Thixotropic slurry and pipe jacking construction method based on thixotropic slurry

Abstract

The present invention belongs to the technical field of underground engineering construction, and specifically relates to a thixotropic mud and a pipe jacking construction method based on the thixotropic mud. The thixotropic mud includes the following components: a matrix, a stabilizer, a curing agent, a slow-release agent, and water; the curing agent includes a curing agent A and a curing agent B; the curing agent A is at least one of a soluble salt containing calcium, a soluble base containing calcium, a soluble salt containing magnesium, and a soluble base containing magnesium; the curing agent B is a salt, a salt solution, or a gas that can react with the curing agent A to form an insoluble precipitate; the curing agent B is embedded in a degradable material to form an embedding material, and exists independently of other components. The thixotropic mud has a self-hardening function while ensuring its lubricating effect. The pipe jacking construction method based on the thixotropic mud does not require thixotropic mud replacement, shortens the operation process, and reduces production costs.

Description

Technical Field

[0001] The invention belongs to the technical field of underground engineering construction, and particularly relates to a thixotropic slurry and a pipe jacking construction method based on the thixotropic slurry. Background Art

[0002] The construction of urban underground pipeline networks and underground transportation lines typically utilizes two methods: open-cut and underground construction. Open-cut construction often leads to damage to urban pavement, traffic congestion, and various environmental issues, including surface pollution and construction noise pollution, severely impacting the daily lives of urban residents. Underground construction methods include tunneling, pipe jacking, and shield tunneling. Pipe jacking, due to its economical, safe, efficient, and simple nature, has been widely used in the development and utilization of urban underground space.

[0003] The pipe jacking method requires the pipe to be pushed into the soil. In traditional construction methods, such as Figure 1 As shown in the figure, in order to reduce the resistance between the jacking pipe and the soil during jacking, it is usually necessary to inject thixotropic mud around the jacking pipe at the same time as the jacking pipe is inserted to play a lubricating role. Figure 2 As shown, the thixotropic slurry needs to be pushed out and replaced with a hardenable slurry (such as cement slurry) to improve the strength and stability of the pipe jacking structure.

[0004] However, in actual engineering, thixotropic slurry is often difficult to replace. The retained thixotropic slurry forms a weak layer around the jacking pipe, thereby reducing the stability of the jacking pipe structure. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention provides a thixotropic mud and a pipe jacking construction method based on the thixotropic mud, which avoids the construction link of mud replacement.

[0006] Specifically, the present invention provides the following technical solutions:

[0007] A thixotropic mud comprises the following components: a matrix, a stabilizer, a curing agent, a slow-release agent and water;

[0008] The curing agent includes curing agent A and curing agent B;

[0009] The curing agent A is at least one of a soluble salt containing calcium, a soluble base containing calcium, a soluble salt containing magnesium, and a soluble base containing magnesium;

[0010] The curing agent B is a salt, salt solution or gas that can react with the curing agent A to form an insoluble precipitate; the curing agent B is embedded in the degradable material to form an embedding material, and exists independently of other components.

[0011] In the present invention, a multi-component thixotropic mud system is formed by compounding a matrix, a stabilizer, a curing agent, a slow-release agent and water, and the components of the thixotropic mud system play a complementary role. Among them, the matrix is ​​the main component of the thixotropic mud. The matrix of the traditional thixotropic mud is usually bentonite. When it is dispersed in water, it has sufficient fluidity when disturbed, that is, thixotropy. However, due to the introduction of the stabilizer, the matrix of the new thixotropic mud proposed by the present invention can be ordinary soil and is no longer limited to bentonite. It can also be waste soil; the stabilizer in a suitable dosage range is used to improve the stability of the matrix and enhance its lubrication effect; the curing agent in a suitable dosage range gives the thixotropic mud a self-hardening function. The curing agent includes a curing agent A and a curing agent B embedded in a degradable material, and its degradation time is controlled by changing the composition of the degradable material and its wall thickness; the degradation time of the degradable material is further regulated by introducing a slow-release agent, that is, the release rate of the curing agent B is jointly regulated by the composition of the degradable material, its wall thickness and the slow-release agent. The components in this thixotropic mud system complement each other's advantages, giving the thixotropic mud good lubrication properties while enabling it to have self-hardening function, and the hardening time can be adjusted according to the construction cycle.

[0012] The present invention has no special restrictions on the type of matrix. It can be organic soil (mainly composed of organic matter), mineral soil (mainly composed of minerals such as quartz, feldspar, mica, such as kaolin), etc. It can also be waste earthwork generated by various civil construction projects. The matrix material is easy to obtain and low in cost.

[0013] In the present invention, the preferred weight ratio of each component is:

[0014]

[0015] Variable mud can take into account both excellent lubrication performance and self-hardening performance.

[0016] Preferably, the stabilizer is selected from at least one of sodium alginate, carrageenan, xanthan gum, and guar gum; the thixotropic mud of the present invention has a certain impact on the stability and lubrication effect of the matrix due to the addition of a curing agent and a sustained-release agent. Studies have found that the above-mentioned stabilizer is particularly suitable for being added to the thixotropic mud system of the present invention, which can not only improve the stability of the matrix, but also significantly enhance the lubrication effect of the thixotropic mud.

[0017] Preferably, the curing agent A is CaCl2 or Ca(OH)2, and the curing agent B is Na2CO3, Na2CO3 solution or CO2 gas.

[0018] Preferably, the degradable material is selected from at least one of starch-based materials (corn starch, wheat starch, potato starch, etc.) and polylactic acid.

[0019] Preferably, the method for preparing the embedding material comprises the following steps:

[0020] A) preparing the degradable material into a hot-melt tube;

[0021] B) filling curing agent B into the hot melt tube;

[0022] C) placing the hot melt tube under an inverted U-shaped hot press head of a hot press, and controlling the inverted U-shaped hot press head to press the hot melt tube downward, causing the upper and lower walls of the hot melt tube to melt and fuse together, and then rise above the inverted U-shaped hot press head, thereby forming a closed space containing curing agent B within the length of the inverted U-shaped hot press head;

[0023] D) moving the hot melt tube along its length by a certain length, and controlling the inverted U-shaped hot pressing head to press down on the hot melt tube, causing the upper and lower walls of the hot melt tube to melt and fuse together. The inverted U-shaped hot pressing head is then raised, and the above steps are repeated, thereby forming a plurality of closed spaces containing curing agent B in the hot melt tube;

[0024] E) cutting along the connection between two adjacent closed spaces to form a plurality of embedding objects containing curing agent B.

[0025] The method for preparing the embedding material used in the present invention has the advantages of fast molding speed, relatively simple production process and high production efficiency. In addition, the method relaxes the selection range of the curing agent B, and solid phase, liquid phase and gas phase can all be used for embedding material production.

[0026] Further preferably, the length of the inverted U-shaped hot press head ranges from 5 to 10 mm, and the inner diameter of the hot melt tube ranges from 5 to 10 mm. Studies have found that when the length and inner diameter are too large, the amount of embedding material added to the thixotropic slurry is small, resulting in uneven distribution of curing agent B and affecting the hardening effect of the thixotropic slurry. Furthermore, overly large embedding materials can easily clog the thixotropic slurry pumping system, affecting normal construction. When the length and inner diameter are too small, production becomes more difficult and an excessive amount of embedding material needs to be added to the thixotropic slurry, affecting the lubrication properties of the thixotropic slurry.

[0027] Preferably, the wall thickness of the hot melt tube is at least 2 mm. This thickness corresponds to the final wall thickness of the embedded material and is generally determined based on the construction period. If the construction period is long, the embedded material must not degrade rapidly, so a thicker wall thickness should be used. Conversely, if the construction period is short, a thinner wall thickness should be used to prevent the thixotropic slurry from hardening for a long time after completion. However, the wall thickness of the hot melt tube should be no less than 2 mm to prevent the embedded material from cracking due to a thinner wall thickness. This thickness should be determined based on the construction period.

[0028] Preferably, the sustained-release agent is selected from at least one of NaOH and KOH; more preferably, NaOH, which can achieve the purpose of regulating the degradation time without significantly affecting the lubrication effect of the thixotropic mud and the stability of the matrix.

[0029] The present invention also provides a pipe jacking construction method based on the above-mentioned thixotropic slurry, comprising the following steps:

[0030] 1) uniformly mixing ingredients including the matrix, stabilizer, curing agent A, embedding material containing curing agent B, sustained-release agent, and water to obtain a thixotropic slurry;

[0031] 2) During the jacking construction, the thixotropic slurry is injected into the outer side of the jacking pipe wall to play the role of lubrication and drag reduction;

[0032] 3) After the jacking construction is completed, the wall material of the embedded object gradually degrades, and the curing agent B contained in it is released into the thixotropic mud to react with the curing agent A, causing the thixotropic mud to harden and play a reinforcing role, thus eliminating the need to replace the thixotropic mud.

[0033] The beneficial effects of the present invention are at least:

[0034] 1) The novel thixotropic slurry provided by the present invention has a self-hardening function while ensuring its lubrication effect, and the hardening time can be adjusted according to the construction cycle;

[0035] 2) The present invention optimizes the dosage ratio of each component in the thixotropic slurry, so that the obtained thixotropic slurry can take into account both excellent lubrication performance and self-hardening performance;

[0036] 3) The present invention optimizes and selects at least one of sodium alginate, carrageenan, xanthan gum, and guar gum as a stabilizer, thereby improving the stability of the matrix and significantly enhancing the lubrication effect of the thixotropic slurry;

[0037] 4) By optimizing the method for preparing the investment, the present invention offers the advantages of rapid investment molding, relatively simple production processes, and high production efficiency. Furthermore, this method broadens the range of materials for curing agent B, allowing for investment production in solid, liquid, and vapor phases.

[0038] 5) The present invention optimizes the selection of NaOH as a sustained-release agent, which can achieve the purpose of regulating the degradation time without significantly affecting the lubrication effect of the thixotropic slurry and the stability of the matrix;

[0039] 6) The pipe jacking construction method provided by the present invention adopts the above-mentioned new thixotropic mud with self-hardening function, which eliminates the need to replace the thixotropic mud with a hardenable slurry, thereby solving the problem of difficult thixotropic mud ejection and replacement in traditional construction processes, shortening the operation process and reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0041] Figure 1 Schematic diagram of pipe jacking based on thixotropic mud.

[0042] Figure 2 Schematic diagram of replacing thixotropic mud after the pipe jacking construction is completed.

[0043] Figure 3 Schematic diagram of the preparation process of the embedding material.

[0044] Figure 4 It is a hot melt tube after hot pressing.

[0045] Figure 5 Schematic diagram of the structure of the embedded material.

[0046] Among them, 1-curing agent B, 2-hot melt pipe, 3-inverted U-shaped hot pressing head, 4-enclosed space, 5-embedded object, 6-jacking pipe, 7-thixotropic mud, 8-soil, and 9-cement slurry. DETAILED DESCRIPTION

[0047] The present invention will be described below by way of preferred embodiments. It will be appreciated by those skilled in the art that the embodiments are intended only to illustrate the present invention and are not intended to limit the scope of the present invention.

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not intended to limit the scope of the present invention. If no specific techniques or conditions are specified in the embodiments, the techniques or conditions described in the literature in the field or the product instructions shall be followed.

[0049] Example 1

[0050] This embodiment provides a novel thixotropic slurry, which contains the following components in parts by weight: 750 parts of matrix, 250 parts of stabilizer, 100 parts of curing agent A, 100 parts of curing agent B, 2 parts of sustained-release agent, and 6000 parts of water;

[0051] The matrix is ​​waste earthwork generated during construction at a construction site;

[0052] The stabilizer is sodium alginate;

[0053] Curing agent A is CaCl2;

[0054] Curing agent B is Na2CO3;

[0055] The sustained-release agent is NaOH.

[0056] The curing agent B is embedded in corn starch to form an embedding material, which can be seen in Figure 3 , the preparation method is as follows:

[0057] Corn starch was prepared into a hot melt tube with an inner diameter of 5 mm and a wall thickness of 2 mm;

[0058] Fill curing agent B into the hot melt tube;

[0059] After the power is turned on and the temperature is raised, the inverted U-shaped hot pressure head descends to squeeze the hot melt tube. The upper wall of the hot melt tube is softened by the heat after contacting the electric hot pressure head and is pressed down as the inverted U-shaped hot pressure head descends until it is tightly fitted with the lower wall of the hot melt tube. The upper and lower walls of the tightly fitted hot melt tube are melted and integrated by heat, thereby forming a closed space containing curing agent B within the length range of the inverted U-shaped hot pressure head (the length is 8mm). Then, the inverted U-shaped hot pressure head is lifted, and the hot melt tube is moved along the length direction to the closed space and crosses the length range of the inverted U-shaped hot pressure head. The above process is repeated, thereby forming several closed spaces containing curing agent B in the hot melt tube ( Figure 4 );

[0060] Cut along the connection between two adjacent closed spaces to form several embeddings containing curing agent B ( Figure 5 ).

[0061] The pipe jacking construction method based on the above-mentioned thixotropic slurry has the following steps:

[0062] 1) uniformly mixing ingredients comprising the matrix, stabilizer, curing agent A, embedding material comprising curing agent B, sustained-release agent, and water to obtain a thixotropic slurry;

[0063] 2) During the jacking construction, the thixotropic slurry is injected into the outer side of the jacking pipe wall from the grouting hole to fill the gap between the pipe section and the surrounding soil to play a role in lubrication and drag reduction;

[0064] 3) After the jacking construction is completed, the wall material of the embedded object gradually degrades, and the curing agent B contained in it is released into the thixotropic mud to react with the curing agent A, causing the thixotropic mud to harden and play a reinforcing role, thus eliminating the need to replace the thixotropic mud.

[0065] The new thixotropic mud provided in Example 1 has lower pipe-soil friction than traditional thixotropic mud, which can greatly reduce jacking resistance; at the same time, no water is separated after being left standing for 24 hours, and the stability is excellent.

[0066] The new thixotropic slurry provided in Example 1 can play a filling and supporting role equivalent to that of traditional replacement cement slurry after hardening, and can effectively avoid formation disturbance and settlement deformation.

[0067] Example 2

[0068] Compared with Example 1, the only difference is that Example 2 contains the following components in parts by weight: 750 parts of matrix, 500 parts of stabilizer, 125 parts of curing agent A, 125 parts of curing agent B, 3 parts of sustained-release agent, and 6000 parts of water.

[0069] The new thixotropic mud provided in Example 2 has lower pipe-soil friction than traditional thixotropic mud, which can greatly reduce jacking resistance; at the same time, no water is separated after being left standing for 24 hours, and the stability is excellent.

[0070] The new thixotropic slurry provided in Example 2 can play a filling and supporting role equivalent to that of traditional replacement cement slurry after hardening, and can effectively avoid formation disturbance and settlement deformation.

[0071] Example 3

[0072] Compared with Example 1, the only difference is that Example 3 contains the following components in parts by weight: 750 parts of matrix, 150 parts of stabilizer, 50 parts of curing agent A, 50 parts of curing agent B, 2 parts of sustained-release agent, and 6000 parts of water.

[0073] Compared with Example 1, the new thixotropic mud provided in Example 3 has a poor lubrication effect, and the friction with the formation is greater during the jacking process, making the jacking slightly difficult; the strong insoluble precipitate generated after hardening is insufficient, the thixotropic mud has a low degree of hardening, and has weak defects, which affects the stability of the jacking structure.

[0074] Comparative Example 1

[0075] Comparative Example 1 uses traditional thixotropic mud, which contains the following components: 10 wt % of bentonite, 0.5 wt % of sodium carbonate, 0.2 wt % of sodium carboxymethyl cellulose, and 89.3 wt % of water.

[0076] Comparative Example 2

[0077] Compared with Example 1, the only difference is that no stabilizer is added in Comparative Example 2.

[0078] The thixotropic mud provided in Comparative Example 2 caused excessive friction with the stratum during the jacking process, making the jacking construction very difficult.

[0079] When the pipe jacking construction depth (i.e., the buried depth of the pipe jacking) is 10m, the friction resistance corresponding to each working condition is shown in Table 1 below.

[0080] Table 1

[0081] Working conditions <![CDATA[Frictional resistance (kN / m 2 )]]> Comparative Example 1: Traditional thixotropic mud 19 Example 1 New thixotropic slurry 14.63 Example 2 New thixotropic slurry 11.97 Example 3 New thixotropic slurry 15.96

[0082] Note: The density of soil is about 19kN / m 3 .

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A thixotropic slurry, characterized in that: The invention comprises the following components: a matrix, a stabilizer, a curing agent, a sustained-release agent and water; The curing agent includes curing agent A and curing agent B; The curing agent A is at least one of a soluble salt containing calcium, a soluble base containing calcium, a soluble salt containing magnesium, and a soluble base containing magnesium; The curing agent B is a salt, salt solution or gas that can react with the curing agent A to form an insoluble precipitate; the curing agent B is embedded in the degradable material to form an embedding material, and exists independently of other components; The matrix is ​​organic soil, mineral soil or waste earth generated by various civil construction projects; The stabilizer is sodium alginate; The sustained-release agent is selected from at least one of NaOH and KOH; The degradable material is selected from at least one of starch-based materials and polylactic acid.

2. The thixotropic slurry according to claim 1, characterized in that: In parts by weight, it comprises the following components: 750 parts of matrix; 250-500 parts of stabilizer; Curing agent A 100-125 parts; Curing agent B 100-125 parts; 2-3 parts of sustained-release agent; 5000-7500 parts of water.

3. The thixotropic slurry according to claim 1 or 2, characterized in that: The curing agent A is CaCl2 or Ca(OH)2, and the curing agent B is Na2CO3, Na2CO3 solution or CO2 gas.

4. The thixotropic slurry according to claim 1 or 2, characterized in that: The method for preparing the embedding material comprises the following steps: A) preparing the degradable material into a hot-melt tube; B) filling curing agent B into the hot melt tube; C) placing the hot melt tube under the inverted U-shaped hot press head of the hot press, and controlling the inverted U-shaped hot press head to press the hot melt tube downward, causing the upper and lower walls of the hot melt tube to melt and fuse together, and then rise above the inverted U-shaped hot press head, thereby forming a closed space containing curing agent B within the length of the inverted U-shaped hot press head; D) Move the hot melt tube lengthwise for a certain length, and control the inverted U-shaped hot pressing head to press down on the hot melt tube, causing the upper and lower walls of the hot melt tube to melt and fuse together. Then, the inverted U-shaped hot pressing head is raised, and the above steps are repeated, thereby forming a plurality of closed spaces containing curing agent B in the hot melt tube; E) Cutting is performed along the connection between two adjacent closed spaces to form a plurality of embedding objects containing curing agent B.

5. The thixotropic slurry according to claim 4, characterized in that: The length range of the inverted U-shaped hot pressing head is 5-10 mm, and the inner diameter of the hot melt tube is 5-10 mm.

6. The thixotropic slurry according to claim 4, characterized in that: The wall thickness of the hot melt tube is greater than 2 mm.

7. A pipe jacking construction method based on the thixotropic slurry according to any one of claims 1 to 6, characterized in that: The following steps are involved: 1) uniformly mixing ingredients including the matrix, stabilizer, curing agent A, embedding material containing curing agent B, sustained-release agent, and water to obtain a thixotropic slurry; 2) During the jacking construction, the thixotropic slurry is injected into the outer side of the jacking pipe wall to play the role of lubrication and drag reduction; 3) After the jacking construction is completed, the wall material of the embedded object gradually degrades, and the curing agent B contained in it is released into the thixotropic mud to react with the curing agent A, causing the thixotropic mud to harden and play a reinforcing role, thus eliminating the need to replace the thixotropic mud.

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