Tunnel peripheral soil body seepage prevention and reinforcement method

Abstract

The application provides a tunnel peripheral soil body anti-seepage reinforcement method, and belongs to the technical field of grouting materials and geotechnical reinforcement. The tunnel peripheral soil body anti-seepage reinforcement method comprises the following steps: (1) performing geological exploration on the tunnel peripheral soil body, and identifying and dividing different grades of seepage weak areas; (2) arranging an anode electrode, an auxiliary electrode and a cathode electrode in a staggered manner along the tunnel ring through a secondary grouting hole; (3) arranging mutually independent calcium source pipes and carbon source pipes along the tunnel axis, wherein the calcium source pipes and the carbon source pipes are provided with openings; (4) releasing calcium source solution and carbon source solution into the tunnel peripheral soil body through the calcium source pipes and the carbon source pipes, and simultaneously applying a control voltage and a current to the anode electrode, the auxiliary electrode and the cathode electrode, so as to drive the ions in the calcium source solution and the carbon source solution to migrate directionally under the action of an electric field and react to generate cementing materials in the seepage weak areas, thereby achieving soil body reinforcement and anti-seepage; and (5) detecting the reinforcement effect.

Description

Technical Field

[0001] This application belongs to the field of grouting materials and soil reinforcement technology, specifically relating to a method for seepage prevention and reinforcement of soil around a tunnel. Background Technology

[0002] The geological conditions of the mountain tunnel traversing the area are complex and varied, with problems such as uneven soil, differences in hydrological conditions and soil and rock layer distribution. Due to the loose soil structure, softening upon contact with water, and the high ground stress that easily induces collapse, the tunnel excavation process is prone to causing stress release in the surrounding soil and triggering soil instability. Therefore, seepage prevention and reinforcement measures must be taken for the soil around the tunnel during the tunnel excavation stage and after the completion of construction.

[0003] Currently, commonly used tunnel reinforcement techniques include grouting, jet grouting, and lining with waterproofing layers. However, these techniques generally suffer from problems such as easy material aging, chemical pollution risks, and poor geological adaptability. To ensure tunnel construction safety and improve project quality, it is urgent to adopt advanced and environmentally friendly soil reinforcement and support technologies tailored to local conditions. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a method for seepage prevention and reinforcement of the soil surrounding a tunnel, aiming to at least partially solve the above-mentioned technical problems. The specific technical solution provided by this application is as follows.

[0005] This application provides a method for seepage prevention and reinforcement of the soil surrounding a tunnel, which includes the following steps:

[0006] Step (1): Perform three-dimensional scanning modeling of the tunnel lining and secondary grouting holes to obtain three-dimensional information of the secondary grouting holes, conduct geological exploration of the soil around the tunnel, and identify and classify different levels of weak permeability areas.

[0007] Step (2): Through the secondary grouting holes, the anode electrode, auxiliary electrode and cathode electrode are arranged in an alternating manner along the tunnel circumference;

[0008] Step (3): Lay out independent calcium source pipes and carbon source pipes along the tunnel axis, wherein the calcium source pipes and carbon source pipes are provided with openings;

[0009] Step (4): Calcium source solution and carbon source solution are released into the soil outside the tunnel through calcium source pipe and carbon source pipe. At the same time, control voltage and current are applied to the anode electrode, auxiliary electrode and cathode electrode to drive the ions in the calcium source solution and carbon source solution to migrate in a direction under the action of electric field and react to generate cement in the weak permeability area, so as to achieve soil reinforcement and seepage prevention.

[0010] Step (5): Check the reinforcement effect, remove the electrodes, calcium source tube and carbon source tube, and seal the secondary grouting hole.

[0011] In some embodiments, areas with poor permeability are classified into slightly poor, moderately poor, and severely poor areas according to their severity. A slightly poor area is a region with an abnormal permeability coefficient k but without a continuous distribution; a moderately poor area is a region with an abnormal permeability coefficient k forming a continuous abnormal band; and a severely poor area is a region with a permeability coefficient k reaching or exceeding 1 × 10⁻⁶. -4 m / s, or areas where obvious seepage channels or large-scale loose structures have been formed; where the permeability coefficient k is obtained through indoor permeability tests or borehole pressure tests.

[0012] In some embodiments, arranging the anode electrode, auxiliary electrode, and cathode electrode in an alternating manner along the tunnel circumference includes: repeating the arrangement of the anode electrode, auxiliary electrode, and cathode electrode in the order of the tunnel circumference, such that at least one auxiliary electrode is provided between any adjacent anode electrode and cathode electrode.

[0013] In some embodiments, the calcium source pipe and carbon source pipe are arranged independently along the tunnel axis, wherein the calcium source pipe and carbon source pipe are provided with openings, including: the calcium source pipe and carbon source pipe are arranged independently along the tunnel axis, wherein the calcium source pipe is arranged between the anode electrode and the auxiliary electrode, and the carbon source pipe is arranged between the auxiliary electrode and the cathode electrode, and the calcium source pipe and carbon source pipe are provided with openings on the side facing the adjacent auxiliary electrode.

[0014] In some embodiments, the opening on the side of the calcium source tube and carbon source tube facing the adjacent auxiliary electrode includes: the calcium source tube and carbon source tube having an opening in the effective liquid release section corresponding to the auxiliary electrode, wherein the effective liquid release section is a specific functional section on the side of the calcium source tube and carbon source tube facing the auxiliary electrode, the length of the effective liquid release section is 0.6m-1.0m, and the center position of the effective liquid release section corresponds to the auxiliary electrode, and the remaining sections of the calcium source tube and carbon source tube are fully enclosed structures.

[0015] In some embodiments, the aperture of the opening is 0.6mm-1.2mm; the distance between adjacent openings along the tunnel axial direction is 20mm-40mm; and the angle range of the opening is ≤120° along the circumferential direction of the calcium source pipe or carbon source pipe.

[0016] In some embodiments, drainage and venting hoses are provided in parallel in the secondary grouting holes where a cathode electrode and an auxiliary electrode under negative bias are installed, so as to discharge water and gas generated during the electrolysis process.

[0017] In some embodiments, the calcium source solution is a mixed aqueous solution comprising a water-soluble calcium salt and a nucleation regulator; the carbon source solution is an aqueous solution comprising a water-soluble carbonate.

[0018] In some embodiments, the concentration of water-soluble calcium salt in the calcium source solution is 0.6 mol / L-1.5 mol / L; the concentration of nucleating regulator in the calcium source solution is 0.5 g / L-10 g / L; and the concentration of water-soluble carbonate in the carbon source solution is 0.6 mol / L-1.5 mol / L.

[0019] In some embodiments, the water-soluble calcium salt includes calcium chloride; the nucleation regulator includes at least one of carboxymethyl chitosan, L-aspartic acid, and boric acid; and the water-soluble carbonate includes sodium carbonate.

[0020] In some embodiments, the release rates of the carbon source solution and calcium source solution in the calcium source tube and carbon source tube are determined according to the severity of the permeability-deficient area: in a slightly deficient area, the release rate of the carbon source solution and calcium source solution is 0.1 mL / min-0.2 mL / min, and the release time lasts for 4 h-6 h; in a moderately deficient area, the release rate of the carbon source solution and calcium source solution is 0.3 mL / min-0.4 mL / min, and the release time lasts for 6 h-8 h; in a severely deficient area, the release rate of the carbon source solution and calcium source solution is 0.4 mL / min-0.5 mL / min, and the release time lasts for 8 h-10 h.

[0021] In this embodiment, the tunnel perimeter soil seepage prevention and reinforcement method first identifies and divides different levels of seepage-prone areas through three-dimensional scanning modeling combined with geological exploration. Electrodes are then deployed based on secondary grouting holes, and independent calcium source pipes and carbon source pipes with openings are laid along the axial direction, eliminating the need for additional openings and significantly reducing the disturbance to the tunnel and surrounding soil during construction. By applying an electric field to drive the calcium and carbon source ions to migrate directionally to the seepage-prone areas to react and generate cement, targeted soil reinforcement and seepage prevention are achieved, with precise and controllable reinforcement effects. After construction is completed, the relevant electrodes and pipes are removed and the grouting holes are sealed to ensure the integrity of the tunnel structure, effectively improve the mechanical properties and seepage resistance of the soil surrounding the tunnel, and enhance the construction safety and long-term stability of the soil. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the method for seepage prevention and reinforcement of the soil surrounding the tunnel in the embodiments of this application;

[0023] Figure 2 This is a schematic diagram of the circumferential cross-section of the seepage prevention and reinforcement construction process of the soil surrounding the tunnel in this embodiment of the application.

[0024] Figure 3 This is a three-dimensional cross-sectional schematic diagram of the seepage prevention and reinforcement construction process of the soil surrounding the tunnel in the embodiments of this application;

[0025] Figure 4 This is a lateral cross-sectional schematic diagram of the seepage prevention and reinforcement construction process of the soil surrounding the tunnel in the embodiments of this application.

[0026] In the above figures, the reference numerals are as follows:

[0027] 1. Soil surrounding the tunnel; 2. Cathode electrode; 3. Auxiliary electrode; 4. Anode electrode; 5. Calcium source pipe; 6. Carbon source pipe; 7. Tunnel lining; 8. Battery; 9. Control system; 10. Drainage and exhaust hose. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0029] Biomimetic-Chemically Induced Carbonate Precipitation (BCICP) is based on the biomimetic mineralization principle of calcium carbonate. It directly regulates the metathesis reaction between calcium chloride and sodium carbonate between soil particles by adding an external regulator. The resulting calcium carbonate crystals can fill soil pores and cement soil particles, thereby improving the mechanical and permeability properties of the soil.

[0030] As a soil reinforcement technology, BCICP does not rely on microorganisms compared to microbial induced carbonate precipitation technology. It has the advantages of being green and environmentally friendly, pollution-free (the biomimetic nucleation regulator used has good biocompatibility and no harmful byproducts during the reaction process), convenient to operate, minimal disturbance (the cementing liquid is water-soluble and has low viscosity, allowing it to flow freely in the soil), high efficiency, high strength (rapid reaction and short cycle, resulting in high soil strength after reinforcement; the unconfined compressive strength (UCS) of soil samples can reach 12 MPa under surface spraying process), good stability, and low cost (the materials used are common industrial products or natural substances, resulting in lower costs).

[0031] Meanwhile, electroosmosis is one of the effective ways to accelerate soil drainage and consolidation and improve the bearing capacity of soft soil foundations. Its advantage is that it can get rid of the limitation of soil particle size and drive water in the soil to migrate and accumulate from the anode to the cathode, thereby consolidating the soil. However, electroosmosis has the disadvantage that the consolidation effect is limited to the anode area and the soil moisture content in the cathode area is still very high, which limits its further application.

[0032] Based on this, this application provides a method for seepage prevention and reinforcement of soil around a tunnel. By using biomimetic mineralization-induced calcium carbonate precipitation technology, combined with an improved electroosmosis method by adding an electrolyte solution, the metathesis reaction of calcium chloride and sodium carbonate is controlled to generate calcium carbonate crystals, which fill the soil pores and cement the soil particles, thereby achieving seepage prevention and reinforcement of the soil around the tunnel.

[0033] Figure 1 This is a flowchart illustrating the method for seepage prevention and reinforcement of the soil surrounding the tunnel in the embodiments of this application; Figure 2This is a schematic diagram of the circumferential cross-section of the seepage prevention and reinforcement construction process of the soil surrounding the tunnel in this embodiment of the application. Figure 3 This is a three-dimensional cross-sectional schematic diagram of the seepage prevention and reinforcement construction process of the soil surrounding the tunnel in the embodiments of this application; Figure 4 This is a lateral cross-sectional schematic diagram of the seepage prevention and reinforcement construction process of the soil surrounding the tunnel in the embodiments of this application.

[0034] Specifically, such as Figures 1-4 As shown, the method for seepage prevention and reinforcement of the soil surrounding a tunnel provided in this application includes steps (1) to (5).

[0035] Step (1): Perform three-dimensional scanning modeling of the tunnel lining 7 and secondary grouting holes to obtain three-dimensional information of the secondary grouting holes. Conduct geological exploration of the soil 1 surrounding the tunnel to identify and classify different levels of weak permeability areas.

[0036] Step (2): Through the secondary grouting holes, the anode electrode 4, auxiliary electrode 3 and cathode electrode 2 are arranged in an alternating manner along the tunnel circumference.

[0037] Step (3): Install independent calcium source pipes 5 and carbon source pipes 6 along the tunnel axis, wherein the calcium source pipes 5 and carbon source pipes 6 are provided with openings.

[0038] Step (4): Calcium source solution and carbon source solution are released into the soil outside the tunnel through calcium source pipe 5 and carbon source pipe 6. At the same time, control voltage and current are applied to anode electrode 4, auxiliary electrode 3 and cathode electrode 2 to drive ions in calcium source solution and carbon source solution to migrate in a direction under the action of electric field and react to generate cement in the weak permeability area, thereby realizing soil reinforcement and seepage prevention.

[0039] Step (5): Check the reinforcement effect, remove the electrode, calcium source tube 5 and carbon source tube 6, and seal the secondary grouting hole.

[0040] In this embodiment, the application identifies weak permeability areas through 3D scanning modeling and geological exploration. By using electrodes arranged in a staggered pattern with secondary grouting holes and axially arranged independent calcium and carbon source pipes with holes, combined with electric field-driven ion directional migration, the calcium and carbon sources react precisely in the target area to generate cement. This achieves efficient soil reinforcement and seepage prevention in one integrated manner, while reducing additional construction disturbance by utilizing the existing grouting hole layout. Moreover, the materials are green, environmentally friendly, and pollution-free, with rapid reaction and high reinforcement strength. This effectively solves the problems of poor geological adaptability and uneven reinforcement of traditional technologies, and significantly improves tunnel construction safety and engineering durability.

[0041] In some embodiments, step (1) involves performing a three-dimensional scanning model of the tunnel lining 7 and the secondary grouting holes to obtain the three-dimensional information of the secondary grouting holes, and conducting geological exploration of the soil surrounding the tunnel 1. Specifically, this includes:

[0042] 1. High-precision tunnel structure modeling:

[0043] A 3D laser scanner was used to perform a full-range scan of the tunnel lining and secondary grouting holes, generating a 3D model and marking the lining thickness (30cm-50cm), circumferential length, and grouting hole distribution. The 3D model was used to extract the 3D coordinates, hole depth (2m-5m), hole diameter (50mm-80mm), and hole spacing (1m-1.5m) of the grouting holes.

[0044] 2. Geological exploration of the soil surrounding the tunnel:

[0045] Shallow layer (0-1m): Infrared detectors are used to quickly locate the surface and shallow weak areas, and to detect the surface water content and internal cavities.

[0046] Medium-deep layers (1m-10m): Ground penetrating radar is used to identify cavities, fissures, and loose layers in the soil.

[0047] Borehole sampling: Samples are taken around the grouting holes to test porosity, permeability coefficient, and pH value. This multi-technology collaboration enables precise location of areas with weak permeability. These areas refer to soil regions that, relative to the background soil conditions surrounding the tunnel, exhibit significant deterioration in structural integrity, hydraulic stability, or mechanical properties, and possess potential or existing risks of seepage and deformation. This is achieved through the comparison of the permeability coefficient k and the background permeability coefficient k. bg The permeability coefficient k can be determined through indoor permeability tests or borehole pressure tests. Background permeability coefficient k bg The median or geometric mean of the permeability coefficients from multiple measuring points within the same stratum, identified as non-anomaly zones, is taken. This is when the permeability coefficient of a certain area satisfies k ≥ 2~5k. bg When this occurs, the area is determined to be a weak permeability area or the degree of weakness has significantly increased.

[0048] Geological exploration of the soil surrounding the tunnel 1 was conducted using infrared detection, ground-penetrating radar, and borehole sampling to determine the spatial location and radial depth range of the weak permeability zones. Specifically, ground-penetrating radar was used to identify cavities, fissures, or loose zones in the soil and to determine the starting and ending depth ranges of the anomalous zones; borehole sampling was used to verify the anomalous zones and correct their depth ranges. Based on the above exploration results, the depth range and central index of the weak permeability zones were directly determined.

[0049] In some embodiments, based on the above exploration results, areas with low permeability are classified into slightly low-permeability areas, moderately low-permeability areas, and severely low-permeability areas. Slightly low-permeability areas are regions with anomalies in permeability coefficient k but without a continuous distribution; moderately low-permeability areas are regions with anomalies in permeability coefficient k forming a continuous anomalous zone; severely low-permeability areas are regions with permeability coefficient k reaching or exceeding 1×10⁻⁶. -4m / s, or areas where obvious seepage channels or large-scale loose structures have formed. The permeability coefficient k is obtained through indoor permeability tests or borehole pressure tests.

[0050] Specifically, the aforementioned "abnormality" refers to a soil permeability coefficient k not less than 1×10⁻⁶. -5 m / s; The above-mentioned "continuous abnormal zone" refers to a permeability abnormal zone that is continuously distributed along the depth for a length of not less than 1.0 m, or covers not less than two adjacent detection well sections in the circumferential direction.

[0051] In some embodiments, prior to step (2), the secondary grouting holes are cleaned, cleared, and a dispersant solution is injected to improve the permeability of the soil surrounding the secondary grouting holes. Optionally, the dispersant includes a polycarboxylate-based dispersant.

[0052] Exemplarily, this application provides a specific method for treating secondary grouting holes: First, a high-pressure plunger pump is connected to inject clean water into the secondary grouting hole for flushing, while simultaneously using an endoscope to check the cleanliness of the hole; after the cleanliness meets the standard, the hole opening is closed, and compressed air is injected into the hole, with pressure gauge data used to monitor whether there is any blockage in the hole; if the hole is determined to be unblocked, a polycarboxylate dispersant solution with a mass fraction of 0.5%-1.0% is injected into the hole at a low speed using a peristaltic pump, with the solution dosage being 1.0-2.0 L / m based on the hole depth; after injection, the hole is allowed to stand for 10-30 minutes. The role of the polycarboxylate dispersant is to disperse fine particles adhering to the hole wall, reduce the flow friction of subsequent calcium and carbon source solutions, weaken the tendency of mud cake to block the hole, and thus improve the permeability of subsequent calcium and carbon source solutions in the soil surrounding the tunnel.

[0053] In some embodiments, the specific layout and installation operations of the anode electrode 4, the auxiliary electrode 3 and the cathode electrode 2 in step (2) are as follows: a single-hole single electrode + multi-hole circumferential staggered layout method is adopted, that is, only one of the anode electrode 4, the cathode electrode 2 and the auxiliary electrode 3 is installed in each secondary grouting hole. Through the circumferential staggered arrangement of different types of electrodes, a stable electric field and ion directional migration path are formed.

[0054] The specific installation operation of the electrode is as follows: only one type of electrode of the corresponding type is installed in each hole. The electrode is fixed at the designed depth position by an insulating positioning bracket. Fine-particle bentonite is filled around the electrode and fully compacted to ensure continuous contact between the electrode, the hole wall and the soil, thus ensuring the conductivity of the electrode.

[0055] Preferably, the lengths of the three types of electrodes are consistent, and the electrode lengths are adjusted according to the spacing between the weak permeability area and the tunnel lining. The outer diameter / cross-sectional dimensions of the electrodes are classified according to structural type: rod-shaped electrodes are 10mm-20mm, and tubular mesh electrodes are 20mm-35mm. The electrode surface is coated with a RuO2 conductive layer or uses a corrosion-resistant titanium-based coating. The electrode leads are equipped with moisture-resistant insulating sheaths and waterproof caps to improve the corrosion resistance and safety of the electrodes. The installation depth of each type of electrode within the borehole is determined by the center depth of the weak permeability area. The center depths of the cathode electrode 2, auxiliary electrode 3, and anode electrode 4 are aligned with the center depth of the weak permeability area, with an allowable deviation of ±0.2m.

[0056] Furthermore, the electrode leads extend into the tunnel through a pre-designed waterproof sealing structure at the orifice, reliably connecting to the corresponding polarity interface of battery 8. The anode electrode 4 connects to the positive terminal of battery 8, the cathode electrode 2 to the negative terminal, and the auxiliary electrode 3 to the pre-designated adjustment interface of battery 8. The connection points are sealed with waterproof insulating tape to prevent moisture-induced short circuits. Simultaneously, the electrode leads establish a signal connection with the data acquisition module of the control system 9. This control system 9 integrates a voltage / current regulation unit, a real-time monitoring unit, and a feedback control unit. It can preset and accurately output parameters such as the voltage difference and current density between electrodes, and simultaneously acquire data on electrode operating status, soil pH, temperature, and resistivity change rate. When the monitored data exceeds a preset threshold, it automatically triggers voltage / current regulation or an alarm function to ensure a stable and controllable electric field driving process.

[0057] In some embodiments, such as Figure 2 As shown, the anode electrode 4, auxiliary electrode 3, and cathode electrode 2 are arranged in a repeating pattern along the tunnel circumference, such that at least one auxiliary electrode 3 is provided between any two adjacent anode electrodes 4 and cathode electrodes 2.

[0058] Preferably, the spacing between the grouting holes corresponding to each electrode is maintained at 1m-1.5m. When the weak zone of the soil around the tunnel is widely distributed, the proportion of auxiliary electrodes can be increased accordingly to meet the electric field construction requirements of the wide weak zone.

[0059] Furthermore, after the electrodes are installed, pre-energization testing is required: first, conduct no-load testing to check the output stability of voltage and current and the accuracy of data acquisition; then, conduct short-time energization testing to check the contact resistance and temperature rise of the electrodes in each grouting hole. If abnormal temperature rise occurs, fine-particle bentonite should be added for compaction or the electrode installation position should be adjusted. At the same time, check the mapping table of hole number and electrode type to ensure that the circumferential staggered sequence of the electrodes meets the design requirements.

[0060] In some embodiments, in step (3), the independent calcium source pipe 5 and carbon source pipe 6 are arranged along the tunnel axis, wherein the operation of providing openings on the calcium source pipe 5 and carbon source pipe 6 specifically includes: Figures 3-4 As shown, independent calcium source pipes 5 and carbon source pipes 6 are arranged along the tunnel axis. Calcium source pipe 5 is arranged between anode electrode 4 and auxiliary electrode 3, and carbon source pipe 6 is arranged between auxiliary electrode 3 and cathode electrode 2. Openings are provided on the side of calcium source pipe 5 and carbon source pipe 6 facing the adjacent auxiliary electrode 3.

[0061] Furthermore, the axes of both the calcium source pipe 5 and the carbon source pipe 6 are parallel to the longitudinal direction of the tunnel and are fixed to the outside of the tunnel lining 7 or in the extension groove inside the borehole via dedicated guide brackets. The calcium source pipe 5 and the carbon source pipe 6 are arranged parallel to each other and form a lateral coupling relationship of "source pipe—soil—electrode" with their corresponding electrodes, rather than being coaxially arranged. This avoids direct short-circuiting of the source liquid to the electrodes. The distance between the calcium source pipe 5 and the carbon source pipe 6 is controlled at 0.5m-0.75m. Simultaneously, the calcium source pipe 5 and the carbon source pipe 6 are respectively delivered at constant flow using micro-metering pumps, and each is equipped with a flow meter for closed-loop calibration, ensuring the control accuracy of solution delivery is ≤±5%.

[0062] Specifically, the calcium source tube 5 and the carbon source tube 6 have openings on the side facing the adjacent auxiliary electrode 3. The openings are located in the effective liquid release section of the calcium source tube 5 and the carbon source tube 6 corresponding to the auxiliary electrode 3. The effective liquid release section is a specific functional section on the side of the calcium source tube 5 and the carbon source tube 6 facing the auxiliary electrode 3. The length of the effective liquid release section is 0.6m-1.0m, and the center of the effective liquid release section corresponds to the auxiliary electrode 3. The remaining sections of the calcium source tube 5 and the carbon source tube 6 are fully enclosed (to prevent ineffective diffusion of calcium source solution and carbon source solution along the tunnel axis).

[0063] Preferably, the aperture of the opening is 0.6mm-1.2mm. Along the tunnel axial direction, the distance between adjacent openings is 20mm-40mm. Along the circumferential direction of the calcium source pipe 5 or carbon source pipe 6, the angle range of the opening is ≤120°.

[0064] In some embodiments, in step (4), a calcium source solution is released into the soil surrounding the tunnel through the calcium source pipe 5, and a carbon source solution is released into the soil surrounding the tunnel through the carbon source pipe 6. The calcium source solution is a mixed aqueous solution comprising water-soluble calcium salts and a nucleation regulator; the carbon source solution is an aqueous solution comprising water-soluble carbonates.

[0065] Furthermore, the concentration of water-soluble calcium salt in the calcium source solution is 0.6 mol / L-1.5 mol / L; the concentration of nucleating regulator in the calcium source solution is 0.5 g / L-10 g / L; and the concentration of water-soluble carbonate in the carbon source solution is 0.6 mol / L-1.5 mol / L.

[0066] Preferably, the water-soluble calcium salt includes calcium chloride; the nucleation regulator includes at least one of carboxymethyl chitosan, L-aspartic acid, and boric acid; and the water-soluble carbonate includes sodium carbonate.

[0067] In some embodiments, the release rates of the carbon source solution and calcium source solution in the calcium source tube 5 and carbon source tube 6 are determined according to the level of the permeability-weak region. Specifically, in the slightly weak region, the release rate of the carbon source solution and calcium source solution is 0.1 L / min-0.2 L / min, and the release time lasts for 4 h-6 h; in the moderately weak region, the release rate of the carbon source solution and calcium source solution is 0.3 L / min-0.4 L / min, and the release time lasts for 6 h-8 h; in the severely weak region, the release rate of the carbon source solution and calcium source solution is 0.4 L / min-0.5 L / min, and the release time lasts for 8 h-10 h.

[0068] In some embodiments, step (4), the operation of applying control voltage and current to the anode electrode 4, auxiliary electrode 3 and cathode electrode 2 specifically includes:

[0069] 1. First, set the electrode base voltage difference to 2V-5V. This voltage difference is adjusted according to the distance between the electrode and the weak permeability area. The voltage difference in the near zone (the area closer to the tunnel lining 7) is controlled at 2V-3V, and the voltage difference in the far zone (the area farther from the tunnel lining 7) is controlled at 3V-5V. The specific voltage difference can be adjusted according to the actual situation. The overall voltage difference is allowed to deviate by ±0.5V to ensure that the coverage area of ​​the calcium source solution and carbon source solution is ≥90%.

[0070] 2. Simultaneously, apply 10 mA / cm to the auxiliary electrode 3. 2 -20mA / cm 2 The current is used to monitor the pH and temperature of the soil environment in real time, with the target pH range being 11-12 and the temperature controlled between 20℃ and 30℃.

[0071] 3. Maintain an Amplitude of 10 mA / cm between the cathode and anode. 2 -15mA / cm 2 The current density is maintained for 2-3 hours. After the current is turned on, the voltage is reduced by 0.2V-0.3V every 30 minutes until it drops to 0V, in order to ensure the uniformity of soil solidification.

[0072] Preferably, during the entire power-on process, the distribution of the calcium source solution and carbon source solution is scanned with ground penetrating radar every 30 minutes. If a deviation in the distribution of the calcium source solution and carbon source solution is found, the electrode voltage is adjusted in time to achieve directional control of the migration of the calcium source solution and carbon source solution.

[0073] In some embodiments, during the energization process in step (4), considering that an electrolysis reaction may occur near the cathode electrode 2 and the auxiliary electrode 3 under negative bias, generating gas (H2), a drainage and venting structure needs to be provided to ensure the safe operation of the system, as follows: Figures 2-4As shown, a drainage and exhaust hose 10 is installed parallel to the electrodes in the secondary grouting hole where the cathode electrode 2 and the auxiliary electrode 3 under negative bias are installed, for discharging water and gas generated during the electrolysis process.

[0074] Alternatively, the outer diameter of the drainage and venting hose 10 is 8mm-12mm. It is arranged in the same hole as the electrode and extends parallel to the axial direction of the grouting hole. It is fixed to the hole wall by an insulating support structure so that the drainage and venting hose 10 and the electrode maintain a preset distance to avoid contact between them or electrical short circuit.

[0075] The lower end of the drainage and venting hose 10 is located 10cm-30cm above the lower end of the electrode, ensuring efficient discharge of water and gas generated by the electrolysis reaction and accumulated in the borehole without disturbing the contact between the electrode and the soil or affecting the mineralization and deposition process. The upper end of the drainage and venting hose 10 extends to the borehole opening and is connected to the water collection tank through a water collection cap.

[0076] During drainage, a miniature pump is used for intermittent pumping, preferably for 2-5 minutes every 30-60 minutes, to maintain a water-free environment in the well. Waste liquid collected in the collection tank must be neutralized to pH 6-9 before being transported for disposal.

[0077] Meanwhile, the orifice must be equipped with a one-way exhaust valve or intermittent venting device, specifically for venting the gas generated during the electrolysis process. The orifice must not be in a closed operating state to prevent gas accumulation and potential safety risks.

[0078] In some embodiments, in step (5), the reinforcement effect is detected after the reinforcement is completed. The specific operations include:

[0079] 1. Conduct reinforcement effect testing: Use a water pressure testing device to determine the soil permeability coefficient and evaluate the seepage prevention effect; drill soil samples after reinforcement and test their unconfined compressive strength (UCS) to verify the improvement of mechanical properties; at the same time, use a resistance meter to measure the soil resistivity change rate under 0.5V voltage conditions to help evaluate the solidification uniformity and reinforcement effect.

[0080] 2. After the reinforcement effect is qualified, the finishing treatment is carried out: remove the electrode, calcium source tube 5 and carbon source tube 6, clean the residue at the opening of the secondary grouting hole, and use a cement grouting machine to inject sealing material into the hole to seal the opening and smooth it.

[0081] Furthermore, to ensure the long-term stability of the project, it is recommended to use ground-penetrating radar to re-inspect the reinforced area every 6-8 months to assess the stability of the soil. If the reinforcement effect is found to be weakened or there are potential hazards, secondary reinforcement treatment should be implemented if necessary.

[0082] In summary, the method for seepage prevention and reinforcement of the soil surrounding a tunnel provided in this application combines biomimetic mineralization-induced calcium carbonate precipitation (BCICP) technology with electroosmosis. It constructs a three-electrode array using secondary grouting holes in the tunnel, and combines multi-technology collaborative exploration to accurately locate weak seepage areas. It also uses independent calcium source pipes and carbon source pipes to precisely and quantitatively release calcium source solution and carbon source solution. The electric field guides the directional migration of ions and reacts in the target weak area to generate calcium carbonate cement, thereby achieving efficient seepage prevention and reinforcement of the soil surrounding the tunnel.

[0083] This application effectively overcomes the shortcomings of traditional reinforcement technologies in terms of uniformity and adaptability by coupling electroosmosis with BCICP technology and using a three-electrode array design. Relying on the synergistic cooperation of calcium source tubes, carbon source tubes and three-electrode arrays, it achieves precise release of cementing fluid and directional ion reaction, fully ensuring the targeted nature of reinforcement and seepage prevention. At the same time, through multi-technology exploration and graded control, a dynamic reinforcement mechanism is formed, coupled with long-term monitoring and re-inspection schemes, which not only ensures the stability and traceability of the reinforcement effect, but also significantly improves the construction safety and long-term durability of tunnel engineering.

[0084] This application provides a method for seepage prevention and reinforcement of soil surrounding tunnels, which specifically addresses the problems of high cost, significant pollution, and insufficient uniformity and adaptability of existing tunnel seepage prevention and reinforcement technologies. It offers significant advantages: First, it is lower in cost, fully utilizing existing secondary grouting holes to reduce the need for additional drilling; electrodes can be partially recovered; and the dosage of calcium and carbon source solutions is precisely controlled via a micro-metering pump, avoiding waste. Second, it is environmentally friendly, using materials free of heavy metals and other pollutants; the reaction product is natural calcium carbonate, which is beneficial to the soil and surrounding environment. Third, it is more efficient, with electroosmosis driving ion migration to accelerate the reaction; and multiple technologies, including infrared detection, ground-penetrating radar, and borehole sampling, are used in synergistic exploration to accurately locate weak areas and avoid blind construction. Fourth, it has strong applicability; by adjusting the voltage difference, current density, and release rate of the calcium and carbon source solutions, it can be adapted to light / medium / severely weak areas and soils of different depths and permeability coefficients, resulting in stable reinforcement effects.

[0085] The present application is further illustrated below through embodiments and related test experiments. In the detailed description below, numerous specific details are set forth for ease of explanation to provide a comprehensive understanding of the embodiments of the present application. However, it is apparent that one or more embodiments may be implemented without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict. All instruments, consumables, and reagents used in the following embodiments are commercially available unless otherwise specified.

[0086] Example 1

[0087] Sampling and testing were conducted on the soil surrounding a tunnel in a certain area. Taking the borehole sampling results at the tunnel arch as an example, the specific sampling and testing results are shown in Table 1.

[0088] Table 1. Sampling and testing results of tunnel arch in Example 1

[0089]

[0090] The test results show that the soil in this area has a high moisture content and a significantly high permeability coefficient, indicating a clear risk of seepage.

[0091] A comprehensive geological exploration of the soil surrounding the tunnel was conducted using infrared detection, ground-penetrating radar (GPR), and borehole sampling. GPR results showed a continuous anomalous reflection zone within a depth range of 3.0m-4.5m from the outer surface of the tunnel lining. To determine the degree of permeability anomaly, multiple measuring points in the same stratum, previously identified as non-anomaly zones by infrared detection and GPR, were compared and tested; their permeability coefficients were concentrated around 1.6 × 10⁻⁶. -3 cm / s to 2.1×10 -3 Between cm / s, take the median of 1.9 × 10. -3 cm / s as the background permeability coefficient k bg A comparative analysis of the permeability coefficient of the target area with the background value shows that the permeability coefficient of the target area satisfies k ≥ 1 × 10⁻⁶. -3 cm / s, and k / k bg The value is approximately 4.53, which meets the criteria for determining abnormal permeability and significantly increased weakness.

[0092] After identifying the permeability anomaly, the spatial distribution characteristics of the anomaly were further determined. Ground-penetrating radar results showed that the continuous radial distribution length of the anomaly zone was 1.5 m, exceeding the 1.0 m threshold required for determining a continuous anomaly zone. Simultaneously, the anomaly reflection zone covered multiple adjacent secondary grouting borehole sections in the circumferential direction, satisfying the criteria for determining a continuous spatial distribution of the anomaly along both depth and circumference. Combined with borehole sampling results, it was confirmed that the overall soil permeability within the anomaly zone was high, and the anomaly exhibited significant spatial continuity, rather than being a localized isolated anomaly.

[0093] Based on the analysis of the degree of permeability anomaly and its spatial continuity, it can be determined that this region not only exhibits permeability anomalies, but these anomalies have also developed into a continuous anomaly zone, posing a potential risk of forming seepage channels. Furthermore, the representative permeability coefficient of this region has reached 8.6 × 10⁻⁶. -3 cm / s, significantly higher than 1×10 -3 The area is classified as a severely weak zone because it meets the reference threshold of cm / s and has a high soil moisture content, which provides the hydraulic conditions for further seepage development.

[0094] Based on the upper and lower boundaries of the anomalous reflection zone and the verification results of borehole sampling, the radial depth range of the weak zone was determined to be 3.0m-4.5m. Using the midpoint of this depth range as the center index of the weak zone, the center depth of the weak zone was found to be approximately 4.0m. Based on this, the treatment thickness was determined to be ±0.5m of the center depth, i.e., 3.5m-4.5m. This range completely covers the continuous anomalous zone identified by ground-penetrating radar.

[0095] After determining the level of weak areas and the depth of the center, a 3D laser scanning robot was used to scan the tunnel arch lining and secondary grouting holes, generating a digital twin model. The scan results showed that the tunnel lining thickness was 40cm, the circumferential spacing of the secondary grouting holes in the arch was 1.2m, the hole depth was 4.5m, and the hole diameter was 70mm. An endoscope inspection of the ducts revealed no obvious collapses or foreign object blockages, and the duct conditions met the requirements for subsequent construction.

[0096] Based on the permeability characteristics and reinforcement requirements of severely weakened areas, calcium and carbon source solutions were prepared for electro-chemical reinforcement. The calcium source solution consisted of a 1.0 mol / L aqueous solution of calcium chloride, with carboxymethyl chitosan added as a nucleation regulator at a concentration of 6 g / L to induce calcium carbonate nucleation and control deposition morphology. The carbon source solution was a 1.0 mol / L aqueous solution of sodium carbonate, with the same concentration as the calcium source solution. The calcium and carbon source solutions were stored separately, prepared fresh each time, and controlled by independent metering pumps to avoid premature mixing and reaction.

[0097] Both the calcium source pipe and the carbon source pipe are made of high-polymer conductive composite material. In severely weak areas, a main pipe and an internal release branch pipe structure are used. The release branch pipe has an inner diameter of approximately 3.5 mm, an outer diameter of approximately 5 mm, and a length of 4.5 m. The calcium source pipe and the carbon source pipe are arranged parallel to the tunnel axis and fixed in the extension groove on the outside of the lining by guide brackets. The lateral spacing between the two pipes is 0.6 m. The calcium source pipe and the carbon source pipe only have openings in the effective release section corresponding to the auxiliary electrode. The effective release section is 0.8 m long, and its center position corresponds to the center depth of the auxiliary electrode. The hole diameter is 0.8 mm, the axial hole spacing is 30 mm, and the circumferential opening angle is 120°. The rest of the circumferential direction is closed to avoid ineffective diffusion of the calcium source solution and the carbon source solution along the tunnel axis.

[0098] Before installing the electrodes, the boreholes were treated. A high-pressure plunger pump was used to inject clean water into the borehole for flushing, and the borehole wall integrity was checked using an endoscope. The boreholes were then purged with compressed air to confirm patency. Next, a 0.5% polycarboxylate-based dispersant was injected into the borehole at a rate of 1.5 L / m. After injection, the borehole was allowed to stand for 10 minutes to disperse fine particles on the borehole wall, reduce friction, and mitigate the tendency for mud cake to clog.

[0099] Electrodes are installed using a single-hole, single-electrode arrangement, staggered in the circumferential direction. The anode, cathode, and auxiliary electrodes are all fixed at the designed depth using insulated positioning brackets, with their center depth aligned with the center depth of the weakest area (4.0m), allowing a deviation of ±0.2m. The electrodes are arranged in a repeating sequence along the tunnel circumference, starting with the anode, then the auxiliary electrode, and finally the cathode, with a 1.2m spacing between adjacent electrodes. Fine-grained bentonite is filled around the electrodes and compacted to ensure continuous contact between the electrodes, the borehole wall, and the soil.

[0100] During the reinforcement process, the central control system was set to an electrode voltage of 2.0V, and the release rate of the calcium and carbon source solutions was 0.5L / min, continuously released for 8 hours, with a cumulative release volume of 240L, including 120L each of calcium and carbon source solutions. Real-time monitoring was conducted using a flow meter during the release process, with actual flow fluctuations controlled within ±5%. The electrode voltage difference was set to 5.0V, and the distribution of the cementing fluid was scanned using ground-penetrating radar every 30 minutes to ensure uniform distribution within a depth range of 3.0m-4.5m. When insufficient distribution occurred in local areas, the voltage was adjusted within an allowable deviation of ±0.5V for directional control. A 19mA / cm² voltage was applied to the auxiliary electrodes via the control system. 2 The current density is maintained at 10 mA / cm at both the anode and cathode electrodes. 2 -15mA / cm 2 After energizing for 2 hours, the voltage of the composite tube was gradually reduced to 0V at a rate of 0.2V / 30min to ensure uniform curing. The soil pH and temperature were monitored in real time during the reaction. The pH remained stable within the range of 11-12, and the highest temperature reached 28℃, not exceeding 30℃.

[0101] Considering the potential for water and gas precipitation near the cathode and the auxiliary electrode under negative bias, drainage and venting hoses with an outer diameter of 10 mm were installed in the secondary grouting holes of the cathode electrode and the corresponding auxiliary electrode. These hoses were arranged parallel to the electrode along the hole axis, with their lower ends approximately 20 cm above the lower end of the electrode. A micro-pump was used for intermittent drainage, with a drainage frequency of once every 30-60 minutes, each drainage lasting 2-5 minutes. No significant water accumulation occurred in the holes during operation. A water collection cap was installed at the hole opening and connected to a collection tank. A one-way venting valve was also installed to prevent gas accumulation. The waste liquid was neutralized to pH 6-9 before being transported for disposal.

[0102] The reinforcement effect was tested after curing. A water pressure testing device was used, and the permeability coefficient was measured to be 3.2 × 10⁻⁶ under a pressure of 0.2 MPa. -8 cm / s, less than the design requirement of 5×10 -8cm / s; after drilling and reinforcing, soil samples were subjected to unconfined compressive strength tests, and the UCS was measured to be 2.1 MPa, higher than the design requirement of 1.85 MPa; the resistance value was measured at 0.5V, which increased by 65% ​​compared with the initial value, exceeding the 50% judgment threshold. The above test results indicate that the seepage prevention and reinforcement effect in this area is significant, and all indicators meet the design requirements.

[0103] After reinforcement, the electrodes, calcium source pipe, and carbon source pipe were removed. Residual material at the borehole opening was cleaned, and cement grout was injected into the borehole using a cement grouting machine for sealing and smoothing. Following the completion of construction, a ground-penetrating radar re-inspection of the area was conducted every 6 months as planned. The initial re-inspection showed a permeability coefficient of 3.5 × 10⁻⁶. -8 The flow rate was measured in cm / s, no new weak points were found, the reinforcement effect was stable, and no secondary reinforcement was required.

[0104] Example 2

[0105] Sampling and testing were conducted on the soil surrounding a tunnel in a certain area. Taking the soil sampling results at the bottom of the tunnel invert as an example, the specific sampling and testing results are shown in Table 2.

[0106] Table 2 Sampling and testing results of tunnel arch in Example 2

[0107]

[0108] The test results indicate that the soil in this area has a high moisture content and high permeability, posing a potential risk of seepage.

[0109] A comprehensive inspection of the tunnel invert area was conducted using 3D laser scanning, ground-penetrating radar (GPR), and borehole sampling. 3D laser scanning results showed that the initial lining thickness was approximately 38 cm, the secondary grouting holes had a longitudinal spacing of 1.5 m, a depth of 3.5 m, a diameter of 60 mm, and an intact duct structure. GPR results indicated a continuous but moderately strong anomalous reflection zone within a depth range of 2.5 m to 3.5 m from the outer edge of the tunnel lining. Combined with the results of segmented borehole sampling, the soil porosity within this depth range was approximately 32%, the pH value was approximately 6.8, and the permeability coefficient was significantly higher than the surrounding area, with a local maximum value reaching 8.5 × 10⁻⁶. -6 cm / s.

[0110] To determine the degree of permeability anomaly, multiple measuring points within the same stratum that were previously identified as non-anomaly zones were selected for comparison, with their permeability coefficients concentrated around 1.8 × 10⁻⁶. -6 cm / s to 2.6 × 10 -6 Between cm / s, the median is taken as the background permeability coefficient k. bg Comparative analysis shows that the permeability coefficient in the abnormal section satisfies k ≥ 1 × 10⁻⁶. -3 The anomaly detection criteria for cm / s, and the local region k / kbg A permeability coefficient increase of 2-3 times indicates a significant deterioration in the soil's permeability in this area. Furthermore, the continuous radial length of this anomalous zone exceeds 1.0m, and it covers multiple adjacent borehole sections in the circumferential direction, meeting the criteria for a continuous anomalous zone. Considering both the degree of permeability anomaly and its spatial continuity, this area is classified as a moderately weak zone.

[0111] Based on the upper and lower boundaries of the ground-penetrating radar anomaly zone and the verification results of borehole sampling, the radial depth range of the weak zone was determined to be 2.5m-3.5m. Using the midpoint of this depth range as the center index of the weak zone, the center depth of the weak zone was found to be approximately 3.0m. Based on this, the treatment range was determined to be 2.5m-3.5m, which completely covers the detected and identified anomaly section.

[0112] After determining the level of areas with poor permeability, calcium and carbon source solutions were prepared based on the permeability characteristics and reinforcement requirements of moderately weak areas. The calcium source solution consisted of a calcium chloride aqueous solution at a concentration of 0.8 mol / L, with L-aspartic acid selected as a nucleation regulator at a concentration of 8 g / L to induce rapid nucleation of calcium carbonate and improve its dispersibility in clay pores. The carbon source solution consisted of a sodium carbonate aqueous solution at the same concentration as the calcium source solution, 0.8 mol / L, with 0.05% silane coupling agent added to enhance the interfacial bonding between mineralization products and clay particles. The calcium and carbon source solutions were stored separately, prepared and used immediately, and controlled by independent metering pumps to avoid premature mixing.

[0113] Both the calcium source pipe and the carbon source pipe are made of high-polymer conductive composite material. In moderately weak areas, a main pipe and an internal liquid release branch pipe structure are used. The liquid release branch pipe has an inner diameter of approximately 3.0 mm, an outer diameter of approximately 5.0 mm, and a length of 3.5 m. The calcium source pipe and the carbon source pipe are arranged parallel to each other along the tunnel axis and fixed by guide supports. The lateral spacing between the two pipes is 0.75 m. The calcium source pipe and the carbon source pipe only have openings in the effective liquid release section corresponding to the auxiliary electrode. The length of the effective liquid release section is 0.7 m, and its center position corresponds to the center depth of the auxiliary electrode. The opening direction is towards the auxiliary electrode, the hole diameter is 0.8 mm, the axial hole spacing is 30 mm, the circumferential opening angle is no greater than 120°, and the rest of the circumferential direction is closed.

[0114] Before installing the electrodes, the pores were pretreated. A high-pressure plunger pump was used to inject clean water into the pores at a pressure of 1.0 MPa for rotary flushing at a flow rate of 6 L / min for 7 minutes. The integrity of the pore walls was then inspected using an industrial endoscope. Next, the pores were purged with compressed air at 0.3 MPa, with the pressure stabilizing from 0.30 MPa to 0.29 MPa, confirming pore patency. Subsequently, a 0.5% (w / w) polycarboxylate-based dispersant was injected into the pores at a volume of 120 mL using a metering peristaltic pump. The pores were then allowed to stand for 12 minutes to improve pore wall wetting and reduce the risk of localized blockage.

[0115] Electrodes are installed using a single-hole, single-electrode arrangement, staggered in the circumferential direction. The anode, cathode, and auxiliary electrodes are all fixed at the designed depth using insulated positioning brackets, with their center depth aligned 3.0m with the center depth of the weakest area, allowing a deviation of ±0.2m. The anode, auxiliary, and cathode electrodes are arranged in a repeating sequence along the tunnel circumference, maintaining the designed spacing between adjacent electrodes. Fine-grained bentonite is filled around the electrodes and compacted to ensure continuous contact between the electrodes, borehole walls, and the soil.

[0116] During the reinforcement process, the central control system was set to an electrode voltage of 1.8V, and the release rates of the calcium and carbon source solutions were controlled within the range of 0.3L / min-0.4L / min. The actual monitored release rate was 0.33L / min-0.37L / min, with continuous release for 7 hours and a cumulative release of approximately 150L. Due to the relatively low stability of L-aspartic acid in solution, the calcium source solution replacement cycle was shortened, with a fresh solution prepared every 1.5 hours. The electrode voltage difference was set to 3.5V, and the distribution of the cementing solution was scanned using high-frequency ground-penetrating radar every 30 minutes. The results showed that the cementing solution diffused slowly and was evenly distributed within a depth range of 2.5m-3.5m. When the 3.5-hour scan revealed a slightly lower cementing solution concentration at a depth of 3.2m, the voltage difference was adjusted to 4.0V within the allowable deviation range of ±0.5V, and subsequent scans showed that the distribution returned to uniformity.

[0117] Apply 15 mA / cm to the auxiliary electrode 2 The current density is maintained at 10 mA / cm at both the anode and cathode. 2 -15mA / cm 2 Power was applied, and a portable pH meter was used for real-time monitoring during the reaction. The soil pH gradually increased from 6.8 to 11.3 and remained stable within the 11-12 range. A thermometer was used to monitor the reaction temperature, with a maximum temperature of 27℃, not exceeding 30℃. The reaction continued for 7 hours, during which the pipeline connections were checked regularly, and no leaks were found. Subsequently, the current density was set to 10 mA / cm². 2 The electrode voltage was continuously applied for 2 hours, and then gradually reduced to 0V at a rate of 0.2V / 30min. After the curing was completed, no obvious cracks or bulges appeared on the surface of the soil.

[0118] Considering the possibility of water and gas precipitation near the cathode and the auxiliary electrode under negative bias, drainage and venting hoses were installed in the corresponding grouting holes and pumped out at regular intervals. No obvious water accumulation or blockage was observed in the holes during operation.

[0119] The reinforcement effect was tested after curing. A water pressure testing device was used, and the permeability coefficient was measured to be 8.5 × 10⁻⁶ under a pressure of 0.2 MPa. -9 cm / s, less than the design requirement of 1×10 -8 cm / s; after drilling and reinforcing, soil samples were subjected to unconfined compressive strength tests, and the UCS was measured to be 1.4 MPa, higher than the design requirement of 1.2 MPa; the resistance value was measured at 0.5V, which increased by 58% compared with the initial value, exceeding the 50% judgment threshold. The above test results indicate that the seepage prevention and reinforcement effect in this area meets the design requirements.

[0120] After reinforcement, the electrodes, calcium source pipe, and carbon source pipe were removed, debris at the borehole opening was cleaned, and cement grout was injected into the borehole using a cement grouting machine for sealing and smoothing. Following the completion of construction, a high-frequency ground-penetrating radar re-inspection was conducted every 6 months on the area at the bottom of the tunnel invert, as planned. The initial re-inspection showed a permeability coefficient of 9.2 × 10⁻⁶. -9 The flow rate was cm / s, no new weak areas were generated, and no reduction in the reinforcement effect was found in subsequent monitoring. Due to the strong stability of the clay, no additional reinforcement is required.

[0121] Example 3

[0122] Sampling and testing were conducted on the soil surrounding a tunnel in a certain area. Taking the soil around the tunnel sidewall as an example, the specific sampling and testing results are shown in Table 3.

[0123] Table 3. Sampling and testing results of tunnel arch in Example 3

[0124]

[0125] The test results show that the soil in this area has an extremely high permeability coefficient, belonging to a typical high-permeability stratum, and has a significant risk of forming strong seepage channels.

[0126] A comprehensive inspection of the tunnel sidewall area was conducted using 3D laser scanning, ground-penetrating radar (GPR), and borehole sampling. 3D laser scanning results showed that the initial lining thickness was approximately 45 cm, the longitudinal spacing of the secondary grouting holes was approximately 1.3 m, the hole depth was 5.0 m, the hole diameter was 80 mm, and the duct structure was intact. GPR detected scattered anomalous reflection zones within a depth range of 3.5 m to 5.0 m from the outer edge of the lining. Borehole sampling results indicated that the soil porosity within this depth range was approximately 42%, the pH value was approximately 7.0, and the local permeability coefficient reached 3.8 × 10⁻⁶. -2cm / s. To determine the degree of permeability anomaly, multiple measuring points within the same stratum, identified as non-anomaly zones, were selected for comparison. Their permeability coefficients were concentrated in the range of (0.9-1.5)×10⁻⁶ cm / s. -2 Between cm / s, take the median of 1.2 × 10⁻⁶. -2 cm / s as the background permeability coefficient k bg Comparative analysis shows that the permeability coefficient of the target area satisfies k ≥ 1 × 10⁻⁶. -3 The anomaly detection criteria for cm / s, and k / k bg ≈2.1, which satisfies k≥2-5k bg The criteria for identifying weak areas; simultaneously, the permeability coefficient of the target area is converted to 2.5 × 10⁻⁶. -4 m / s, has reached or exceeded 1×10 -4 Based on the criterion of severely weak zones using m / s, this area was comprehensively determined to be a severely weak zone. According to the depth range of the ground-penetrating radar anomaly reflection zone and the borehole sampling verification results, the radial depth range of the weak zone was determined to be 3.5m-5.0m. The center depth of the weak zone was taken as approximately 4.25m at the midpoint of the upper and lower boundaries. During implementation, the center depth of the weak zone was taken as approximately 4.2m, and the treatment range was 3.5m-5.0m.

[0127] After identifying the weak areas, the locations and conditions of the secondary grouting holes were verified. The holes were then pretreated by flushing them with clean water using a high-pressure plunger pump at a pressure of 1.2 MPa and a flow rate of 10 L / min for 8 minutes. After flushing, the hole wall condition was observed using an industrial endoscope, confirming minimal residual fine soil at the bottom. The holes were then purged with compressed air at 0.4 MPa for 5 minutes; a precision pressure gauge showed the pressure stabilized at 0.39 MPa from 0.40 MPa, indicating the holes were patent. Subsequently, a 0.5% polycarboxylate dispersant was injected into the holes using a metering peristaltic pump. The dosage, calculated based on the hole depth, was within the range of 1.0 L / m to 2.0 L / m, with a total injection volume of 400 mL. After injection, the holes were allowed to stand for 12 minutes to disperse fine particles on the hole wall and improve the subsequent infiltration conditions of the source solution. To slow down the rapid loss of cementing fluid in the high-permeability gravel layer, 100 mL of diluted nano-kaolin slurry was injected into the pores after the dispersant was applied. This filled the small pores on the gravel surface and was left to stand for 5 minutes to form a local pre-sealing layer.

[0128] The electrodes are arranged in a "single-hole single-electrode + multi-hole circumferential staggered" configuration. Anode, cathode, and auxiliary electrodes are all fixed at the designed depth using insulated positioning brackets. The center depth of each electrode is aligned with the center depth of the weak zone (4.2m), with an allowable deviation of ±0.2m. They are arranged in a repeating sequence along the tunnel sidewall, following the order of anode, auxiliary, and cathode electrodes, with a spacing of 1.3m between adjacent electrodes. Fine-grained bentonite is filled around the electrodes and compacted to ensure continuous contact between the electrodes, borehole wall, and soil. The effective length of all three types of electrodes is consistent and matched to the borehole depth. The electrode surface uses a RuO2 conductive layer or a corrosion-resistant titanium-based coating. The leads are fitted with moisture-resistant insulating sheaths and waterproof caps. After installation, no-load tests and short-term power-on checks are performed to confirm stable output and normal temperature rise.

[0129] Both the calcium and carbon source pipes are made of high-polymer conductive composite materials. In severely weak areas, a main pipe and an internal release branch pipe structure are used, with the release branch pipe having an outer diameter of 3mm-6mm and an inner diameter of 2mm-4mm. The two source pipes are arranged parallel to each other along the tunnel axis and fixed in the extension groove on the outside of the lining by guide brackets, with a lateral spacing of 0.6m between the two pipes. The two source pipes only have openings in the effective release section corresponding to the auxiliary electrode; the remaining sections are fully enclosed to prevent ineffective diffusion of the cementing fluid along the tunnel axis. The length of the effective release section is 0.9m, and its center position corresponds to the center depth of the auxiliary electrode with an allowable deviation of ±0.2m. The openings of the calcium and carbon source pipes in the effective release section are all oriented towards the auxiliary electrode, with a micropore diameter of 1.0mm, an axial hole spacing of 35mm, and a circumferential opening angle not exceeding 120°; the remaining circumferential sections are closed.

[0130] Calcium and carbon source solutions were formulated based on the permeability characteristics and reinforcement requirements of severely weakened areas. Considering the large porosity, high permeability, and rapid migration of calcium and carbon source solutions in gravelly soil, the concentrations of both solutions were selected within the higher range of 0.6 mol / L to 1.5 mol / L to ensure sufficient ion supply for the mineralization reaction. Simultaneously, to enhance the mechanical interlocking force in the coarse-grained skeleton, boric acid was chosen as a regulator to induce the formation of rough-surfaced calcium carbonate aggregates. The calcium source solution was a 1.2 mol / L aqueous solution of calcium chloride, with boric acid added to a concentration of 8 g / L. The carbon source solution was a 1.2 mol / L aqueous solution of sodium carbonate, with the same concentration as the calcium source solution, to avoid local reaction imbalance. The calcium and carbon source solutions were stored separately, prepared fresh each time, and controlled by constant flow using independent metering pumps, with closed-loop calibration using flow meters to ensure a control accuracy of no more than ±5%.

[0131] During the reinforcement process, the central control system was set to an electrode voltage of 2.0V, and the release rate of the calcium and carbon source solutions was 0.5L / min, continuously released for 8 hours, with a cumulative release volume of 240L. The release was monitored by a flow meter, and the actual flow rate was controlled within the range of 0.48L / min-0.52L / min. An electrode voltage difference of 5.0V was set, and high-frequency ground-penetrating radar was used every 30 minutes to scan the distribution of the calcium and carbon source solutions. The results showed that the calcium and carbon source solutions diffused slowly and were relatively uniformly distributed within a depth range of 3.5m-5.0m. When the concentration of calcium and carbon source solutions at a depth of 4.0m was found to be slightly low during the 5-hour scan, the voltage difference was adjusted to 5.5V within the allowable deviation range of ±0.5V, and subsequent scans showed that the distribution returned to uniformity. An application of 19mA / cm² was applied to the auxiliary electrode. 2 The current density was monitored in real time using a portable pH meter during the reaction. The soil pH value gradually increased from 7.0 to 11.6 and remained stable in the 11-12 range. The reaction temperature was monitored using a thermometer, with the highest temperature reaching 29℃ and not exceeding 30℃. The reaction lasted for 8 hours, and the pipeline connections were checked regularly during this period; no leaks were found.

[0132] Considering the potential for water and gas precipitation near the cathode and the auxiliary electrode under negative bias, drainage and venting hoses were installed in the corresponding holes, and timed pumping was performed. No significant water accumulation occurred in the holes during operation. After the reaction, electricity was continued for 2 hours to promote mineralization and solidification. Subsequently, the composite tube voltage was gradually reduced at a rate of 0.2V / 30min until 0V was reached to complete the solidification process. After solidification, no obvious cracking or collapse was observed on the soil surface, and ultrasonic testing revealed no discontinuous areas in the cemented material.

[0133] The reinforcement effect was tested after curing. A water pressure testing device was used, and the permeability coefficient was measured to be 6.8 × 10⁻⁶ under a pressure of 0.2 MPa. -8 cm / s, less than the design requirement of 8×10 -8 cm / s; after drilling and reinforcing, soil samples were subjected to unconfined compressive strength tests, and the UCS was measured to be 2.3 MPa, higher than the design requirement of 2.0 MPa; the resistance value was measured at 0.5V, which increased by 72% compared with the initial value, exceeding the 50% judgment threshold. The above test results indicate that the seepage prevention and reinforcement effect in this area meets the design requirements.

[0134] After reinforcement, the electrodes, calcium source pipe, and carbon source pipe were removed, debris at the borehole opening was cleaned, and cement grout was injected into the borehole using a cement grouting machine for sealing and smoothing. Following the completion of construction, a high-frequency ground-penetrating radar re-inspection of this area of ​​the tunnel sidewall was conducted every 6 months as planned. The initial re-inspection showed a permeability coefficient of 7.5 × 10⁻⁶. -8 The speed was cm / s, no new weak areas were generated, and no attenuation of the reinforcement effect was found in subsequent monitoring, indicating that the reinforcement effect was stable and no supplementary reinforcement was required.

[0135] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for seepage prevention and reinforcement of soil surrounding a tunnel, characterized in that, Includes the following steps: Step (1): Perform three-dimensional scanning modeling of the tunnel lining and secondary grouting holes, obtain the three-dimensional information of the secondary grouting holes, conduct geological exploration of the soil around the tunnel, and identify and classify different levels of weak permeability areas. Step (2): Through the secondary grouting holes, anode electrodes, auxiliary electrodes, and cathode electrodes are arranged in an alternating manner along the tunnel circumference; Step (3): Lay out independent calcium source pipes and carbon source pipes along the tunnel axis, wherein the calcium source pipes and the carbon source pipes are provided with openings; Step (4): Calcium source solution and carbon source solution are released into the soil surrounding the tunnel through the calcium source pipe and the carbon source pipe. At the same time, control voltage and current are applied to the anode electrode, the auxiliary electrode and the cathode electrode to drive the ions in the calcium source solution and carbon source solution to migrate in a direction under the action of the electric field and react to form cement in the weak permeability area, thereby realizing soil reinforcement and seepage prevention. Step (5): Detect the reinforcement effect, remove the electrodes, calcium source tube and carbon source tube, and seal the secondary grouting hole.

2. The method for seepage prevention and reinforcement of the soil surrounding a tunnel according to claim 1, characterized in that, The areas with weak penetration are classified into lightly weak areas, moderately weak areas, and severely weak areas according to their severity. The slightly weak area is a region where the permeability coefficient k is abnormal but not continuously distributed; The moderately weak zone is the area where the permeability coefficient k anomaly zone forms a continuous abnormal band; The severely weakened area is defined as a permeability coefficient k that reaches or exceeds 1×10⁻⁶. -4 m / s, or areas where obvious seepage channels or large-scale loose structures have been formed; The permeability coefficient k is obtained through indoor permeation tests or borehole pressure tests.

3. The method for seepage prevention and reinforcement of the soil surrounding a tunnel according to claim 1 or 2, characterized in that, The anode electrode, auxiliary electrode, and cathode electrode are arranged in an alternating manner along the circumference of the tunnel, including: The electrodes are arranged in a circumferential manner along the tunnel in the order of anode electrode, auxiliary electrode, and cathode electrode, such that at least one auxiliary electrode is provided between any two adjacent anode electrodes and cathode electrodes.

4. The method for seepage prevention and reinforcement of the soil surrounding a tunnel according to claim 3, characterized in that, Independent calcium source pipes and carbon source pipes are laid along the tunnel axis, wherein the calcium source pipes and the carbon source pipes are provided with openings including: Independent calcium source pipes and carbon source pipes are arranged along the tunnel axis. The calcium source pipe is arranged between the anode electrode and the auxiliary electrode, and the carbon source pipe is arranged between the auxiliary electrode and the cathode electrode. Openings are provided on the side of the calcium source pipe and the carbon source pipe facing the adjacent auxiliary electrode.

5. The method for seepage prevention and reinforcement of the soil surrounding a tunnel according to claim 4, characterized in that, The calcium source tube and the carbon source tube have openings on the side facing the adjacent auxiliary electrode, including: The calcium source tube and the carbon source tube have openings in the effective liquid release section corresponding to the auxiliary electrode. The effective liquid release section is a specific functional section on the calcium source tube and the carbon source tube facing the auxiliary electrode. The length of the effective liquid release section is 0.6m-1.0m, and the center position of the effective liquid release section corresponds to the auxiliary electrode. The remaining sections of the calcium source tube and the carbon source tube are fully enclosed structures.

6. The method for seepage prevention and reinforcement of the soil surrounding a tunnel according to claim 4, characterized in that, The diameter of the opening is 0.6mm-1.2mm; Along the tunnel axial direction, the distance between adjacent openings is 20mm-40mm; Along the circumferential direction of the calcium source tube or carbon source tube, the angle range of the opening is ≤120°.

7. The method for seepage prevention and reinforcement of the soil surrounding a tunnel according to claim 1, characterized in that, A drainage and venting hose is provided in parallel in the secondary grouting hole where the cathode electrode and the auxiliary electrode under negative bias are installed, so as to discharge the water and gas generated during the electrolysis process.

8. The method for seepage prevention and reinforcement of the soil surrounding a tunnel according to claim 1 or 2, characterized in that, The calcium source solution is a mixed aqueous solution comprising water-soluble calcium salt and nucleation regulator; The carbon source solution is an aqueous solution containing water-soluble carbonates.

9. The method for seepage prevention and reinforcement of the soil surrounding a tunnel according to claim 8, characterized in that, The concentration of the water-soluble calcium salt in the calcium source solution is 0.6 mol / L-1.5 mol / L; The concentration of the nucleating regulator in the calcium source solution is 0.5 g / L-10 g / L; The concentration of the water-soluble carbonate in the carbon source solution is 0.6 mol / L to 1.5 mol / L; Preferably, the water-soluble calcium salt includes calcium chloride; The nucleation regulator includes at least one of carboxymethyl chitosan, L-aspartic acid, and boric acid; The water-soluble carbonates include sodium carbonate.

10. The method for seepage prevention and reinforcement of the soil surrounding a tunnel according to claim 2, characterized in that, The release rates of the carbon source solution and the calcium source solution in the calcium source tube and the carbon source tube are determined according to the grade of the weak permeability region: In the slightly weak region, the release rate of the carbon source solution and the calcium source solution is 0.1 mL / min-0.2 mL / min, and the release time lasts for 4 h-6 h; In the moderately weak region, the release rate of the carbon source solution and the calcium source solution is 0.3 mL / min-0.4 mL / min, and the release time lasts for 6 h-8 h; In the severely weakened area, the release rate of the carbon source solution and the calcium source solution is 0.4 mL / min-0.5 mL / min, and the release time lasts for 8 h-10 h.

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