Application of phase change material to replace thixotropic mud in pipe jacking construction, Pipe jacking construction method based on phase change material
By using phase change materials in pipe jacking construction and controlling their phase change characteristics by temperature, the problem of traditional thixotropic mud being difficult to replace was solved, achieving a dual improvement in the stability and lubrication effect of the pipe jacking structure.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TIANJIN UNIV
- Filing Date
- 2025-09-26
- Publication Date
- 2026-07-03
AI Technical Summary
Traditional thixotropic mud is difficult to replace in pipe jacking construction, which leads to a decrease in the stability of the pipe jacking structure.
Phase change materials are used to replace thixotropic mud. By controlling the temperature, the liquid and solid states are adjusted. The lubrication and drag reduction effects and the solidification and reinforcement effects of phase change materials are utilized to avoid displacement problems.
This achieves a dual guarantee of stability and lubrication effect for the pipe jacking structure, reduces construction energy consumption, and improves construction efficiency.
Smart Images
Figure CN120867769B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of underground engineering construction technology, specifically involving the application of phase change materials in pipe jacking construction to replace thixotropic mud, and a pipe jacking construction method based on phase change materials. Background Technology
[0002] The construction of urban underground pipe networks and underground transportation lines typically employs two methods: open-cut construction and underground construction. Open-cut construction often leads to damage to urban road surfaces, traffic congestion, and various environmental problems such as urban surface pollution and construction noise pollution, severely impacting the daily lives of urban residents. Underground construction includes methods such as tunneling, pipe jacking, and shield tunneling.
[0003] Pipe jacking construction requires pushing a pipe into the soil. In traditional construction methods, such as... Figure 1 As shown, to reduce the resistance between the jacking pipe and the soil during jacking, thixotropic mud is usually injected around the jacking pipe at the same time as jacking, to provide lubrication. After construction is completed, as... Figure 2 As shown, the thixotropic mud needs to be ejected and replaced with a hardenable grout (such as cement grout) to improve the strength and stability of the pipe jacking structure.
[0004] However, in actual engineering projects, thixotropic mud is often difficult to remove and replace. The retained thixotropic mud forms a weak layer around the jacking pipe, thereby reducing the stability of the jacking pipe structure. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides the application of phase change materials in pipe jacking construction to replace thixotropic mud, and a pipe jacking construction method based on phase change materials, thus avoiding the construction step of mud replacement.
[0006] Specifically, the present invention provides the following technical solutions:
[0007] The application of phase change materials to replace thixotropic mud in pipe jacking construction. The phase change materials are selected from one or more of paraffin wax, fatty acid solid-liquid phase change materials and fatty alcohol solid-liquid phase change materials (which are liquid at high temperature and harden into solid at room temperature).
[0008] Phase change materials (PCMs) are materials that can absorb and release a large amount of latent heat of phase change during a phase transition. Based on the phase change mechanism, PCMs can be classified into four main categories: solid-solid, solid-gas, liquid-gas, and solid-liquid. Among these, solid-liquid PCMs have become a research hotspot in recent years due to their advantages such as small volume change before and after the phase change, large latent heat of phase change, wide phase change temperature range, good stability, and low cost. Commonly used solid-liquid PCMs include paraffin wax, fatty acids, fatty alcohols, and inorganic hydrated salts, mainly used for temperature regulation and energy storage.
[0009] The inventors of this invention creatively employ phase change materials to replace thixotropic mud in pipe jacking construction, and conveniently control the phase (liquid / solid) of the phase change material by adjusting the pipe jacking temperature. The liquid phase change material can be easily injected around the pipe jacking to provide lubrication and drag reduction, similar to traditional thixotropic mud, while the solid phase change material acts as a hardening slurry, providing strength to ensure the stability of the pipe jacking structure, thus avoiding the problem of difficulty in replacing traditional thixotropic mud.
[0010] In this invention, the fatty acid-based solid-liquid phase change material is preferably a fatty acid with 10 or more carbon atoms, and the fatty alcohol-based phase change material is preferably a fatty alcohol with 14 or more carbon atoms. If the number of carbon atoms is too small, the molecular chain is short, the melting point is usually low, and it cannot remain solid at room temperature.
[0011] Preferably, the phase change material includes two or more phase change materials with different melting points, wherein the first phase change material has the highest melting point, the second phase change material has a lower melting point than the first phase change material, and so on (for example, it includes four phase change materials, wherein the first phase change material has the highest melting point, the second phase change material has a lower melting point than the first phase change material, the third phase change material has a lower melting point than the second phase change material, and the fourth phase change material has a lower melting point than the third phase change material).
[0012] This invention utilizes a phase change material (PCM) composite composed of various PCM materials with different melting points for pipe jacking construction. As the temperature increases, a greater proportion of this PCM composite melts (for example, when the temperature rises to 35°C, the PCM materials with melting points below 35°C melt; as the temperature continues to rise to 40°C, the PCM materials with melting points below 40°C melt, and so on). Using this PCM composite, the degree of melting can be controlled by adjusting the temperature. Different projects are located in different geological formations, resulting in varying pipe jacking resistance. If a project requires a higher level of lubrication, a higher temperature is used to melt a larger proportion of the PCM materials. Conversely, if a slightly lower level of lubrication is sufficient, a lower temperature is used to melt a smaller proportion of the PCM materials to conserve energy. Furthermore, this invention employs two or more phase change materials with different melting points. If the outer wall of the jacking pipe is heated to a temperature at which only the phase change material with the lower melting point can melt during the jacking construction, then after all the liquefied phase change material is injected into the outer wall of the jacking pipe through the grouting hole, the other part of the phase change material with the higher melting point will solidify. This can provide a certain strength while ensuring the lubrication effect, thereby limiting the displacement of the jacking pipe from the jacking axis (such as settlement displacement) to a certain extent during the jacking construction, and also limiting the infiltration of the liquid phase change material into the surrounding soil to a certain extent.
[0013] More preferably, the melting point of the second phase change material is 5-10°C lower than that of the first phase change material, and so on (for example, including four phase change materials, the melting point of the second phase change material is 5-10°C lower than that of the first phase change material, the melting point of the third phase change material is 5-10°C lower than that of the second phase change material, and the melting point of the fourth phase change material is 5-10°C lower than that of the third phase change material). If the difference in melting points is too small, the precision requirement for temperature control during construction is high, increasing the difficulty of construction; if the difference in melting points is too large, the melting ratio of the phase change material composite can provide is limited, that is, the selectivity of the lubrication provided for construction is limited. In addition, the melting point of the phase change material with the lowest melting point should not be lower than 30°C, so as to prevent it from remaining liquid at room temperature and failing to solidify, or from melting into liquid when encountering an accidental heat source during the service life of the jacking pipe, affecting the stability of the jacking pipe structure.
[0014] More preferably, the volume content of each phase change material in the two or more phase change materials with different melting points is 20% or more (based on the total volume of all liquefied phase change materials). In a most preferred embodiment, the phase change material includes two phase change materials with different melting points, and the volume ratio (in liquid state) of the first phase change material and the second phase change material is 40~60:40~60.
[0015] Preferably, the phase change material contains mineral soil as an additive. Studies have found that after the phase change material melts upon heating, it easily seeps into the surrounding soil, leading to material loss. Furthermore, after cooling and solidifying, the mechanical strength of the phase change material is too low (weak and easily deformed) and it cannot provide sufficient frictional resistance to limit the displacement of the jacking pipe (for example, paraffin wax can still be used as a lubricant in its solid state). This invention, by incorporating a certain amount of mineral soil into the phase change material, overcomes these drawbacks, improves its solid-state strength, and at the same time has almost no impact on its lubrication and drag reduction effects in the liquid state.
[0016] Preferably, the mineral soil is selected from one or more of bentonite, kaolinite, and diatomite.
[0017] Preferably, the mineral soil content is 100-185% based on the mass of the phase change material. At this content, the resulting phase change material can achieve both excellent liquid lubrication performance and solid strength. If the content is too high, the liquid lubrication performance will decrease significantly; if the content is too low, the phase change material will easily leak into the surrounding soil in its liquid state, and the improvement in solid strength after solidification will be insignificant.
[0018] This invention also provides a pipe jacking construction method based on the above-mentioned phase change material, wherein the phase change material replaces thixotropic mud in the pipe jacking construction, comprising the following steps:
[0019] 1) The phase change material is heated to a certain temperature to completely liquefy the phase change material;
[0020] 2) During the pipe jacking construction, the outer wall of the pipe is heated to a temperature that can at least partially liquefy the phase change material, and all the liquefied phase change material obtained in step 1) is injected into the outer wall of the pipe to play a role in lubrication and drag reduction.
[0021] 3) After the pipe jacking construction is completed, the heating of the pipe is stopped, and the phase change material on the outside of the pipe wall becomes completely solid as the ambient temperature decreases;
[0022] The phase change material is selected from one or more of paraffin, fatty acid-based solid-liquid phase change materials, and fatty alcohol-based solid-liquid phase change materials.
[0023] The preferred embodiment of the phase change material is the same as above.
[0024] More preferably, the phase change material includes two or more phase change materials with different melting points, and during the pipe jacking construction, the outer wall of the pipe is heated to a temperature that can at least partially liquefy the phase change material.
[0025] In a preferred embodiment, in step 2), a heating device (e.g., a hot water pipe) is provided on the outer wall of the top pipe to heat the outer wall of the top pipe to a temperature that can at least partially liquefy the phase change material.
[0026] In another preferred embodiment, in step 2), the jacking pipe is a reinforced concrete jacking pipe. By heating the reinforcing bars in the reinforced concrete jacking pipe, heat is conducted from the reinforcing bars to the outer wall of the jacking pipe in contact with the phase change material, thereby heating the outer wall of the jacking pipe to a temperature that can at least partially liquefy the phase change material. For example, a coil wound around the reinforcing bars can be embedded around the reinforcing bars. When a changing current is passed through the coil, an induced current (i.e., eddy current) is generated inside the reinforcing bars due to electromagnetic induction. The heat generated by the eddy current is used to heat the reinforcing bars.
[0027] The beneficial effects of this invention are at least as follows:
[0028] 1) This invention uses phase change material to replace thixotropic mud in traditional pipe jacking construction. By adjusting the temperature of the outer wall of the pipe jacking, the phase (liquid / solid) of the phase change material is controlled. This not only gives full play to the lubrication and drag reduction effect of traditional thixotropic mud, but also realizes the reinforcement effect of hardenable slurry, thereby solving the problem that thixotropic mud is difficult to push out and replace in traditional construction process.
[0029] 2) This invention preferably uses a composite of multiple phase change materials with different melting points for pipe jacking construction. The degree of melting of the phase change materials can be controlled by adjusting the temperature. Different projects are located in different geological formations, and the resistance to pipe jacking varies. If the project requires a higher degree of lubrication, a higher temperature is used to melt a larger proportion of the phase change materials. Conversely, if a slightly lower degree of lubrication is sufficient, a lower temperature is used to melt a smaller proportion of the phase change materials to save energy. In addition, this invention uses multiple phase change materials with different melting points. If the outer wall of the pipe is heated to a temperature that only the phase change materials with lower melting points can melt during pipe jacking construction, then after all the liquefied phase change materials are injected into the outer wall of the pipe through the grouting holes, the remaining portion of the phase change materials with higher melting points will solidify. This provides a certain strength while ensuring lubrication, thereby limiting the displacement of the pipe from the jacking axis (such as settlement displacement) to a certain extent during jacking construction, and also limiting the infiltration of the liquid phase change materials into the surrounding soil to a certain extent.
[0030] 3) The present invention preferably incorporates 100-185% mineral soil into the phase change material, which can improve its solid strength, reduce the loss of phase change material in the liquid state, and at the same time hardly affect its lubrication and drag reduction effect in the liquid state. Attached Figure Description
[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0032] Figure 1 This is a schematic diagram of pipe jacking based on thixotropic mud; Figure 1 The middle arrow indicates the direction of pipe jacking.
[0033] Figure 2 This is a schematic diagram showing the replacement of thixotropic mud after the pipe jacking construction is completed; Figure 2 The middle arrow indicates the direction of travel of the hardenable slurry.
[0034] Among them, 1-jacking pipe section, 2-thixotropic mud, 3-formation, 4-cement grout.
[0035] Figure 3 This is a schematic diagram of the sand box used for model testing.
[0036] Figure 4 This is a schematic diagram showing the heating wire embedded in a sand box.
[0037] Figure 5A schematic diagram of laying a jacking pipe and filling the jacking pipe with phase change material, wherein (a) is a front view and (b) is a side view.
[0038] Figure 6 The diagram shows a buried pipe jacking, where (a) is a front view and (b) is a side view.
[0039] Figure 7 Figure 1 shows a schematic diagram of the phase change material after cooling, where (a) is the overall view and (b) is a partial view. Detailed Implementation
[0040] The present invention will now be described by way of preferred embodiments. It should be understood by those skilled in the art that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.
[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art, or in accordance with the product manual.
[0042] Example 1
[0043] This embodiment provides a pipe jacking construction method based on phase change materials, including the following steps:
[0044] 1) Heat the paraffin wax to 70°C until it is completely liquefied, and add bentonite equivalent to 100% of the mass of the paraffin wax. During the process of adding bentonite, keep the temperature of the paraffin wax not lower than 70°C.
[0045] 2) During the pipe jacking construction, the outer wall of the reinforced concrete pipe is heated to about 70°C, and the fully liquefied paraffin mixed with bentonite obtained in step 1 is injected into the outer wall of the pipe through the grouting hole to play a role in lubrication and drag reduction.
[0046] 3) After the pipe jacking construction is completed, the heating of the reinforced concrete pipe is stopped. The paraffin cools and hardens to generate strength, so there is no need to replace it with hardenable grout.
[0047] In step 2), the reinforcing bars in the reinforced concrete jacking pipe are heated. The heat is conducted from the reinforcing bars to the outer wall of the jacking pipe in contact with the phase change material, thereby heating the phase change material. Eddy current heating of the reinforcing bars can be used, that is, coils with the reinforcing bars wound around them are embedded in the reinforced concrete jacking pipe. When a changing current is passed through, an induced current (i.e., eddy current) is generated inside the reinforcing bars due to electromagnetic induction. The heat generated by the eddy current can be used to heat the reinforcing bars, and the heat is conducted from the reinforcing bars to the outer wall of the jacking pipe, thereby achieving heating.
[0048] Example 2
[0049] This embodiment provides a pipe jacking construction method based on phase change materials, including the following steps:
[0050] 1) The composite phase change material is heated to about 70°C to liquefy it completely, and bentonite equivalent to 100% of the mass of the composite phase change material is added to it; the composite phase change material contains: paraffin and palmitic acid (i.e., palmitic acid) in a volume ratio of 1:1, wherein the melting point of paraffin is about 55°C and the melting point of palmitic acid is 61~62.5°C.
[0051] 2) During the pipe jacking construction, the outer wall of the reinforced concrete pipe is heated to about 58°C (at this temperature, the liquefaction ratio of the composite phase change material is about 50%), and the completely liquefied composite phase change material mixed with bentonite obtained in step 1 is injected into the outer wall of the pipe through the grouting hole to play a role in lubrication and drag reduction.
[0052] 3) After the pipe jacking construction is completed, the heating of the reinforced concrete pipe is stopped, and the composite phase change material is completely cooled and hardened to generate strength, so there is no need to replace it with hardenable grout.
[0053] Example 2 uses the same method as Example 1 for heating reinforced concrete jacking pipe.
[0054] Comparative Example 1
[0055] Comparative Example 1 provides a pipe jacking construction method based on traditional thixotropic mud, including the following steps:
[0056] 1) During pipe jacking construction, thixotropic mud is injected into the outside of the pipe wall to play a role in lubrication and drag reduction; the thixotropic mud, by weight, includes the following components: bentonite: 10%, sodium carbonate: 0.5%, sodium carboxymethyl cellulose: 0.2%, and water: 89.3%.
[0057] 2) After the pipe jacking construction is completed, the thixotropic mud is replaced with traditional cement grout.
[0058] Test case
[0059] The technical effects of Examples 1-2 were verified through scaled-down model experiments. The specific experimental scheme is as follows:
[0060] (1) The model test adopts Figure 3 The sand box shown is used for this process;
[0061] (2) The temperature of the phase change material is controlled by a heating wire, which is embedded in a sand box, such as... Figure 4 As shown;
[0062] (3) Lay a jacking pipe at the location where the heating wire is buried, and fill the area around the jacking pipe with phase change material, such as... Figure 5 As shown;
[0063] (4) Burying the pipe, such as Figure 6 As shown, turn on the heating wire, and after heating the phase change material to the specified temperature, measure the pipe-soil friction coefficient during pipe jacking.
[0064] (5) Turn off the heating wire and wait for the phase change material to cool down before excavating the jacking pipe. Observe that the phase change material exhibits a certain state. Figure 7 The distribution shows that the phase change material forms a continuous coating layer around the jacking pipe, proving that the phase change material can form a continuous lubricating layer around the jacking pipe when it melts, and can play a reinforcing role after solidification, providing strength to ensure the stability of the jacking pipe structure.
[0065] (6) To quantitatively measure the drag reduction effect of phase change materials, the above processes (1) to (5) were performed using the phase change materials and pipe outer wall temperature conditions involved in Examples 1 and 2, and the corresponding pipe-soil friction coefficients were measured. The results are shown in Table 1 below. For Comparative Example 1, the pipe-soil friction coefficient using traditional thixotropic mud was taken as the lowest value suggested in Reference 1, which was 0.1.
[0066] Table 1. Friction coefficient between pipe and soil
[0067]
[0068] (7) The unit weight of soil is taken as 19 kN / m 3 The frictional resistance under different working conditions when the pipe jacking depth is 10m was calculated according to the calculation method given in Reference 2. The results are shown in Table 2 below.
[0069] Table 2
[0070]
[0071] Note: The unit weight of soil is approximately 19 kN / m³. 3 .
[0072] Specifically, the aforementioned references 1-2 are as follows:
[0073] Reference 1 is: Stein D, Möllers K, Bielecki R. Microtunneling installation and renewal of nonman-size supply and sewage lines by the trenchless construction method. Berlin: Ernst&Sohn, 1989.
[0074] Reference 2 is: Zhang Peng, Tan Lixin, Ma Baosong. Formula for frictional resistance of pipe jacking considering slurry thixotropy and pipe-soil contact characteristics. Chinese Journal of Geotechnical Engineering, 2017, 39 (11): 2043-2049.
[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A pipe jacking construction method based on a phase change material, characterized in that, The phase change material replaces thixotropic mud in pipe jacking construction, including the following steps: 1) The phase change material is heated to a certain temperature to completely liquefy it, and mineral soil is added to it; 2) During the pipe jacking construction, the outer wall of the pipe is heated to a temperature that can at least partially liquefy the phase change material, and all the liquefied phase change material obtained in step 1) is injected into the outer wall of the pipe to play a role in lubrication and drag reduction. 3) After the pipe jacking construction is completed, the heating of the pipe is stopped, and the phase change material on the outside of the pipe wall becomes completely solid as the ambient temperature decreases; The phase change material includes two or more phase change materials with different melting points, selected from two or more of paraffin, fatty acid solid-liquid phase change materials and fatty alcohol solid-liquid phase change materials; The mineral soil is selected from one or more of bentonite, kaolin, and diatomite; the amount of mineral soil added is 100-185% based on the mass of the phase change material.
2. The pipe jacking construction method according to claim 1, characterized in that, The first phase change material has the highest melting point, the second phase change material has a lower melting point than the first phase change material, and so on.
3. The pipe jacking construction method according to claim 2, characterized in that, The melting point of the second phase change material is 5-10°C lower than that of the first phase change material, and so on.