In-situ protection system and construction method for underground pipelines during close-in construction

Abstract

This invention relates to the field of in-situ protection technology for underground pipelines, and more particularly to an in-situ protection system for underground pipelines during close-proximity construction. The system includes: a temporary support trench, installed along the length of the underground pipeline, with the pipeline suspended within it; a buoyancy fluid injected into the temporary support trench to provide buoyancy for the underground pipeline; temporary support units, spaced at intervals along the length of the underground pipeline at the bottom of the temporary support trench, providing temporary support for the underground pipeline during construction or backfilling; and a level regulating unit connected to the temporary support trench to regulate the level of the buoyancy fluid within the trench. This invention utilizes the principle of fluid buoyancy and dynamic level control to provide uniform and flexible support for the pipeline, thereby dynamically isolating the pipeline from soil deformation caused by close-proximity construction. This avoids the stress concentration problem associated with traditional point supports or suspensions due to foundation deformation.

Description

Technical Field

[0001] This invention relates to the field of in-situ protection technology for underground pipelines, and in particular to an in-situ protection system and construction method for underground pipelines during close-proximity construction of adjacent pipelines. Background Technology

[0002] In urban construction, it is often necessary to carry out close-proximity construction such as tunnels and foundation pits near existing underground pipelines (such as water supply, gas, heating, and electricity lines). Due to the importance of the pipeline's service function or the complexity of the surrounding environment, relocation is often difficult, and in-situ protection is the only option. Currently, traditional in-situ protection methods are mainly rigid protection methods, such as suspension protection (suspending pipelines using steel trusses and cables) and support protection (setting up steel supports or concrete piers under the pipeline).

[0003] However, these traditional methods have inherent drawbacks: the protective structure and the pipeline are in rigid contact. When nearby construction causes settlement or uplift of the surrounding soil, the soil serving as the foundation of the protective structure also deforms, leading to displacement of the suspended or supporting structure. Due to the rigid connection, the displacement is directly and forcibly transmitted to the pipeline, which not only fails to provide protection but may also cause the pipeline to rupture and leak due to excessive deformation, or even trigger serious safety accidents such as collapse or explosion.

[0004] Although there are some improvements in the existing technology, such as the construction method and system for automatic settlement compensation of underground pipelines across foundation pits disclosed in patent application number CN202110189121.5, it still relies on complex sensors and precision lifting mechanisms, the system cost is high, and the underground pipelines still face risks when the device itself malfunctions or is damaged. Summary of the Invention

[0005] To address at least one of the aforementioned technical problems, this invention proposes an in-situ protection system and construction method for underground pipelines during close-proximity construction. This addresses the issues of existing rigid protection methods failing to isolate foundation deformation and easily causing pipeline damage, as well as the high cost and insufficient reliability of existing active compensation schemes.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention provides an in-situ protection system for underground pipelines during close-proximity construction, comprising: A temporary support trench is provided along the length of the underground pipeline, and the underground pipeline is suspended in the temporary support trench; A buoyancy fluid is injected into the temporary support tank to provide buoyancy for the underground pipeline; Temporary support units are spaced apart at the bottom of the temporary support trench along the length of the underground pipeline. The temporary support units are used to provide temporary support for the underground pipeline during the construction or backfilling of the temporary support trench. A liquid level regulating unit, connected to the temporary support tank, is used to regulate the liquid level of the floating liquid in the temporary support tank.

[0007] Preferably, the system further includes an auxiliary support unit, which includes floating rings spaced at intervals along the length of the underground pipeline on the outer wall of the underground pipeline and fasteners for fixing the floating rings to the underground pipeline.

[0008] Preferably, the floating ring is a split-type annular airbag or a split-type float.

[0009] Preferably, the longitudinal section of the temporary support groove is trapezoidal.

[0010] Preferably, the temporary support unit includes: A temporary support foundation is fixedly installed at the bottom of the temporary support groove; A temporary support platform is vertically fixed on the upper part of the temporary support foundation, and the upper part of the temporary support platform is provided with a bearing surface to facilitate the placement and restraint of the underground pipeline.

[0011] Preferably, the liquid level regulating unit includes: A level gauge, vertically installed in the temporary support tank, is used to measure the depth of the floatation liquid; The liquid level regulating tank is connected to the temporary support tank through an inlet pipe and an outlet pipe, and an inlet pump and a outlet pump are respectively installed on the inlet pipe and the outlet pipe; A level control box, connected to the level gauge, the inlet pump, and the outlet pump, is used to adjust the level of the floating liquid in the temporary support tank according to the upper limit H1 and the lower limit H2 of the floating liquid level control, so as to regulate the buoyancy force on the underground pipeline.

[0012] Preferably, the temporary support trough is provided with an isolation and leak-proof layer to prevent the floatation fluid from leaking out.

[0013] Preferably, the density of the flocculation fluid is 1~1.7 g / cm³. 3 .

[0014] A second aspect of the present invention provides a construction method for an in-situ protection system for underground pipelines during close-proximity construction as described in the first aspect, comprising the following steps: S1. Before close-in construction, investigate the distribution, shape and size of underground pipelines and assess the impact range of close-in construction, and determine the size and location of temporary support trenches and temporary support units; S2, on both sides of the underground pipeline, temporary support trenches are excavated in a segmented and zoned manner, and temporary support platforms and auxiliary support units are installed according to the design spacing; S3, Lay an isolation and leak-proof layer on the inner wall and bottom of the temporary support tank, conduct a water tightness test, and install a level gauge in the temporary support tank; S4. Excavate or place a prefabricated liquid level regulating tank next to the temporary support tank, lay inlet and outlet pipes between the temporary support tank and the liquid level regulating tank, and install inlet and outlet pumps. Connect the liquid level gauge, inlet pump and outlet pump to the liquid level control box. S5. Prepare the floatation fluid according to the preset floatation fluid density, and pour the floatation fluid into the temporary support tank until the liquid level line reaches the initial liquid level. The initial liquid level is between the upper limit of liquid level control H1 and the lower limit of liquid level control H2. S6, inject a certain amount of floatation fluid into the liquid level regulating tank. During close-contact construction, the liquid level of the floatation fluid in the temporary support tank is controlled by the liquid level regulating unit. S7. After the immediate construction is completed, drain the floating liquid in the temporary support trench, backfill the temporary support trench in layers, and remove the temporary support platform.

[0015] Preferably, step S6 includes the following steps; S61 monitors the level of the floating liquid in the temporary support tank through a level gauge and obtains the monitoring data in real time through the level control box; S62, when the level of the floating liquid in the temporary support tank is higher than the upper limit of the liquid level control H1, the liquid level control box starts the drain pump and discharges the floating liquid into the liquid level regulating tank through the drain pipeline until the level of the floating liquid in the temporary support tank is restored to the initial level. S63, when the level of the floating liquid in the temporary support tank is lower than the lower limit of the liquid level control H2, the liquid level control box starts the inlet pump and draws the floating liquid in the liquid level adjustment tank into the temporary support tank through the inlet pipeline until the level of the floating liquid in the temporary support tank is restored to the initial level.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention employs a temporary support trench, immersing underground pipelines in a buoyancy solution within the trench. The buoyancy of this solution provides flexible support to the pipelines, ensuring that the net force on the pipelines is solely dependent on the magnitude of the buoyancy, unaffected by foundation deformation. This effectively cuts off the path of foundation deformation transmitted to the pipelines through the protective structure during near-construction, thus achieving active isolation of pipeline deformation. Simultaneously, the buoyancy provides continuous and uniform force along the pipeline to the submerged portion, avoiding stress concentration issues inherent in traditional point supports or suspension systems.

[0017] By dynamically adjusting the level of the buoyancy fluid through the level adjustment unit, the volume of the underground pipeline submerged in the buoyancy fluid can be adjusted in a timely manner, thereby adjusting the buoyancy of the underground pipeline in real time. This avoids changes in the buoyancy of the underground pipeline caused by changes in the shape of the temporary support trench due to foundation deformation (such as subsidence or uplift) during close construction, and ensures that the underground pipeline is in a relatively stable stress state. Attached Figure Description

[0018] Figure 1 A top view of an in-situ protection system for underground pipelines during close-proximity construction of nearby pipelines; Figure 2 for Figure 1 Sectional view along axis AA; Figure 3 for Figure 2 Sectional view along the BB direction; Figure 4 A flowchart of a construction method for an in-situ protection system for underground pipelines during close-in construction of nearby pipelines; In the diagram: 10. Temporary support trench; 20. Underground pipeline; 30. Temporary support unit; 301. Temporary support foundation; 302. Temporary platform; 40. Liquid level regulating unit; 401. Liquid level gauge; 402. Liquid level regulating tank; 403. Liquid inlet pipeline; 404. Liquid outlet pipeline; 405. Liquid inlet pump; 406. Liquid outlet pump; 407. Liquid level control box; 50. Auxiliary support unit; 60. Isolation and leak-proof layer. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments of the present invention.

[0020] Example 1 Please refer to Figures 1-3 As shown, an in-situ protection system for underground pipeline 20 during close-proximity construction includes: The temporary support trench 10 is set along the length of the underground pipeline 20, and the underground pipeline 20 is suspended in the temporary support trench 10. The buoyancy fluid is injected into the temporary support tank 10 to provide buoyancy for the underground pipeline 20; Temporary support units 30 are spaced out at the bottom of temporary support trench 10 along the length of underground pipeline 20. Temporary support units 30 are used to provide temporary support for underground pipeline 20 during construction or backfilling of temporary support trench 10. The liquid level adjustment unit 40 is connected to the temporary support tank 10 and is used to adjust the liquid level of the floating liquid in the temporary support tank 10.

[0021] In this embodiment, a temporary support tank 10 is set up, and the underground pipeline 20 is immersed in the buoyancy liquid within the temporary support tank 10. The buoyancy of the buoyancy liquid provides flexible support to the underground pipeline 20, ensuring that the resultant force on the underground pipeline 20 is only related to the magnitude of the buoyancy force and is unaffected by foundation deformation. This cuts off the path of foundation deformation transmitted to the underground pipeline 20 through the protective structure during close-proximity construction, thus achieving active isolation of the underground pipeline 20 from deformation. Simultaneously, the buoyancy provides a continuous and uniform force along the underground pipeline 20 to the portion submerged in the buoyancy liquid, avoiding the stress concentration problem present in traditional point supports or suspensions.

[0022] In addition, by dynamically adjusting the level of the buoyancy fluid through the level adjustment unit 40, the volume of the underground pipeline 20 submerged in the buoyancy fluid can be adjusted in a timely manner, thereby adjusting the buoyancy force on the underground pipeline 20 in real time. This avoids changes in the buoyancy force of the underground pipeline 20 caused by changes in the shape of the temporary support trench 10 due to foundation deformation (such as subsidence or uplift) during close construction, and ensures that the underground pipeline 20 is in a relatively stable state under stress.

[0023] In this embodiment, the temporary support 302 provides reliable temporary support for the underground pipeline 20 during the excavation or backfilling of the temporary support trench 10, thus avoiding the problem of settlement and deformation of the underground pipeline 20 during construction.

[0024] It should be noted that the longitudinal section of the temporary support trench 10 in this embodiment is trapezoidal. Obviously, the longitudinal section shape of the temporary support trench 10 can be selected according to the underground pipeline 20 and the construction environment, and this application does not limit it here.

[0025] In this embodiment, the function of the buoyancy fluid is to provide continuous buoyancy for the underground pipeline 20 during the construction period. Therefore, the buoyancy fluid needs to avoid significant settlement, stratification or segregation during the construction period, maintain a relatively uniform density, and have low permeability. In conjunction with the isolation and leak-proof layer 60 described below, the loss of buoyancy fluid seeping into the soil is reduced.

[0026] The density of the floatation fluid can also be selected based on the volume and material of the pipeline. In this embodiment, the density of the floatation fluid is 1~1.7 g / cm³. 3 .

[0027] Specifically, in this embodiment, the flocculation fluid consists of water, sodium-based bentonite, and a fluid loss reducing agent (such as polyanionic cellulose PAC). Bentonite powder (typically 5%–10% of the water weight) is slowly added to the water under high-speed stirring, allowing it to fully hydrate and form a colloid. Subsequently, a small amount of thickener and fluid loss reducing agent are added to adjust the rheological properties and filtration loss. This bentonite-based mud system exhibits good suspension stability (thixotropy) and impermeability, is suitable for most soil conditions, is low-cost, and environmentally friendly.

[0028] Of course, depending on the material of the underground pipeline and the geological conditions, the buoyancy solution can also be a high-density salt solution (such as calcium chloride or magnesium chloride solution).

[0029] Understandably, in practice, when the protected underground pipeline 20 is a heavy pipeline (such as a large-diameter steel pipe or cast iron pipe) or transports a high-density medium, the total weight per unit length may be large. In this case, relying solely on adjusting the density of the buoyancy fluid to provide sufficient buoyancy may present the following problems: preparing a highly concentrated and stable buoyancy fluid is technically difficult, costly, and may be corrosive; excessively high density will lead to excessively high viscosity of the buoyancy fluid, severely affecting the normal operation of the level regulating unit 40.

[0030] Based on the above factors, in a preferred embodiment, the system further includes an auxiliary support unit 50, which includes floating rings spaced along the length of the underground pipeline 20 on the outer wall of the underground pipeline 20 and fasteners for fixing the floating rings to the underground pipeline 20.

[0031] Specifically, by placing a floating ring with a lower density and a relatively larger volume around the underground pipeline 20, the overall buoyancy of the underground pipeline 20 is effectively improved without changing the original submerged volume of the underground pipeline 20 and within a relatively optimal range of buoyancy fluid density.

[0032] It should be noted that, for the already laid underground pipeline 20, in order to facilitate the installation of the floating ring, the floating ring in this embodiment is a split-type annular airbag or a split-type float.

[0033] Specifically, taking a split-type annular airbag as an example, it can be made of flexible, airtight materials (such as high-strength coated fabrics or rubber composites) with an internal cavity. It employs two semi-annular airbag flaps, with rigid flanges containing bolt holes pre-embedded or vulcanized at the mating edges of the semi-annular airbags. During installation, a rubber gasket is sandwiched between the two flanges, and bolts are used to tighten the connection, forming a high-strength, highly airtight connection. Obviously, the two semi-annular airbag flaps can also be connected using other mechanisms. For example, an industrial-grade airtight and waterproof zipper can be used at the mating edges of the airbag flaps.

[0034] Meanwhile, in order to facilitate flexible adjustment of the volume of the annular airbag in the buoyancy fluid, the annular airbag in this embodiment is provided with an inflation port, which can be used to adjust the volume and buoyancy of the airbag by filling it with air or inert gas.

[0035] Please refer to Figure 1 and Figure 2 As shown, in a preferred embodiment, the temporary support unit 30 includes: Temporary support foundation 301 is fixedly installed at the bottom of temporary support groove 10; The temporary support platform 302 is vertically fixed on the upper part of the temporary support foundation 301. The upper part of the temporary support platform 302 is provided with a bearing surface to facilitate the placement and restraint of the underground pipeline 20.

[0036] In this embodiment, the concentrated load from the temporary support foundation 301 can be diffused and evenly transferred to the bottom of the temporary support trench 10 over a larger area, significantly reducing the contact stress at the bottom of the temporary support trench 10 and preventing local soil from being pressed in due to excessive stress, which could lead to settlement.

[0037] Meanwhile, the bearing surface of the temporary support 302 can be designed to match the shape of the underground pipeline 20. For example, if the underground pipeline 20 is cylindrical, the bearing surface can be arc-shaped. The arc-shaped surface applies lateral constraints to the underground pipeline 20, preventing lateral displacement of the underground pipeline 20. In this embodiment, the temporary support unit 30 can be made of steel, which facilitates assembly and disassembly.

[0038] Please refer to Figure 2 and Figure 3 As shown, in a preferred embodiment, the liquid level regulating unit 40 includes: The level gauge 401 is vertically installed in the temporary support tank 10 and is used to measure the depth of the float liquid.

[0039] It should be noted that the level gauge 401 in this embodiment can be an electronic level gauge. Specifically, an electronic level gauge is essentially an array-type level sensor or a capacitive / resistive continuous level sensor. The typical working principle is as follows: a vertically mounted probe (or a cable with a series of equally spaced sensing points) is immersed in the liquid, forming a capacitance or conductive circuit between the liquid and the sensing electrodes, thereby detecting the liquid level. Simultaneously, the probe is sealed along its entire length with a stainless steel outer casing, thus effectively preventing the adhesion of skid plate fluid, salt spray corrosion, and moisture intrusion.

[0040] Because electronic level gauges use direct contact measurement, compared to ultrasonic level gauges and float level gauges, they avoid interference from environmental factors such as foam and optical fibers within the temporary support tank 10, ensuring the accuracy of level measurement. Furthermore, the 4-20mA analog or digital signal continuously measuring the level can be directly connected to the analog input module of the level control box 407 (PLC or dedicated controller) without requiring additional signal conversion.

[0041] The liquid level regulating tank 402 is connected to the temporary support tank 10 through the liquid inlet pipe 403 and the liquid outlet pipe 404. The liquid inlet pipe 403 and the liquid outlet pipe 404 are respectively equipped with a liquid inlet pump 405 and a liquid outlet pump 406.

[0042] Understandably, the use of bidirectional independent inlet pipes 403 and outlet pipes 404 allows the system to quickly replenish and drain liquid as needed, avoiding problems such as valve switching failures and backflow that exist with single pipes and reversible pumps, thus improving the system's redundancy.

[0043] The liquid level control box 407 is connected to the liquid level gauge 401, the inlet pump 405 and the outlet pump 406. It is used to adjust the liquid level of the floating liquid in the temporary support tank 10 according to the upper limit H1 and the lower limit H2 of the floating liquid, so as to regulate the buoyancy force on the underground pipeline 20.

[0044] It should be noted that the method for determining the upper limit H1 and lower limit H2 of the liquid level control in this embodiment is as follows: The volume of the pipeline located in the temporary support trench is V0; the volume of the underground pipeline located in the floatation fluid is V. In the temporary support tank, when the level of the floating liquid is at the upper control limit H1, the underground pipeline is submerged in a liquid volume of V1. When the liquid level is at the lower control limit H2, the volume of the underground pipeline submerged in the float liquid is V2. Let the self-weight of the pipeline be M1, the mass of the fluid in the underground pipeline be M2, and the density of the buoyancy fluid be ρ. Therefore: The total buoyancy force on the underground pipeline is: F = ρ V, Total weight of underground pipelines: G = M1 + M2 For common underground pipelines made of polymer materials, to meet protection requirements, it can be ensured that F > G, and: (1) When the liquid level is at the upper control limit H1: F1=ρ V1 = G(1 + k).

[0045] At this moment, the underground pipeline is subjected to a resultant force of Gk, which is evenly distributed along the length of the pipeline and is directed vertically upward.

[0046] (2) When the liquid level is at the lower control limit H2: F2=ρ V2 = G(1-k).

[0047] At this moment, the underground pipeline is subjected to a resultant force of They are evenly distributed along the length of the underground pipeline, and the direction is vertically downward.

[0048] In the above formula, k is the safety factor, which is calculated based on the allowable stress σ of the pipe material for a thin-walled circular pipe with a length of L in the underground pipeline.

[0049] When the liquid level is at the upper limit of the liquid level control H1: M is the bending moment experienced by the underground pipeline located at the midpoint of the temporary support trench: M = 1 / 12 (F1 - G) L = 1 / 12kGL.

[0050] If the allowable bending stress of the pipe wall is σ, and the section modulus of the underground pipeline is W, then: σ = M / W, from which we can derive: k = 12σW / (GL).

[0051] V1 and V2 can be determined based on the calculated safety factor k.

[0052] Based on the relative geometric positions of the temporary support tank and the pipeline, a function V=f(H) is established to correspond to the liquid level height H and the pipeline immersion volume V. By solving the equations f(H1)=V1 and f(H2)=V2, the upper limit H1 and lower limit H2 of the liquid level control system of the automatic liquid level control system can be obtained.

[0053] It should be noted that the specific form of the function f(H) depends on the cross-sectional shape of the pipe (circular, rectangular, etc.) and its installation position in the channel, and can be determined through geometric calculations. For example, for common circular pipes, the area of ​​the arc can be calculated using the formula for the area of ​​the arc.

[0054] Please refer to Figure 2 As shown, in a preferred embodiment, the temporary support trough 10 is provided with an isolation and leak-proof layer 60 to prevent leakage of the buoyancy fluid. Specifically, the isolation and leak-proof layer 60 can be made of polymer waterproof membrane, fully covering the bottom plate and side walls of the temporary support trough 10. Sufficient overlap width (typically ≥10cm) is required between the membrane rolls. For thermoplastic membranes such as HDPE, a double-track hot-melt welding machine can be used to weld two parallel cavity welds, and pressure testing can be performed to ensure the welds are sealed. For materials such as PVC, hot air welding or special solvent welding can be used. At the location where the underground pipeline 20 passes through the leak-proof layer, a special pipe sealing sleeve or a "flared mouth" can be fabricated on-site and double-sealed (e.g., internal shrink wrap and external waterproof sealant) to ensure the sealing of this vulnerable point.

[0055] Example 2 Please refer to Figure 4 As shown, a construction method for an in-situ protection system for underground pipelines during close-proximity construction includes the following steps: S1. Before the close-in construction, investigate the distribution, shape and size of the underground pipeline 20 and assess the impact range of the close-in construction, and determine the size and location of the temporary support trench 10 and the temporary support unit 30.

[0056] Specifically, the distribution location, shape, and size of underground pipeline 20 can be accurately determined on-site by combining geophysical exploration (such as ground-penetrating radar and pipeline detectors) with necessary pit exploration (artificial pit exploration). The actual trajectory, interface location, pipe diameter, wall thickness, material, and current working status (pressure and flow rate) of the pipeline in three-dimensional space can be precisely calibrated.

[0057] The impact range of near-construction refers to the range of ground displacement that may be caused by near-construction (such as a tunnel underpass). Specifically, it is necessary to make scientific predictions based on engineering geological conditions, construction methods (such as shield tunneling and mining methods), tunnel dimensions and burial depth, etc., using empirical formulas (such as Peck's formula), numerical simulations or analogous engineering data, to determine the width of the surface settlement trough, the maximum settlement, and the boundaries of the main impact areas.

[0058] S2, on both sides of the underground pipeline 20, temporary support trenches 10 are excavated in a segmented and zoned manner, and temporary support platforms 302 and auxiliary support units 50 are installed according to the design spacing.

[0059] Specifically, "segmentation" refers to dividing the long underground pipeline's protection area into several independent working sections (such as each section being 6-12 meters long) and constructing them section by section; "zoning" refers to further dividing the excavation face into small working areas on the left and right sides and upper and lower layers within each working section.

[0060] Meanwhile, once the soil beneath the underground pipeline 20 is excavated to the design depth, the weight of this section of pipeline can be supported by the temporary support foundation 301 and the temporary pier 302.

[0061] S3, lay an isolation and leak-proof layer 60 on the inner wall and bottom of the temporary support tank 10, conduct a water tightness test, and install a level gauge 401 in the temporary support tank 10.

[0062] Specifically, after the isolation and leak-proof layer is laid, a special testing needle can be inserted into the cavity of the double-rail weld, and air can be injected to a specified pressure (e.g., 0.2 MPa). The pressure is then observed to ensure it remains stable within a specified time. Next, a small amount of clean water is injected into the tank to a certain height, and the rate of water level drop is observed to determine if there are any leaks in the isolation and leak-proof layer.

[0063] S4. Excavate or place a prefabricated liquid level regulating tank 402 next to the temporary support tank 10, lay the liquid inlet pipe 403 and the liquid outlet pipe 404 between the temporary support tank 10 and the liquid level regulating tank 402, and install the liquid inlet pump 405 and the liquid outlet pump. Connect the liquid level gauge 401, the liquid inlet pump 405 and the liquid outlet pump to the liquid level control box 407.

[0064] S5. Prepare the floatation fluid according to the preset floatation fluid density, and pour the floatation fluid into the temporary support tank 10 until the liquid level line reaches the initial liquid level, which is between the upper limit of liquid level control H1 and the lower limit of liquid level control H2.

[0065] It should be noted that the initial liquid level in this embodiment should meet the following conditions: the buoyancy force on the underground pipeline 20 (including the buoyancy force of the underground pipeline 20 itself and the buoyancy force of the float ring) should be equal to or close to the sum of the weight of the underground pipeline 20 itself and the weight of the medium inside the underground pipeline 20. At this time, the total resultant force of the underground pipeline 20 is close to zero. At this time, the underground pipeline 20 is in a relatively stable state of suspension equilibrium of ground stress.

[0066] S6. A certain amount of floatation fluid is injected into the liquid level regulating tank 402. During close-contact construction, the liquid level of the floatation fluid in the temporary support tank 10 is controlled by the liquid level regulating unit 40.

[0067] Specifically, in this embodiment, S6 includes the following steps: S61, the level of the floating liquid in the temporary support tank 10 is monitored by the level gauge 401, and the level control box 407 acquires the monitoring data in real time; S62, when the level of the floating liquid in the temporary support tank 10 is higher than the upper limit of the liquid level control H1, the liquid level control box 407 starts the drain pump 406 to discharge the floating liquid into the liquid level regulating tank 402 through the drain pipeline until the level of the floating liquid in the temporary support tank 10 returns to the initial level. S63, when the level of the floating liquid in the temporary support tank 10 is lower than the lower limit of the liquid level control H2, the liquid level control box 407 starts the inlet pump 405, and draws the floating liquid in the liquid level adjustment tank 402 into the temporary support tank 10 through the inlet pipeline 403 until the level of the floating liquid in the temporary support tank 10 is restored to the initial level.

[0068] S7. After the immediate construction is completed, drain the slurry in the temporary support trough 10, backfill the temporary support trough 10 in layers, and remove the temporary support platform 302.

[0069] The underground pipeline 20 in-situ protection system and construction method provided by the present invention utilize the principle of fluid buoyancy and provide uniform and flexible support for the pipeline through dynamic liquid level control, thereby dynamically isolating the pipeline from soil deformation caused by nearby construction, fundamentally avoiding damage to the pipeline due to foundation deformation.

[0070] The above description is a specific implementation of the embodiments of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. An in-situ protection system for underground pipelines during close-proximity construction, characterized in that, include: A temporary support trench (10) is provided along the length of the underground pipeline (20), and the underground pipeline (20) is suspended in the temporary support trench (10); A buoyancy fluid is injected into the temporary support tank (10) to provide buoyancy for the underground pipeline (20); Temporary support units (30) are spaced apart at the bottom of the temporary support trench (10) along the length of the underground pipeline (20). The temporary support units (30) provide temporary support for the underground pipeline (20) during the construction or backfilling of the temporary support trench (10). The liquid level adjustment unit (40) is connected to the temporary support tank (10) and is used to adjust the liquid level of the floating liquid in the temporary support tank (10).

2. The in-situ protection system for underground pipelines during close-proximity construction as described in claim 1, characterized in that, The system also includes an auxiliary support unit (50), which includes floating rings spaced along the length of the underground pipeline (20) on the outer wall of the underground pipeline (20) and a fixing member for fixing the floating rings to the underground pipeline (20).

3. The in-situ protection system for underground pipelines during close-proximity construction according to claim 2, characterized in that, The floating ring is a split-type annular airbag or a split-type float.

4. The in-situ protection system for underground pipelines during close-proximity construction according to claim 3, characterized in that, The longitudinal section of the temporary support groove (10) is trapezoidal.

5. The in-situ protection system for underground pipelines during close-proximity construction according to claim 4, characterized in that, The temporary support unit (30) includes: A temporary support base (301) is fixedly installed at the bottom of the temporary support groove (10); A temporary support platform (302) is vertically fixed on the upper part of the temporary support foundation (301), and the upper part of the temporary support platform (302) is provided with a bearing surface that facilitates the placement and restraint of the underground pipeline (20).

6. The in-situ protection system for underground pipelines during close-proximity construction according to claim 5, characterized in that, The liquid level regulating unit (40) includes: A level gauge (401) is vertically installed in the temporary support tank (10) to measure the depth of the float liquid; The liquid level regulating tank (402) is connected to the temporary support tank (10) through the liquid inlet pipe (403) and the liquid outlet pipe (404). The liquid inlet pipe (403) and the liquid outlet pipe (404) are respectively equipped with a liquid inlet pump (405) and a liquid outlet pump (406). The liquid level control box (407) is connected to the liquid level gauge (401), the inlet pump (405) and the outlet pump (406) to adjust the liquid level of the floating liquid in the temporary support tank (10) according to the upper limit H1 and the lower limit H2 of the floating liquid, so as to adjust the buoyancy force on the underground pipeline (20).

7. The in-situ protection system for underground pipelines during close-proximity construction according to claim 6, characterized in that, The temporary support tank (10) is provided with an isolation and leak-proof layer (60) to prevent the floatation fluid from leaking.

8. The in-situ protection system for underground pipelines during close-proximity construction according to claim 7, characterized in that, The density of the flocculation fluid is 1–1.7 g / cm³. 3 .

9. A construction method for an in-situ protection system for underground pipelines during proximity construction as described in claim 8, characterized in that, Includes the following steps: S1. Before the close-in construction, investigate the distribution, shape and size of the underground pipeline (20) and assess the impact range of the close-in construction, and determine the size and location of the temporary support trench (10) and the temporary support unit (30); S2, on both sides of the underground pipeline (20), temporary support trenches (10) are excavated in a segmented and zoned manner, and temporary support platforms (302) and auxiliary support units (50) are installed according to the design spacing. S3, lay an isolation and leak-proof layer (60) on the inner wall and bottom of the temporary support tank (10), conduct a water tightness test, and install a level gauge (401) in the temporary support tank (10). S4. Excavate or place a prefabricated liquid level regulating tank (402) next to the temporary support tank (10), lay the liquid inlet pipe (403) and liquid outlet pipe (404) between the temporary support tank (10) and the liquid level regulating tank (402), and install the liquid inlet pump (405) and the liquid outlet pump. Connect the liquid level gauge (401), the liquid inlet pump (405) and the liquid outlet pump to the liquid level control box (407). S5. Prepare the floatation fluid according to the preset floatation fluid density, and inject the floatation fluid into the temporary support tank (10) until the liquid level line reaches the initial liquid level. The initial liquid level is between the upper limit of liquid level control H1 and the lower limit of liquid level control H2. S6, inject a certain amount of floatation liquid into the liquid level regulating tank (402), and control the liquid level of the floatation liquid in the temporary support tank (10) through the liquid level regulating unit (40) during close construction; S7. After the immediate construction is completed, drain the floating liquid in the temporary support trench (10), backfill the temporary support trench (10) in layers, and remove the temporary support platform (302).

10. The in-situ protection system for underground pipelines during close-proximity construction according to claim 9, characterized in that, S6 includes the following steps; S61, the level of the floating liquid in the temporary support tank (10) is monitored by the level gauge (401), and the monitoring data is obtained in real time by the level control box (407); S62, when the level of the floating liquid in the temporary support tank (10) is higher than the upper limit of the liquid level control H1, the liquid level control box (407) starts the drain pump (406) and discharges the floating liquid into the liquid level regulating tank (402) through the drain pipeline until the level of the floating liquid in the temporary support tank (10) returns to the initial level. S63, when the level of the floating liquid in the temporary support tank (10) is lower than the lower limit of the liquid level control H2, the liquid level control box (407) starts the inlet pump (405) and draws the floating liquid in the liquid level adjustment tank (402) into the temporary support tank (10) through the inlet pipeline (403) until the level of the floating liquid in the temporary support tank (10) is restored to the initial level.

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