Construction method of preventing water burst by grouting in loose filling karst caves

Abstract

The present invention discloses a method for preventing water inrush by grouting loosely filled caves in tunnels. By zoning and managing water-rich caves, the water-rich nature of the caves is classified according to the different water yields from geophysical exploration and drilling. Furthermore, grouting materials are selected based on the water pressure, water volume, and physical properties of the different water-rich zones. This method achieves targeted and clear grouting of water-rich caves in karst areas, eliminating the drawbacks of previous methods, such as unfounded material selection, unclear planning, and unsatisfactory management results. The present invention solves the problems of existing cave grouting reinforcement slurries, such as uneven diffusion, incomplete solidification, and significant damage from dynamic water scour.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel construction, and in particular to a construction method for preventing water inrush by grouting a loose-filled karst cave through a tunnel. Background Art

[0002] During infrastructure construction in karst areas, especially tunnel construction in karst peak-valley geological and geomorphological zones, it is inevitable to cross various types of caves. Appropriate treatment measures are often required based on the distribution of the caves, their size, the presence of fillings, and whether there are any leaks. Caves are primarily filled in three states: fully filled, partially filled, or unfilled. Cave fillings are often hard, plastic, soft-plastic, or in a fluid-soft-plastic state. Loose fillings often contain high levels of water, making them prone to major disasters such as sudden water and mud inrush after tunnel excavation and penetration, impacting tunnel construction safety and schedule. The purpose of pretreatment for these caves is to reinforce the cave fillings and achieve a certain strength, preventing sudden water and mud inrush hazards from occurring in the tunnel after the loose fillings are exposed or cracks are penetrated.

[0003] This type of cave pretreatment construction usually adopts grouting reinforcement method, which is carried out before tunnel excavation or simultaneously with tunnel excavation construction. However, the existing cave grouting reinforcement has problems such as uneven slurry diffusion, incomplete solidification effect, and large amount of dynamic water erosion damage.

[0004] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the Invention

[0005] In order to overcome the defects of the existing technology, a tunnel loose filling cave grouting anti-water burst construction method is provided to solve the problems of uneven diffusion, incomplete solidification effect and large amount of dynamic water scouring damage of the existing cave grouting reinforcement slurry.

[0006] To achieve the above object, a method for preventing water inrush by grouting through a loose-filled cave is provided, comprising the following steps:

[0007] Use geophysical exploration and drilling to predict the development of karst caves ahead of the tunnel;

[0008] Based on the water inflow in the drilled borehole, the predicted water-rich caves are divided into strong water-rich areas, water-rich areas, and weak water-rich areas;

[0009] The strong water-rich area, the water-rich area and the weak water-rich area are treated in different zones, wherein the strong water-rich area is reinforced by grouting with polymer-modified cement-based slurry, ultrafine sulphoaluminate cement slurry or ester chemical slurry, the water-rich area is reinforced by grouting with polymer-modified cement-based slurry or double-liquid slurry, and the weak water-rich area is reinforced by grouting with single-liquid cement slurry;

[0010] The polymer-modified cement-based slurry comprises cement slurry, silica fume, polypropylene fiber and dispersible rubber powder, wherein the water-cement ratio of the cement slurry is 0.5-1, the amount of the silica fume is 5% of the volume of the cement slurry, the amount of the polypropylene fiber is 0.3% of the volume of the cement slurry, and the amount of the dispersible rubber powder is 0.3% of the mass of the cement slurry;

[0011] The ester chemical pulp comprises water glass, 1,4-butanediol, dibasic acid ester and water, wherein the mass ratio of water glass, 1,4-butanediol, dibasic acid ester and water is 100:7:8:85;

[0012] The double-liquid slurry includes cement slurry and water glass, and the volume ratio of the cement slurry to the water glass is 1 to 5:1.

[0013] Furthermore, during the grouting reinforcement process of the strong water-rich area, when the water inflow in the borehole drops to 1m 3 / h later, single-liquid cement slurry grouting reinforcement is used instead.

[0014] Furthermore, when single-liquid cement slurry is used for grouting reinforcement, a thin slurry is injected first. When the pressure does not rise after injecting the thin slurry for more than 30 minutes, the thick slurry is slowly adjusted. The water-cement ratio of the single-liquid cement slurry is 2:1 to 0.55:1. After the thick slurry is injected and the pressure increases, the thin slurry is adjusted until the grouting end standard is reached.

[0015] Furthermore, the water-cement ratio of the cement slurry in the polymer-modified cement-based slurry is 1.

[0016] Furthermore, during the grouting reinforcement process, a smaller grouting final pressure is used for shallow surrounding rock to prevent the surrounding rock from being damaged. As the stratum is reinforced from shallow to deep, the grouting final pressure is increased for deep surrounding rock.

[0017] Furthermore, during the grouting reinforcement process, a larger initial grouting rate is selected in the early stage of grouting. When the grouting pressure stabilizes, the grouting rate is gradually reduced according to a preset ratio to allow the low-rate slow seepage to fully strengthen the rock mass.

[0018] Furthermore, when using double-liquid grouting reinforcement, the grouting rate is reduced through intermittent grouting to increase the volume ratio of cement slurry to water glass, improve the slurry solidification reaction rate, and make the double-liquid slurry injected in advance gel to form a gel body in a wider structural surface, gradually reducing the cross-sectional area of the structural surface, and quickly achieve the sealing of the water-gushing structural surface.

[0019] Furthermore, the grouting interval time is less than 30s.

[0020] The beneficial effects of the present invention are that the tunneling loose-filled karst cave grouting construction method of the present invention prevents water inrush, including the steps of detecting the karst cave filling situation, analyzing the physical properties of the filling material, and conveying and injecting the slurry. The method adopts a polymer-modified cement-based slurry that is resistant to dynamic water scour, thereby achieving a new property of strong anti-scour performance that can block dynamic water and ductile destruction of the stone body at the cost of minimal reduction in the fluidity of the cement slurry. The solution-type strong permeability ester chemical slurry can be used for the reinforcement of silt silt fillings and water blocking in karst caves. The tunneling loose-filled karst cave grouting construction method of the present invention prevents water inrush by zoning and zoning the karst caves, dividing the water-richness of the karst caves according to the different water yields of geophysical exploration and drilling holes, and then matching the preferred slurry according to the water pressure, water volume and physical properties of the different water-rich areas, thereby achieving the targeted and clear grouting work of the water-rich filling karst caves in karst areas, and getting rid of the previous drawbacks of no basis for material use, unclear ideas and unsatisfactory treatment effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Other features, objects and advantages of the present application will become more apparent upon reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0022] Figure 1 Schematic diagram of the trial production steps of the polymer-modified cement-based slurry according to an embodiment of the present invention.

[0023] Figure 2 σ-ε curves of cement paste after solidification of polymer-modified cement-based slurries with different polypropylene fiber contents according to the embodiments of the present invention.

[0024] Figure 3 σ-ε curves of cement paste after solidification of polymer-modified cement-based slurries with different silica fume contents according to the embodiments of the present invention.

[0025] Figure 4 This is a graph showing the compressive strength of cement paste after consolidation of the polymer-modified cement-based slurry and ordinary Portland cement slurry according to an embodiment of the present invention.

[0026] Figure 5 This is a structural diagram of the anti-dispersion test of the polymer-modified cement-based slurry according to an embodiment of the present invention.

[0027] Figure 6 FIG. 4 is a time-varying viscosity curve of the ester chemical pulp according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the relevant invention and are not intended to limit the invention. It should also be noted that, for ease of description, only portions relevant to the invention are shown in the accompanying drawings.

[0029] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0030] Reference Figures 1 to 6 As shown, the present invention provides a construction method for preventing water inrush by grouting in a loose-filled cave, comprising the following steps:

[0031] S1: Use geophysical exploration and drilling to predict the development of karst caves in front of the tunnel.

[0032] First, geophysical exploration was conducted. Specifically, geological radar detection and transient electromagnetic methods were used, combined with horizontal drilling, to rapidly and accurately measure the development of karst caves within 30 meters ahead of the tunnel during excavation.

[0033] The reflected waveform of geological radar is mainly composed of medium and high frequency signals, with strong amplitude, irregular waveform, discontinuous phase axis, and developed karst fissures, obvious dissolution phenomenon, and the existence of unfilled caves.

[0034] If the low resistance measured by the transient electromagnetic method is obvious, the probability of the cave being filled with water is very high.

[0035] If the reflected signal wave of the geological radar is relatively uniform, or the high and low resistance ranges measured by the transient electromagnetic method are not clear, additional drilling is required to further clarify the filling and water content.

[0036] Through a comprehensive method, the distribution, location, burial depth, size, and volume of caves, cracks, and groundwater can be effectively predicted, and the three-dimensional irregular morphology of hidden caves can be visualized. Clustered caves, beaded caves, and super-long caves can be identified. Unfilled caves, semi-filled caves with fluidized clay containing crushed stone, and fully filled caves can be identified, providing strong data support for the formulation of targeted complex karst filling grouting construction plans.

[0037] For karst caves in front of or to the side of the tunnel face that have been initially shown to have water-rich fillings by geophysical exploration or drilling but have not been exposed by tunnel excavation, further drilling sampling is required to conduct visual and indoor permeability tests to evaluate the physical properties of the fillings using a combination of qualitative and quantitative methods.

[0038] For caves revealed by tunnel excavation, if sampling is possible, then sampling analysis and testing will be conducted in the caves, and the necessity of grouting and sealing will be determined based on the geological survey results.

[0039] S2: Based on the water inflow in the drilled borehole, the predicted water-rich caves are divided into strong water-rich areas, water-rich areas, and weak water-rich areas.

[0040] In this invention, the concept of zoning and zoning management of cave water-rich areas is proposed. First, the water-rich nature of the cave is divided according to the different water yields of geophysical exploration and drilling holes. Specifically, the cave is divided into strong water-rich areas (drilling water yield> 10m 3 / h, with a certain pressure or flow rate), water-rich areas (drilling water flow of 1 to 10m 3 / h) and weak water-rich areas (borehole water inflow <1m 3 / h).

[0041] S3: Zoning and management of strong water-rich areas, water-rich areas and weak water-rich areas. For the strong water-rich areas, polymer modified cement-based slurry, ultrafine sulphoaluminate cement slurry or ester chemical slurry grouting reinforcement is adopted; for the water-rich areas, polymer modified cement-based slurry or double-liquid slurry grouting reinforcement is adopted; for the weak water-rich areas, single-liquid cement slurry grouting reinforcement is adopted.

[0042] In the present invention, different slurry materials are used for different partitions with different water-rich properties.

[0043] Specifically, the slurry materials include polymer modified cement-based slurry, ultrafine sulphoaluminate cement slurry, ester chemical slurry, two-liquid slurry (two-liquid type cement slurry), and single-liquid cement slurry (single-liquid type cement slurry). See Table 1 for the characteristics and applicable occasions of the slurry materials.

[0044] Table 1. Slurry reservoir and slurry characteristics and applicable conditions

[0045]

[0046] Among them, the polymer modified cement-based slurry includes cement slurry, silica fume, polypropylene fiber and dispersible rubber powder. The water-cement ratio of the cement slurry is 0.5-1, the amount of silica fume is 5% of the volume of the cement slurry, the amount of polypropylene fiber is 0.3% of the volume of the cement slurry, and the amount of dispersible rubber powder is 0.3% of the mass of the cement slurry.

[0047] As a preferred embodiment, the water-cement ratio of the cement slurry in the polymer-modified cement-based slurry is 1.

[0048] The preparation process of polymer modified cement-based slurry is shown in Figure 1 As shown in the figure, by conducting experimental studies on different addition amounts, the optimal composite ratio scheme was obtained, and the dynamic water treatment effect was evaluated by introducing the loss rate PER indicator.

[0049] See Figure 2The addition of PP (polypropylene) fiber and silica fume to the polymer-modified cement-based slurry on the basis of cement-based materials can significantly improve the ductility and strength characteristics of ordinary cement slurry. The addition of PP fiber can make the slurry form a network overlap in the karst loose material, greatly enhancing the ductility, making it more stable during tunnel excavation disturbance and less prone to landslide.

[0050] See Figure 3 The addition of a small amount of silica fume can significantly improve the bonding strength of the slurry after solidification, making the karst loose body more reinforced.

[0051] Further tests and comparisons show that the compressive strength and flexural strength of polymer-modified cement-based materials are about 30% and 40% higher than those of conventional cement slurry materials. Figure 4 As shown in Table 2, it has greater advantages in strength characteristics and has good improvement characteristics for filling and reinforcing loose materials in caves, ensuring the safe excavation of tunnels passing through caves.

[0052] Table 2. Strength test of polymer modified cement-based slurry and ordinary Portland cement slurry

[0053]

[0054] In addition to ensuring the strength of the material, the polymer modified cement-based grout is further improved for its anti-dynamic water properties by adding polymer latex powder to form a paste-like anti-dispersion grouting material. Figure 5 As shown in Table 3, ordinary cement slurry retains only about 0-30% at high flow rates above 0.4 m / s, with the vast majority lost. The newly developed paste-like slurry exhibits excellent anti-dispersion properties. By adjusting the water-cement ratio at flow rates above 0.4 m / s, it can achieve a retention rate of over 80%, meeting project requirements. This performance is significantly improved compared to ordinary cement slurry, with the maximum improvement exceeding three times.

[0055] Table 3. Anti-dispersion test results of polymer-modified cement-based materials and ordinary Portland cement materials

[0056]

[0057] Table 3. Anti-dispersion test results of polymer-modified cement-based materials and ordinary Portland cement materials

[0058]

[0059] The preparation method of the polymer modified cement-based slurry of the present invention is:

[0060] a. Weigh each component material according to the designed water-cement ratio (W / C) (1:1) and the modified admixture. The recommended amount of PP fiber is 0.3% of the cement slurry volume, silica fume is 5% of the cement volume, and dispersible polymer powder is 3‰ of the cement mass.

[0061] b. Mix all powders evenly. It is recommended to dry mix for 2 minutes, then add the weighed water and stir thoroughly to prepare a slurry for later use. The recommended stirring time is 3 to 5 minutes.

[0062] In the present invention, the ester chemical pulp comprises water glass, 1,4-butanediol, a dibasic acid ester, and water, wherein the mass ratio of water glass, 1,4-butanediol, dibasic acid ester, and water is 100:7:8:85. The water glass of the ester chemical pulp is liquid A, and the 1,4-butanediol and dibasic acid ester form liquid B.

[0063] The ester chemical slurry of the present invention is in solution form, free of particles, has excellent permeability, and has an adjustable curing time. The ester chemical slurry of the present invention can cure crushed bodies with small pores / crack channels and extremely low permeability, as well as fine sand fillings.

[0064] The proportion and preparation method of the ester chemical pulp of the present invention are as follows:

[0065] The solution consists of Liquid A and Liquid B in a 1:1 volume ratio. Liquid A is a stock solution of water glass, and Liquid B is a mixed solution of 1,4-butanediol and a dibasic acid ester. The specific ratio is water glass: catalyst: curing agent: water = 100:7:8:85. With this ratio, the solution initially appears as a colorless, transparent liquid. White turbidity develops at 209 seconds, flocculation begins at 262 seconds, initial clumps form at 287 seconds, and a stone-like gelation begins at 595 seconds. After prolonged standing, it solidifies, achieving a relatively high hardness.

[0066] The ester chemical pulp of the present invention is a solution type lipid chemical pulp, and its viscosity time-varying curve is as follows: Figure 6 As shown in the time-varying viscosity curve of the ester chemical slurry of the present invention, it can be seen that the slurry viscosity is very low before about 400 seconds and increases exponentially at a relatively low rate. After 400 seconds, an inflection point appears and the viscosity increases rapidly, indicating that the slurry cements and solidifies very quickly.

[0067] The double-liquid slurry includes cement slurry and water glass, and the volume ratio of cement slurry to water glass is 1 to 5:1.

[0068] During the grouting reinforcement process of the strong water-rich area, when the water inflow in the borehole drops to 1m 3 / h later, single-liquid cement slurry grouting reinforcement is used instead.

[0069] When using single-liquid cement slurry for grouting reinforcement, first inject thin slurry. When the pressure does not rise after injecting the thin slurry for more than 30 minutes, slowly adjust the slurry to thicken it. The water-cement ratio of the single-liquid cement slurry is 2:1 to 0.55:1. After the thick slurry is injected and the pressure rises, adjust the slurry to thin until the grouting end standard is reached.

[0070] During the grouting reinforcement process, a smaller grouting final pressure is used for shallow surrounding rock to prevent the surrounding rock from being damaged. As the stratum is reinforced from shallow to deep, the grouting final pressure is increased for deep surrounding rock.

[0071] During the grouting reinforcement process, a larger initial grouting rate is selected in the early stage of grouting. When the grouting pressure stabilizes, the grouting rate is gradually reduced according to the preset ratio to allow low-rate slow seepage to fully strengthen the rock mass.

[0072] When using double-liquid grouting reinforcement, the grouting rate is reduced through intermittent grouting to increase the volume ratio of cement slurry to water glass, improve the slurry solidification reaction rate, and make the double-liquid slurry injected in advance gel to form a gel body in a wider structural surface, gradually reducing the cross-sectional area of the structural surface, which can quickly achieve the sealing of the water-gushing structural surface.

[0073] The interval time of double-liquid grouting is less than 30s.

[0074] The selection of several grouting materials used in the present invention mainly follows the principles:

[0075] Grouting purpose matching principle: Single-liquid slurry is used for grouting in caves with reinforcement as the main purpose, and double-liquid slurry or polymer-modified cement-based slurry is used for grouting in caves with water blocking as the main purpose.

[0076] Slurry particle size matching principle: that is, considering the particle size of the grouting material, ordinary cement-based materials are used for soft and broken fillings, and ultra-fine or chemical grouting materials are used for sand layer fillings with low-flow groundwater.

[0077] The principle of hydrological matching of filling materials in caves: single-liquid slurry is used in weak water-rich areas, and double-liquid slurry, polymer-modified cement-based slurry and polyurethane chemical slurry are used in high-pressure and strong water-rich areas.

[0078] Principles of dynamic adjustment of grouting process: If the filling material has complex particle composition, dynamic adjustment shall be made according to the three criteria of from coarse to fine, from single to double, and from high concentration to low concentration.

[0079] Based on the actual geological and hydrogeological conditions of the tunnel or cave it passes through, a gradient-controlled grouting process is employed. Grouting pressure, grouting rate, and the time-varying characteristics of the slurry are key factors in controlling the migration and diffusion of slurry within the geotechnical medium. By rationally adjusting and controlling these three factors through controlled grouting measures, controlled diffusion of slurry within different filling materials can be achieved, avoiding uncontrolled and disordered flow and diffusion under fixed parameters.

[0080] The reasonable evaluation of grouting effect is an important part of grouting work. The evaluation methods of grouting reinforcement effect applicable to the actual construction site mainly include analytical method, inspection hole method and geophysical method.

[0081] The analysis method organizes and analyzes the information collected during the grouting process to conduct a quick and direct qualitative and quantitative evaluation of the grouting effect, including the grouting pressure P-grouting volume Q-grouting time t (PQt) curve method monitored during the grouting process and the comparison of water inflow before and after grouting.

[0082] The inspection hole method primarily refers to inspection hole coring. After grouting is completed, the grouting effect is evaluated by coring and permeability coefficient measurement through inspection holes at key monitoring locations based on the distribution of grouting volume. Generally speaking, the number of inspection holes should be 3% to 5% of the total number of drilled holes, with no fewer than three. For high-pressure, water-rich formations, the number of inspection holes should be 5% to 10% of the total number of drilled holes.

[0083] The geophysical method can evaluate the grouting effect at a macro level, especially the comparison of geophysical results before and after grouting, which can be used to evaluate the grouting effect very well.

[0084] In practice, the testing and evaluation methods must be determined based on the site conditions; drilling and geophysical exploration are recommended. Engineering experience shows that grouting with a thickness of 3m or more can significantly reduce water inflow from the cave filling.

[0085] The tunnel loose filling grouting anti-water burst construction method of the present invention includes the steps of cave filling condition detection, filling material physical property analysis, slurry transportation and injection, etc., and adopts polymer modified cement-based slurry that is resistant to dynamic water scour, so as to achieve the new performance of strong anti-scour performance that can block dynamic water and ductile destruction of stone body at the cost of extremely small reduction in cement slurry fluidity; solution-type strong penetration ester chemical slurry can be used for reinforcement of silt silt filling and cave water blocking.

[0086] The tunnel loose filling karst cave grouting anti-water burst construction method of the present invention divides the karst cave water-rich zone and zoning management, divides the karst cave water-richness according to the different water yields of geophysical exploration and drilling holes, and then matches the preferred slurry according to the water pressure, water volume and physical properties in different water-rich areas, thereby achieving the targeted and clear grouting work of water-rich filling caves in karst areas, and getting rid of the previous drawbacks of no basis for material use, unclear ideas and unsatisfactory management effects.

[0087] In addition, the present invention's tunnel loose filling grouting to prevent water bursting construction method proposes a gradient controlled grouting process. By controlling the grouting pressure gradient, grouting rate gradient and interval time, the controlled diffusion of slurry in the cave filling and soft and broken surrounding rock is achieved, avoiding the disorderly diffusion of slurry to adapt to different site realities and working conditions, greatly broadening the tunnel excavation water-rich zone, loose area grouting reinforcement construction method and water bursting prevention effect, and reducing the blind loss and waste of slurry.

[0088] The above description is merely a preferred embodiment of the present application and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of the invention herein is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the inventive concept. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features having similar functions disclosed in this application.

Claims

1. A construction method for preventing water inrush by grouting loose-filled caves in tunnels, characterized in that: The following steps are involved: Use geophysical exploration and drilling to predict the development of karst caves ahead of the tunnel; Based on the water inflow in the drilled borehole, the predicted water-rich caves are divided into strong water-rich areas, water-rich areas, and weak water-rich areas; The strong water-rich area, the water-rich area and the weak water-rich area are treated in different zones, wherein the strong water-rich area is reinforced by grouting with polymer-modified cement-based slurry, ultrafine sulphoaluminate cement slurry or ester chemical slurry, the water-rich area is reinforced by grouting with polymer-modified cement-based slurry or double-liquid slurry, and the weak water-rich area is reinforced by grouting with single-liquid cement slurry; The polymer-modified cement-based slurry comprises cement slurry, silica fume, polypropylene fiber and dispersible rubber powder, wherein the water-cement ratio of the cement slurry is 0.5-1, the amount of the silica fume is 5% of the volume of the cement slurry, the amount of the polypropylene fiber is 0.3% of the volume of the cement slurry, and the amount of the dispersible rubber powder is 0.3% of the mass of the cement slurry; The ester chemical pulp comprises water glass, 1,4-butanediol, dibasic acid ester and water, wherein the mass ratio of water glass, 1,4-butanediol, dibasic acid ester and water is 100:7:8:85; The double-liquid slurry includes cement slurry and water glass, and the volume ratio of the cement slurry to the water glass is 1 to 5:1; During the grouting reinforcement process of the strong water-rich area, when the water inflow in the borehole drops to 1m 3 / h later, single-liquid cement slurry grouting reinforcement was used instead; When using single-liquid cement slurry for grouting reinforcement, first inject a thin slurry. When the pressure does not rise after injecting the thin slurry for more than 30 minutes, slowly adjust the slurry to a thick slurry. The water-cement ratio of the single-liquid cement slurry is 2:1 to 0.55:

1. After the thick slurry is injected and the pressure rises, adjust the slurry to a thin slurry until the grouting end standard is reached.

2. The method for preventing water inrush by grouting loose-filled caverns in tunnels according to claim 1, characterized in that: The water-cement ratio of the cement slurry in the polymer-modified cement-based slurry is 1.

3. The method for preventing water inrush by grouting through loose-filled caverns in tunnels according to claim 1, characterized in that: During the grouting reinforcement process, a smaller grouting final pressure is used for shallow surrounding rock to prevent the surrounding rock from being damaged. As the stratum is reinforced from shallow to deep, the grouting final pressure is increased for deep surrounding rock.

4. The method for preventing water inrush by grouting through loose-filled caverns in a tunnel according to claim 1, characterized in that: During the grouting reinforcement process, a larger initial grouting rate is selected in the early stage of grouting. When the grouting pressure stabilizes, the grouting rate is gradually reduced according to the preset ratio to allow low-rate slow seepage to fully strengthen the rock mass.

5. The method for preventing water inrush by grouting through loose-filled caverns in tunnels according to claim 1, characterized in that: When using double-liquid grouting reinforcement, the grouting rate is reduced through intermittent grouting to increase the volume ratio of cement slurry to water glass, improve the slurry solidification reaction rate, and make the double-liquid slurry injected in advance gel to form a gel body in a wider structural surface, gradually reducing the cross-sectional area of the structural surface, which can quickly achieve the sealing of the water-gushing structural surface.

6. The method for preventing water inrush by grouting through loose-filled caverns in a tunnel according to claim 5, characterized in that: The grouting interval time is less than 30s.

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