of the thixotropic mud can reduce the friction resistance around the pipe body during the jacking process, increase the single jacking length, and improve construction efficiency.

[0028] 8. The thixotropic mud prepared by the present invention forms a dense and complete mud film through the synergistic effect between bentonite mud, inert materials, nano-silica and polydimethylsiloxane, with large thickness, low viscosity and good drag reduction and lubrication effect. While having low filtration loss and drag reduction and wall protection effects, the thixotropic mud can effectively reside in the pores in water-rich sand and gravel formations by utilizing the bridging effect between the inert materials and the bentonite slurry, thereby achieving the purpose of filling, supporting and improving impermeability. DETAILED DESCRIPTION

[0029] To address the problem that current thixotropic mud for pipe jacking has poor performance in loose formations such as water-rich sand and gravel formations, the present invention provides a thixotropic mud for pipe jacking in water-rich sand and gravel formations and a preparation method thereof. The present invention will be further described below with reference to embodiments.

[0030] Example 1: This example provides a thixotropic mud for pipe jacking in water-rich sand and gravel formations, comprising 1000 g of water, 90 g of sodium bentonite, 2 g of sodium carboxymethyl cellulose, 3 g of anhydrous sodium carbonate, 16 g of nano-silica, and 4 g of polydimethylsiloxane; wherein the nano-silica is hydrophobic spherical nano-silica with a particle size of 17-40 nm.

[0031] Preparation method:

[0032] First, sodium bentonite and water were added into a mixer and stirred for 1 hour, and then allowed to stand for 24 hours to allow the sodium bentonite to fully hydrate.

[0033] Then continue stirring, add sodium carboxymethyl cellulose, anhydrous sodium carbonate and nano-silicon dioxide while stirring, stir for 1 hour and then let it stand for 6 hours;

[0034] Finally, add polydimethylsiloxane, stir evenly, and let it stand for 1 hour.

[0035] Example 2: This example provides a thixotropic mud for pipe jacking in a water-rich sand and gravel formation, comprising 950 g of water, 90 g of sodium bentonite, 2.2 g of sodium carboxymethyl cellulose, 3 g of anhydrous sodium carbonate, 16 g of nano-silica, and 4 g of polydimethylsiloxane.

[0036] The preparation method is the same as that of Example 1.

[0037] Example 3: This example provides a thixotropic mud for pipe jacking in a water-rich sand and gravel formation, comprising 1000 g of water, 85 g of sodium bentonite, 2 g of sodium carboxymethyl cellulose, 3.2 g of anhydrous sodium carbonate, 18 g of nano-silica, and 4 g of polydimethylsiloxane.

[0038] The preparation method is the same as that of Example 1.

[0039] Example 4: This example provides a thixotropic mud for pipe jacking in a water-rich sand and gravel formation, comprising 1050 g of water, 85 g of sodium bentonite, 2.2 g of sodium carboxymethyl cellulose, 3.2 g of anhydrous sodium carbonate, 15 g of nano-silica, and 4.5 g of polydimethylsiloxane.

[0040] The preparation method is the same as that of Example 1.

[0041] Example 5: This example provides a thixotropic mud for pipe jacking in water-rich sand and gravel formations, including 1050g of water, 85g of sodium bentonite, 1.8g of sodium carboxymethyl cellulose, 3.2g of anhydrous sodium carbonate, 16g of nano-silica, and 3.5g of polydimethylsiloxane.

[0042] The preparation method is the same as that of Example 1.

[0043] Example 6: This example provides a thixotropic mud for pipe jacking in a water-rich sand and gravel formation, comprising 1000 g of water, 90 g of sodium bentonite, 2 g of sodium carboxymethyl cellulose, 3 g of anhydrous sodium carbonate, 18 g of nano-silica, and 4.5 g of polydimethylsiloxane.

[0044] The preparation method is the same as that of Example 1.

[0045] Example 7: This example provides a thixotropic mud for jacking pipes in water-rich sand and gravel formations, including 1000g water, 90g sodium bentonite, 5g mica powder, 2g sodium carboxymethyl cellulose, 3g anhydrous sodium carbonate, 16g nano-silica, 5g vermiculite powder, and 4g polydimethylsiloxane.

[0046] Preparation method:

[0047] First, sodium bentonite and water were added into a mixer and stirred for 1 hour, and then allowed to stand for 24 hours to allow the sodium bentonite to fully hydrate.

[0048] Then continue stirring, add sodium carboxymethyl cellulose, mica powder, anhydrous sodium carbonate, vermiculite powder and nano-silicon dioxide while stirring, stir for 1 hour and then let it stand for 6 hours; wherein the particle size of the mica powder is 2-4mm flakes, and the vermiculite powder is 1-4mm particles;

[0049] Finally, add polydimethylsiloxane, stir evenly, and let it stand for 1 hour.

[0050] Example 8: This example provides a thixotropic mud for jacking pipes in water-rich sand and gravel formations, including 1000g of water, 80g of sodium bentonite, 5g of mica powder, 2g of sodium carboxymethyl cellulose, 3g of anhydrous sodium carbonate, 16g of nano-silica, 5g of vermiculite powder, and 4g of polydimethylsiloxane; the preparation method is the same as that of Example 7.

[0051] Comparative Example 1: This comparative example provides a thixotropic mud, which is prepared by adding 1000g of water and 90g of sodium bentonite into a mixing container and stirring for 1h, and letting it stand for 24h to fully hydrate the bentonite; then, adding 2g of sodium carboxymethyl cellulose and 3g of anhydrous sodium carbonate while stirring the mud, stirring for 1h, and letting it stand for 6h to fully dissolve them.

[0052] Comparative Example 2: This comparative example provides a thixotropic mud, which is prepared by adding 1000 g of water and 90 g of sodium bentonite into a mixing container and stirring for 1 hour, and letting it stand for 24 hours to fully hydrate the bentonite; then, adding 2 g of sodium carboxymethyl cellulose, 3 g of anhydrous sodium carbonate, and 2 g of polyacrylamide while stirring the mud, stirring for 1 hour, and letting it stand for 6 hours to fully dissolve them.

[0053] Comparative Example 3: This comparative example provides a thixotropic mud, which is prepared by adding 1000g of water and 90g of sodium bentonite into a mixing container and stirring for 1h, and letting it stand for 24h to fully hydrate the bentonite; then, adding 2g of sodium carboxymethyl cellulose, 3g of anhydrous sodium carbonate, and 16g of nano-silica while stirring the mud, stirring for 1h, and letting it stand for 6h to fully dissolve them.

[0054] Comparative Example 4: This comparative example provides a thixotropic mud. 1000g of water and 90g of sodium bentonite are added to a mixing container and stirred for 1h, and then allowed to stand for 24h to fully hydrate the bentonite; then 2g of sodium carboxymethyl cellulose and 3g of anhydrous sodium carbonate are added while stirring the mud, stirred for 1h, allowed to stand for 6h, and finally 4g of polydimethoxysiloxane is added, stirred evenly, and allowed to stand for 1h.

[0055] Comparative Example 5: This embodiment provides a thixotropic mud, including 1000g of water, 90g of sodium bentonite, 2g of sodium carboxymethyl cellulose, 3g of anhydrous sodium carbonate, 16g of nano-silica, and 6g of polydimethylsiloxane.

[0056] Comparative Example 6: This embodiment provides a thixotropic mud, including 1000g of water, 90g of sodium bentonite, 2g of sodium carboxymethyl cellulose, 3g of anhydrous sodium carbonate, 20g of nano-silica, and 4g of polydimethylsiloxane.

[0057] Test Example 1: The wall protection, thixotropy and fluidity of the thixotropic slurries prepared in the examples and comparative examples were tested, and the results were as follows.

[0058] (1) The density, pH value and water separation rate of the thixotropic mud were measured. At the same time, a medium-pressure water loss meter was used to measure the filtration loss and mud skin thickness of the thixotropic mud by timing the pressure gauge reading for 30 minutes when it stabilized at 0.7 MPa. The results are shown in Table 1 below.

[0059] Table 1 Performance test results of thixotropic mud in different test groups

[0060]

[0061]

[0062] It can be seen from the results that the thixotropic mud prepared by the present invention has a lower filtration loss, and after adding nano-silica and polydimethylsiloxane to the bentonite-based slurry, it has better thixotropy and lower filtration loss than the bentonite slurry, and can form a dense and thick mud jacket, which has obvious wall protection and leak-proofing and anti-seepage effects.

[0063] (2) The thixotropy (yield value) and fluidity of the thixotropic mud were measured using a six-speed rotary viscometer. The results are shown in Table 2 below.

[0064] Table 2 Thixotropy and fluidity of thixotropic mud in different test groups

[0065]

[0066]

[0067] As can be seen from the above results, the thixotropic mud of the present invention has a higher consistency coefficient, can meet the demand of the rich water sand and gravel stratum for consistency, can fill the pores of the sand and gravel stratum without being carried away by water flow, mainly in that adding nano silicon dioxide in bentonite mud can form the mud particle group into large particle deposition, quickly form a dense and thick mud cover, while the nano particle size is small and dispersed and stable, reduce the dispersibility of clay minerals, reduce mud viscosity. And add a small amount of inert materials such as flaky mica powder and granular vermiculite powder, utilize the bridging effect of inert materials and bentonite slurry to make thixotropic mud effectively reside in the pores and enclose pebble in the rich water sand and gravel stratum, play the purpose of filling support and improving impermeability. Simultaneously, the addition of mica powder cooperates with polydimethylsiloxane to adhere to the mud film surface to improve the lubricity of mud, improves suspension and stability while reducing mud film water permeability, and makes thixotropic mud still have good fluidity when having the consistency of meeting loose stratum. The synergistic effect of various components can improve the thixotropy, stability and resistance seepage reduction of the mud while solving the problem of poor fluidity caused by the increase in consistency of the current thixotropic mud, and achieve better drag reduction effect.

[0068] Test Example 2: Based on the measurement results of Test Example 1, this test example selected the thixotropic mud prepared in Example 1, Implementation Example 7, Example 8 and Comparative Example 1, Comparative Example 2, and mixed them with mud and sand in a ratio of 1:1 to prepare mortar-sand gel specimens. The permeability coefficient of the mortar gel specimen was determined by a variable head penetration test. The results are shown in Table 3 below.

[0069] Table 3 Impermeability of thixotropic mud in different test groups

[0070]

[0071]

[0072] It can be seen from Table 3 that the thixotropic mud prepared by the present invention has a significantly lower permeability coefficient than the existing thixotropic mud, and can achieve excellent plugging and anti-seepage effect in water-rich sand and gravel formations. The thixotropic mud with the addition of mica powder and vermiculite powder can not only form a mud skin with a denser structure, but also the anti-seepage property of the thixotropic mud does not change significantly after the amount of bentonite added is reduced. To a certain extent, it shows that the addition of mica powder and vermiculite can reduce the amount of bentonite used, effectively save the hydration time of bentonite, improve quality and efficiency, and mica powder and polydimethylsiloxane synergistically improve the drag reduction and lubrication effect of the thixotropic mud, thereby reducing the friction resistance around the pipe body during the jacking process, increasing the single jacking length, and improving construction efficiency.

[0073] Test Example 3: In this test example, the high temperature resistance test of the thixotropic mud prepared in Example 1, Implementation Example 7, Example 8 and Comparative Example 1 and Comparative Example 2 was carried out. Specifically, equal amounts of the above mud samples were taken and placed in corresponding stainless steel sample cups and stirred evenly. After covering, the sample cups were placed in a high-temperature furnace, heated to 75°C and kept constant. After standing for 1 hour, they were taken out and the yield value and filtration loss of the mud were measured. The results are shown in Table 4 below.

[0074] Table 4 Yield values ​​of different thixotropic slurries after treatment in a 75℃ high temperature furnace

[0075]

[0076] As can be seen from Table 4, after the thixotropic mud prepared by the present invention is treated at a high temperature of 75°C, the thixotropy (yield value) and the filtration loss do not change significantly, indicating that the thixotropic mud has excellent high temperature resistance and can resist the friction heat between the concrete pipe and the formation. Even if the temperature between the concrete and the formation rises due to friction during the jacking construction, the thixotropic mud can still maintain good thixotropy and lubrication. This may be related to the addition of nano-silica and polydimethylsiloxane. Nano-silica has high thermal stability and chemical inertness, and its properties are not easily changed at high temperatures. When added to the mud, it can The other components in the slurry undergo physical and chemical bonding, which enhances the overall mechanical strength of the slurry and improves its compressive and shear resistance at high temperatures. At the same time, its high specific surface area can form a large number of contact points and microstructure networks in the slurry, enhancing the interaction force within the mud to prevent structural collapse under high temperature conditions. Its excellent dispersibility can effectively fill the tiny gaps in the mud, enhancing the compactness and strength of the mud, which is beneficial to improving temperature resistance. Polydimethylsiloxane itself has excellent thermal stability, which to a certain extent also provides a basis for improving the high-temperature resistance of thixotropic mud.

[0077] The above description is only a preferred embodiment of the present invention and does not limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A thixotropic slurry for pipe jacking in water-rich sand and gravel formations, characterized by: The invention comprises the following raw materials in parts by weight: 950-1050 parts of water, 80-95 parts of sodium bentonite, 1.8-2.2 parts of sodium carboxymethyl cellulose, 2.7-3.2 parts of anhydrous sodium carbonate, 15-18 parts of nano silicon dioxide and 3.5-4.5 parts of polydimethylsiloxane.

2. The thixotropic mud for pipe jacking in water-rich sand and gravel formations according to claim 1 is characterized by: The invention comprises the following raw materials in parts by weight: 1000 parts of water, 90 parts of sodium bentonite, 2 parts of sodium carboxymethyl cellulose, 3 parts of anhydrous sodium carbonate, 16 parts of nano silicon dioxide and 4 parts of polydimethylsiloxane.

3. The thixotropic mud for pipe jacking in water-rich sand and gravel formations according to claim 1 is characterized by: The nano-silica is hydrophobic spherical nano-silica.

4. The thixotropic mud for pipe jacking in water-rich sand and gravel formations according to claim 1 is characterized by: The nano-silicon dioxide particle size is 17-40 nm.

5. The thixotropic mud for pipe jacking in water-rich sand and gravel formations according to claim 1 is characterized by: The invention also comprises vermiculite powder, wherein the vermiculite powder is in the form of 1-4 mm particles.

6. The thixotropic mud for pipe jacking in water-rich sand and gravel formations according to claim 5 is characterized by: The added amount of the vermiculite powder is 5%-10% of the sodium bentonite.

7. The thixotropic mud for pipe jacking in water-rich sand and gravel formations according to claim 1 is characterized by: The invention also comprises mica powder, wherein the mica powder is flaky mica powder with a diameter of 2-4 mm.

8. The thixotropic mud for pipe jacking in water-rich sand and gravel formations according to claim 7 is characterized by: The added amount of the mica powder is 5%-10% of the sodium bentonite.

9. The method for preparing thixotropic slurry for pipe jacking in water-rich sand and gravel formations according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Weigh the above raw materials by weight, add sodium bentonite and water into a blender, stir for 1-3 hours, and let it stand for 12-24 hours to fully hydrate the sodium bentonite; S2, continue stirring after full hydration, add sodium carboxymethyl cellulose, mica powder, anhydrous sodium carbonate, vermiculite powder and nano-silica while stirring, stir evenly and let stand; S3. Add polydimethylsiloxane, stir evenly and let it stand.

10. The method for preparing thixotropic slurry for pipe jacking in water-rich sand and gravel formations according to claim 9, characterized in that: In step S2, the mixture is stirred for 1-3 hours and then allowed to stand for 4-6 hours.

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